Special Report. Exercise Standards. to grade since the response to activation of a

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1 2286 AIL4 Medical/Scientific Statement Special Report Exercise Standards A Statement for Health Professionals From the American Heart Association Writing Group Gerald F. Fletcher, MD, Chairman; Victor F. Froelicher, MD; L. Howard Hartley, MD; William L. Haskell, PhD; and Michael L. Pollock, PhD T he purpose of this report is to provide standards and guidelines for exercise testing and training of persons free of clinical manifestations of cardiovascular disease and those with known cardiovascular disease. They are directed to and appropriate for physicians, nurses, exercise specialists, technologists, and other health professionals involved in regular exercise testing and training of these populations. These standards and guidelines coincide with the American Heart Association's "Statement on Exercise" published in Circulation (1990;81: ). These guidelines constitute a revision of earlier publications of the American Heart Association (AHA) that addressed the issues of exercise testing and training. Background and scientific rationale are provided and issues of practical importance in the clinical use of these standards are considered. Selected references are included. Exercise Testing The Cardiovascular Response to Exercise Exercise, a common physiological stress, can elicit cardiovascular abnormalities not present at rest and can be used to determine the adequacy of cardiac function. Exercise is only one of many stresses to which humans can be exposed; therefore, it is more appropriate to call an "exercise" test exactly that and not a "stress test." Types of exercise Two types of muscular contraction or exercise can be applied as a stress to the cardiovascular system: Isometric (static) or isotonic (dynamic).1 Isometric exercise, defined as a constant muscular contraction without movement (e.g., handgrip), imposes greater pressure than volume load on the left ventricle in "Exercise Standards" was approved by the American Heart Association Steering Committee on February 21, Correspondence should be sent to the Office of Scientific Affairs, American Heart Association, 7320 Greenville Avenue, Dallas, TX relation to the body's ability to supply oxygen. The cardiovascular response to isometric exercise is difficult to grade since the response to activation of a small muscle group is similar to the response to a large muscle group. In addition, cardiac output is not increased as much since increased resistance in active muscle groups limits blood flow. Isotonic exercise, defined as muscular contraction resulting in movement, primarily provides a volume load to the left ventricle, and the cardiovascular response is proportional to the severity of the exercise. Key Point: Dynamic exercise is preferred for testing because it puts a volume stress rather than a pressure stress on the heart and it can be graduated. However, most activities usually combine, in varying degrees, both types of exercise. Maximum oxygen uptake When dynamic exercise is begun, oxygen uptake by the lungs quickly increases. After the second minute, oxygen uptake usually remains relatively stable (steady state) at each intensity of exercise. During a steady state, heart rate, cardiac output, blood pressure, and pulmonary ventilation are maintained at reasonably constant levels.1 V 2 max is the greatest amount of oxygen a person can use while performing dynamic exercise involving a large part of total muscle mass.2 Vo2 max represents the amount of oxygen transported and used in cellular metabolism. It is convenient to express oxygen uptake in multiples of sitting, resting requirements. The metabolic equivalent (MET) is a unit of sitting, resting oxygen uptake (3.5 ml 02 per kilogram of body weight per minute [ml. kg` * min-1]). Rather than determining each person's true resting oxygen uptake, a MET is taken as this average. Vo2 ma, is significantly related to age, gender, exercise habits, heredity, and cardiovascular clinical status. Age: Maximum values of V02 max occur between ages 15 and 30, decreasing progressively with age. At age 60, mean Vo2 max in men is approximately three fourths that at age 20. With a sedentary lifestyle,

2 TABLE 1. Clinically Significant Key Metabolic Equivalents for Maximum Exercise 1 MET=resting 2 METs=level walking at 2 mph 4 METs=level walking at 4 mph <5 METs=poor prognosis; usual limit immediately after myocardial infarction; peak cost of basic activities of daily living 10 METs=prognosis with medical therapy as good as coronary artery bypass surgery 13 METs=excellent prognosis regardless of other exercise responses 18 METs=elite endurance athletes 20 METs=world class athletes MET, metabolic equivalent or a unit of sitting, resting oxygen uptake. 1 MET=3.5 ml* kg`1 min-1 oxygen uptake. there is a 9% reduction per decade versus less than 5% per decade for an active lifestyle. Gender: Up to age 12-16, there is no significant difference in V02 max among children. At age 12-14, a decrease is observed in girls. Reduced Vo2 max in women is attributed to smaller muscle mass, lower hemoglobin and blood volume, and smaller stroke volume as compared with men. Exercise habits: Physical activity has an important influence on Vo2 max. After 3 weeks of bed rest, there is a 25% decrease in Vo2 max in healthy men. In moderately active young men, Vo2 max is about 12 METs, whereas individuals performing aerobic training such as distance running can have a Vo2 max as high as METs (60-85 ml kg`. min'). Heredity: There is a natural variation in Vo2 max related to genetic factors. Cardiovascular clinical status: V02 max is affected by the degree of impairment caused by disease. It is difficult to accurately predict Vo2 max from its relation to exercise habits and age because of considerable scatter and correlations that are generally low. Table 1 lists key values of METs that are TABLE 2. Normal Values of Maximum Oxygen Uptake at Different Ages* Age Men Women (±22) 36 (±21) [12 METs] [10 METs] (±22) 34 (±21) [12 METs] [10 METs] (±22) 32 (±21) [11 METs] [9 METs] (±22) 29 (±22) [10 METs] [8 METs] (-22) 27 (±22) [9 METs] [8 METs] (+22) 27 (±22) [8 METs] [8 METs] *(ml kg`-1 min-1) MET, metabolic equivalent; 1 MET=3.5 ml * kg-1- min1 Oxygen uptake. TABLE 3. Writing Group Exercise Standards 2287 Determinants and Methods of Measuring Ventilatory and Myocardial Oxygen Consumption Vo2 max measured by analysis of expired air or estimated from work load achieved Vo2 max=cardiac output (HR x SV) x avo2 difference Mo2 determined by wall tension (LV pressure xlv volume), contractility, and HR. Measurement requires catheterization. Mo2 estimated by HRxsystolic blood pressure (double product) *avo2 difference cannot exceed ml % at maximum exercise; therefore, Vo2 max is a noninvasive method for estimating cardiac output. Vo2, oxygen uptake; Vo2 max, maximum oxygen uptake; Mo2, myocardial oxygen uptake; avo2, arteriovenous oxygen difference; LV, left ventricular; HR, heart rate; SV, stroke volume. clinically relevant, and Table 2 depicts normal values for age. Maximum Vo2 is equal to maximum cardiac output times maximum arteriovenous oxygen (avo2) difference. Since cardiac output is equal to the product of stroke volume and heart rate, Vo2 is directly related to heart rate. The maximum avo2 difference during exercise has a physiological limit of volumes percent; hence, if maximum effort is achieved, Vo2 max can be used to estimate maximum cardiac output. Myocardial oxygen uptake Myocardial oxygen uptake (Mo2) is determined by intramyocardial wall tension (left ventricular [LV] systolic pressure times end-diastolic volume, divided by LV wall thickness), contractility, and heart rate. Other less important factors include external work performed by the heart, the energy necessary for activation, and the basal metabolism of the myocardium (Table 3). Accurate measurement of Mo2 requires cardiac catheterization. Mo2 can be estimated during clinical exercise testing by the product of heart rate and systolic blood pressure, called the double product or rate pressure product. There is a linear relation between Mo2 and coronary blood flow. During exercise, coronary blood flow increases as much as fivefold above the resting value. A patient with obstructive coronary disease often cannot produce enough coronary blood flow to supply the metabolic demands of the myocardium during vigorous exercise, and as a consequence, myocardial ischemia occurs. Angina pectoris usually occurs at the same double product rather than at the same external work load. Key Point: An important basic principle of exercise physiology is that Vo2 and Mo2 have distinct determinants and methods of measurement or estimation (Table 3). Although they are directly related, this relation can be altered, for example, by training and,l-blockers. Response to dynamic exercise The body's response to dynamic exercise consists of a complex series of cardiovascular adjustments to provide active muscles with the blood supply appropriate for their metabolic needs, to dissipate the heat generated by active muscles, and to maintain the blood supply to the brain and the heart.

3 2288 Special Report Circulation Vol 82, No 6, December THE RESPONSE OF HEALTHY MEN TO TREADMILL EXERCISE P - FIGURE 1. Normal response to progressive treadmill protocol in healthy subjects. From Froelicher - VF: Exercise and the Heart: Clinical Concepts. Chicago, Year Book Medical Publishers, Inc, 1987, p 102. Reproduced with pennission. t ii g01h P*rceniile 80 _ Diestolic Blqod Pressurq (mmh) i l! -I 1/3 MAX 2/3 MAX AGE (years) As cardiac output increases with dynamic exercise, peripheral resistance increases in tissues that do not function during exercise and decreases in active muscles.3 Arterial blood pressure increases only mildly; thus, flow can increase as much as fivefold. Since the denominator (flow) increases much more than the numerator (pressure) in the formula for resistance, the result is a decrease in systemic vascular resistance. Heart rate response An increase in heart rate due to a decrease in vagal outflow is an immediate response of the cardiovascular system to exercise, and is followed by an increase in sympathetic outflow to the heart and systemic blood vessels. During dynamic exercise, heart rate increases linearly with work load and Vo2. During low levels of exercise and at a constant work rate, heart rate will reach steady state within several minutes. As work load increases, time to stabilize will progressively lengthen. Heart rate response is influenced by several factors, including age. There is a decline in mean maximum heart rate with age,4 which appears to be related to intrinsic cardiac changes rather than neural influences. Dynamic exercise increases heart rate more than isometric exercise. An accentuated heart rate response is observed after bed rest. Other factors that influence heart rate include body position, physical conditions, state of health, blood volume, and environment. Key Point: Heart rate response to maximum dynamic exercise is dependent on numerous factors, but particularly age and health. Although a regression line of 220-age is fairly reproducible, the scatter around this line is sizable (1 SD=12 beats/min), making agepredicted maximum heart rate relatively limited for clinical purposes. Arterial blood pressure response Systolic blood pressure rises with increasing dynamic work as a result of increasing cardiac output, iereas diastolic pressure usually remains about the ne. Normal values of maximum systolic blood sssure for men have been defined and are directly lated to age. An inadequate rise in systolic blood pressure )-30 mm Hg or less) can result from aortic outflow struction, left ventricular dysfunction, or ischemia. ianges of blood pressure reflect more than the ntractile function of the left ventricle since they ;o depend on peripheral resistance. Patients who velop hypotension during exercise frequently have vere heart disease; patients with valvular disease n also exhibit a drop in systolic blood pressure. After maximum exercise, there normally is a decline systolic blood pressure, usually reaching resting 'els in 6 minutes, then often remaining lower than eexercise levels for several hours. In some patients th coronary artery disease (CAD), higher levels of,tolic blood pressure exceeding peak exercise values ve been observed in the recovery phase. When ercise is terminated abruptly, some healthy persons,e precipitous drops in systolic blood pressure due venous pooling. Figure 1 shows the physiological response to bmaximum and maximum treadmill exercise Lsed on tests of more than 700 apparently healthy mn aged Maximum double product (heart te times systolic blood pressure) ranges from a nth percentile value of 25,000 to a 90th percentile lue of 40,000. sting Procedures e physician's role Exercise testing should be conducted only by welltined personnel with a basic knowledge of exercise ysiology. Only technicians and physicians familiar th normal and abnormal responses during exercise n recognize or prevent untoward events. Equipent, medications, and personnel trained to provide

4 TABLE 4. Complications Secondary to Exercise Tests Cardiac Bradyarrhythmias Sinus Atrioventricular junctional Ventricular Atrioventricular block Asystole Sudden death (ventricular tachycardia/fibrillation) Myocardial infarction Congestive heart failure Hypotension and shock Noncardiac Musculoskeletal trauma Ill-defined and miscellaneous Severe fatigue, dizziness, fainting, general malaise, body aches, delayed ill feelings, and fatigue sometimes persisting for days cardiopulmonary resuscitation (CPR) must be readily available. Although exercise testing is considered a safe procedure, there are reports of acute infarctions and deaths. Multiple surveys confirm that up to 10 myocardial infarctions or deaths or both can be expected per 10,000 tests. However, the relative risk of an adverse event during an exercise test versus during usual activity of patients with CAD is estimated to be 60- to 100-fold. Risk is greater in the postmyocardial infarction patient and in those being evaluated for malignant ventricular arrhythmias. Table 4 lists three classes of complications secondary to exercise tests. TABLE 5. Absolute and Relative Contraindications to Exercise Testing Absolute Acute myocardial infarction or recent change on resting electrocardiogram Active unstable angina Serious cardiac arrhythmias Acute pericarditis Endocarditis Severe aortic stenosis Relative* Less serious noncardiac disorder Significant arterial or pulmonary hypertension Tachyarrhythmias or bradyarrhythmias Moderate valvular or myocardial heart disease Drug effect or electrolyte abnormalities Left main coronary obstruction or its equivalent Hypertrophic cardiomyopathy Severe left ventricular dysfunction Acute pulmonary embolus or Psychiatric disease pulmonary infarction Acute or serious noncardiac disorder Severe physical handicap or disability *Under certain circumstances and with appropriate precautions, relative contraindications can be superseded. Writing Group Exercise Standards 2289 Good clinical judgment should be foremost in deciding indications and contraindications for exercise testing.5 Whereas absolute contraindications are definitive, in selected cases with relative contraindications, even submaximum testing can provide valuable information. Table 5 lists absolute and relative contraindications to exercise testing. In any procedure with a risk of complications, the physician should be certain that the subject understands the situation and acknowledges the risks. Some physicians believe that informing patients of possible risks may cause them to become anxious or discourage them from undergoing a test. This possibility and the fact that a signed consent form does not protect a physician from legal action have recently led to less insistence on obtaining written consent. However, if consent is not initially obtained, a physician may be held responsible for a major adverse event, even if the test is carefully performed. The argument can be made that the patient would not have undergone the procedure if he or she had been aware of the risks associated with the test. Good physician-patient communication about testing is mandatory. Exercise testing should be performed under the supervision of a physician who is appropriately trained to conduct exercise tests. The physician should be responsible for ensuring that the exercise laboratory is properly equipped and that exercise testing personnel are appropriately trained. The degree of patient supervision needed during a test can be determined by the clinical status of the patient being tested. Supervision must be decided by the physician or physician's assistant, who asks pertinent questions about the patient's medical history, performs a brief physical examination, and reviews the standard 12-lead electrocardiogram (ECG) performed immediately before testing. The physician should interpret data derived from testing, suggest further evaluation or therapy, and help deliver effective and timely advanced CPR when necessary. The physician must be trained in advanced CPR. A defibrillator and appropriate medications should also be available. The degree of supervision can range from assigning monitoring of the test to a properly trained nonphysician (i.e., nurse or exercise specialist) for testing apparently healthy younger persons (less than 40 years old) and those with stable chest pain syndromes to the physician who directly monitors the patient's blood pressure and status throughout exercise and recovery. The latter is the ideal for testing patients for diagnostic or prognostic purposes and is certainly a requirement for testing all patients at increased risk for exercise-induced complications. A physician should be immediately available during all exercise tests. Patient preparation Preparations for exercise testing include the following:

5 2290 Special Report Circulation Vol 82, No 6, December 1990 * The patient should be instructed not to eat or smoke for 3 hours before the test and to dress appropriately for exercise. No unusual physical efforts should be performed for at least 12 hours before testing. If thallium-201 imaging is to be performed with testing, the patient should be told not to eat for 8 hours before testing. * A brief history and physical examination should be performed to rule out contraindications to testing or to detect important clinical signs such as cardiac murmur, gallop sounds, pulmonary bronchospasm, or rales. Patients with a history of increasing or unstable angina or heart failure should not undergo exercise testing until their condition stabilizes. A cardiac physical examination should indicate which patients have valvular or congenital heart disease, particularly those with severe aortic stenosis who should not undergo exercise testing. * Withdrawal of medications may be considered since some drugs interfere with exercise responses, complicating interpretation of exercise testing. There are no formal guidelines for tapering medications, but rebound phenomena may occur with discontinuance of [3-blockers. Therefore, most patients are tested while taking their usual medications. Specific questioning is important to determine which drugs have been taken so that the physician can be aware of possible electrolyte abnormalities and other effects. * If the reason for the exercise test is not clear, the patient should be questioned and the referring physician contacted. * A resting 12-lead ECG should be obtained since it may differ from the resting preexercise ECG. This is essential, particularly in patients with known heart disease, since an abnormality or a change may contraindicate testing. Recording the ECG before starting the exercise test and after hyperventilation at another time may be helpful in detecting a falsepositive ECG change. * Standing ECG and blood pressure should be recorded to determine vasoregulatory abnormalities, particularly ST depression. * A detailed explanation of the testing procedure should be given, outlining risks and possible complications. The patient should be told how to perform the exercise test and the testing procedure should be demonstrated. Electrocardiographic recording Skin preparation. The most critical point of the electrode-amplifier-recording system is the interface between electrode and skin. Removal of the superficial layer of skin significantly lowers its resistance, decreasing the signal-to-noise ratio. The areas for electrode application are first shaved and then rubbed with an alcohol-saturated gauze. After the skin dries, it is marked with a felt-tip pen and rubbed with a fine sandpaper or rough material. With these procedures, skin resistance should be reduced to 5,000 Ql or less. Electrodes and cables. Many electrodes are available for performing exercise testing. Silver plate or FIGURE 2. Negative electrode placement for most bipolar lead systems. B, on back subscapular; M, top of manubrium; X, midaxillary line, fifth intercostal level; C, anterior axillary line, fifth intercostal level; H, above shoulders (neck or above); S, right clavicular edge; R, right arm; +, positive electrode placement for C5 bipolar electrodes. From Froelicher VF: Exercise and the Heart: Clinical Concepts. Chicago, Year Book Medical Publishers, Inc, 1987, p 18. Reproduced with permission. silver chloride crystal pellets are best since they have the lowest offset voltage. The electrodes should be constructed with a metal interface that is sunken, creating a column to be filled with either an electrolyte solution or a saturated sponge. When using fluid column electrodes, direct metal-to-skin contact should be avoided, decreasing motion artifact. Connecting cables between the electrodes and recorder should be light, flexible, and properly shielded. Most available commercial exercise cables are constructed to lessen motion artifact. Cables generally have a life span of a year or so, depending on use. They eventually become a source of both noise and electrical discontinuity and must be replaced. Lead systems. Bipolar leads. Bipolar lead systems were the first to be used to detect ECG changes during exercise. The relatively short placement time, freedom from motion artifacts, and the ease with which noise problems can be located are factors that favor their use. The usual positive reference is an electrode placed in the same position as the positive reference for V5 (the fifth intercostal space at the midclavicular line). The negative reference for V5 is Wilson's central terminal. Figure 2 illustrates negative electrode placement for most bipolar lead systems. CM5 is the most sensitive for ST segment changes. CC5 excludes the vertical component included in CM5 and decreases influence of atrial repolarization (Ta), reducing falsepositive responses.6 Key Point: Electrode placement affects ST segment slope and amplitude. The various placements do not result in comparable waveforms for analysis. For comparison of the resting 12-lead recording, arm and

6 Writing Group Exercise Standards 2291 FUNCTIONAL CL INICAL 02 COST BICYCLE TREADMILL PROTOCOLS CLASS STATUS MUKG/MIN METS ERGOMETER METS BALKE ELLESTAD USAWSAM SLOW MCHENRY STANFORD - WARE USAFSAM 6 KPDS 3 MIN % GRAD 32(3-2 OR 3 % % GRADE STAGES AT MIN MIN GRADE AT 1 WATT BRUCE 15) I I MPH %GR 313 MPH STAGES STAGES AT 2 MPH ~ -MN3MPH WI I I I FOR 70 KG STAGES S BODY WEIGHT MPH %GR NORMAL Z e 15 MPH %GR 16 AND O KPDS MPH %GR 24 MPH %GR 15 4I t S W z F 245? J E H~~~~140 DS IV _17_5 1_ FIGURE 3. Treadmill protocols with approximate oxygen uptakes. From Froelicher VF.: Exercise and Concepts. Chicago, Year Book Medical Publishers, Inc, 1987, p 15. Reproduced with permission. leg electrodes should be moved to the wrists and ankles, with the patient in the supine position. Multiple leads. Since a standard 12-lead ECG with electrodes placed on the limbs cannot be obtained during exercise, other electrode placements have been used. Differences can be minimized by placing the arm electrodes as close to the shoulders as possible, the leg electrodes below the umbilicus, and by recording the resting ECG with the patient supine. Any modification of lead placement should be recorded on the tracing. Relative sensitivity of leads. The lateral precordial leads (V4 through V6) are capable of detecting 90% of all ST depression observed in multiple lead systems. Other reports indicate that using other leads in addition to V5 will increase the yield of abnormal responses by about 10-25%. However, the specificity of an abnormal response in other leads is lower. A more extensive lead system is preferred in subsets of patients with a high prevalence of previous myocardial infarction or symptoms suggesting coronary artery spasm. ST depression in five leads or more usually predicts multivessel disease. A threelead system (V2, II, and V5) may be adequate for localizing ischemia related to spasm. This approach is also helpful for detection and identification of arrhythmias. Sometimes abnormalities may not be present or they may be seen as borderline in V5, whereas they are clearly abnormal in V4, V6, or other precordial leads. In asymptomatic individuals or those with nonspecific chest pain who have a normal resting ECG, recording a single lead such as CC5 may be adequate. Key Point: Complete 12-lead tracings during exercise are not needed in many individuals with normal resting ECGs. However, they are necessary in patients with arrhythmias, Q waves consistent with myocardial damage, or symptoms suggestive of corothe Heart: Clinical nary spasm, and when evaluating severity of disease in patients with known CAD. Recorders. There are many good recorders designed to capture high-quality ECG data during exercise. Many use microprocessors to generate average waveforms and make ECG measurements. The physician must compare the raw analog data with computer-generated output to validate its accuracy. Computer processing is not completely reliable because of software limitations in handling noise and inadequacy of the available algorithms. Equipment and protocols Figure 3 illustrates the relation of METs to stages in the common testing protocols. Numerous devices have been used to provide dynamic exercise for testing, including steps, escalators, and ladder mills. However, the cycle ergometer and treadmill are now the most commonly used dynamic exercise testing devices. Cycle. Mechanical or electrically braked cycles are calibrated in kiloponds (kpm) or watts and vary the force to the pedaling speed (rate-independent ergometers), permitting better power output control since it is common for uncooperative or fatigued patients to decrease their pedaling speed. The highest values of Vo2 and heart rate are obtained with pedaling speeds of rpm. One watt is equivalent to approximately 6 kpm. Since exercise on a cycle ergometer is nonweight bearing, kiloponds or watts can be converted to oxygen uptake in ml/min. METs are obtained by dividing Vo2 in ml/min by the product of body weight x 3.5. The cycle ergometer is usually less expensive, occupies less space, and makes less noise than a treadmill. Upper body motion is usually reduced, making it easier to obtain blood pressure measure-

7 2292 Special Report Circulation Vol 82, No 6, December 1990 ments and to record the ECG. Care must be taken to prevent isometric exercise of the arms. There is a marked difference between the body's response to acute exercise in the supine and erect positions. In healthy persons, stroke volume and end-diastolic volume change little during supine cycle exercise from volumes obtained at rest, whereas in the erect position, these values increase and then plateau during mild work. In patients with cardiac abnormalities, left ventricular filling pressure is more likely to increase during exercise in the supine position than in the erect position. When patients with angina perform identical submaximum cycle work in the supine and erect positions, heart rate is higher in the supine position, maximum work performed is lower in the supine position, and angina develops at a lower double product. ST segment depression is usually greater in the supine position because of the greater left ventricular volume. Treadmill. The treadmill should have front and side rails for patients to steady themselves; some patients may also require the assistance of the person administering the test. Patients should not tightly grasp the front or side rails since this decreases Vo2 and work and increases exercise time and muscle artifact. Most patients can walk without aid of hand rails, but older subjects may need such support. It is helpful if patients take their hands off the rails, close their fists, and place one finger on the rails to maintain balance after they are accustomed to walking on the treadmill. The treadmill should have both variable speed and grade capability and must be accurately calibrated. Protocols. Protocols for clinical exercise testing include an initial low load (warm-up), progressive uninterrupted exercise with an adequate duration in each level, and a recovery period. For cycle ergometry, the initial power output is usually 10 or 25 W (150 kpm/min), usually followed by increases of 25 W every 2 or 3 minutes until end points are reached. If arm ergometry is substituted for cycle ergometry, a similar protocol may be used, except that initial power output and incremental increases are lower. Two-minute stages are most popular with arm ergometry.7,8 Several different treadmill protocols are in use, the most popular of which is the Bruce. The advantages of the Bruce protocol include a seventh or final stage that cannot be completed by most individuals and its use in many published studies. Its disadvantages include large increments in work that make estimation of Vo2 max less accurate. The fourth stage can be either run or walked, resulting in different oxygen costs. Some patients are forced to stop exercising prematurely because of musculoskeletal difficulties or inability to tolerate the high work load increments. An initial zero and one half stages (1.7 mph at 0%, then 5% grade) can be used for limited patients. Many exercise testing laboratories currently use Balke-type protocols (i.e., Naughton [quite frequently used], Stanford, McHenry) with even MET levels for stage advances. The optimum protocol TABLE 6. Borg Scale for Rating Perceived Exertion 15-grade scale 10-grade scale 6 0 Nothing 7 Very, very light 0.5 Very, very weak (just noticeable) 8 1 Very weak 9 Very light 2 Weak (light) 10 3 Moderate 11 Fairly light 4 Somewhat strong 12 5 Strong (heavy) 13 Somewhat hard Very strong 15 Hard Very hard 10 Very, very strong (almost maximum) Very, very hard Maximum 20 From Pollock ML, Wilmore JH: Exercise in Health and Disease: Evaluation and Prescription for Prevention and Rehabilitation, ed 2. Philadelphia, WB Saunders Co, 1990, p 290. Reproduced with permission. should last 6-12 minutes and should be adjusted to the patient. Exercise protocols should be individualized according to the type of patient being tested. Threeminute stages are not necessary to achieve steady state at a low work load. Performance can be estimated with the oxygen cost of maximum work load or power output achieved rather than by total treadmill time if subjects do not use hand rails, allowing comparison of performance in different protocols. Key Point: It is important to adjust or select the treadmill or cycle ergometer protocol to the patient being tested. The optimum protocol is 6-12 minutes. Exercise capacity should be reported in METs rather than minutes. Submaximum versus maximum exercise testing In some cases, testing is terminated when the patient reaches 90% of predicted maximum heart rate for age and level of training. Unfortunately, there is a wide spread of maximum heart rate around the regression line, declining with age (SD = 12 beats/ min). Thus, the target heart rate is maximal for some subjects, beyond the limit of others, and submaximal for still others. A test is considered maximal when the patient appears to give a true maximum effort (point of bodily exhaustion) or when other clinical points are reached. Paradoxically, when using an age-predicted heart rate-targeted submaximum test, the most vulnerable patients are stressed to a relatively greater extent, whereas the less impaired are limited by the submaximum target heart rate. Perceived exertion. The subjective rating of the intensity of exertion perceived by the person exercising is a good indicator of relative fatigue. The con-

8 cept of perceived exertion has been used to subjectively quantify effort during exercise. Rather than using heart rate alone to clinically determine intensity of exercise, the 6 to 20 Borg scale of perceived exertion9 is useful (Table 6). Special verbal and written explanations about the rating of perceived exertion are available for patients. Although there is some variation among patients in their actual rating of fatigue, they seem to rate consistently from test to test. Thus, the Borg scale can assist the clinician in judging degree of fatigue reached from one test to another or to correlate the level of fatigue during testing with that experienced during daily activities. Indications for terninating exercise testing. Indications for interruption of an exercise test have been derived from clinical experience. Absolute indications * Drop in systolic blood pressure (persistently below baseline) despite an increase in work load * New onset of or increasing anginal chest pain * Central nervous system symptoms (ataxia, dizziness, or near syncope) * Signs of poor peripheral perfusion (cyanosis or pallor) * Serious arrhythmias (i.e., high-grade ventricular arrhythmias such as multiform complexes, triplets, and runs) * Technical difficulties monitoring the ECG or systolic blood pressure * Patient's request to stop Relative indications * ST or QRS changes such as excessive ST displacement, junctional depression, or marked axis shift * Increasing chest pain * Fatigue, shortness of breath, wheezing, leg cramps, or intermittent claudication * General appearance (see below) * Less serious arrhythmias, including supraventricular tachycardias * Development of bundle branch block that cannot be distinguished from ventricular tachycardia Postexercise period Some abnormal responses occur only in recovery after exercise. If maximum sensitivity is to be achieved with an exercise test, patients should be supine in the postexercise period; however, for patient comfort, many physicians prefer the sitting position. A cooldown walk after the test can delay or eliminate the appearance of ST segment depression; however, the cool-down may be indicated in some patients. Monitoring should continue for 6-8 minutes after exercise or until changes stabilize, with heart rate and ECG close to baseline. In the supine position, 4-5 minutes into recovery, approximately 85% of patients with abnormal responses are abnormal at this time only or in addition to any other time. An abnormal ECG response occurring only in the recovery period is not unusual. These responses will probably not be falsepositive unless they occur late in recovery. Mechanical dysfunction and electrophysiological abnormalities in Writing Group Exercise Standards 2293 the ischemic ventricle after exercise can persist from minutes to hours. Monitoring of blood pressure should continue during recovery. Interpretation Clinical responses Symptoms. Ischemic chest pain induced by the exercise test is strongly predictive of CAD and is even more predictive with ST depression. It is important to obtain a careful description of the pain from the patient to ascertain that it is typical angina rather than nonischemic chest pain. Silent ischemia (ST depression without pain) is associated with a better prognosis and milder CAD than ST depression with pain. Patient's appearance. The patient's general appearance is helpful in clinical assessment. A drop in skin temperature, cool and light perspiration, and peripheral cyanosis during exercise can indicate poor tissue perfusion due to inadequate cardiac output with secondary vasoconstriction. Such patients should not be encouraged to higher work loads. Neurological manifestations such as light-headedness or vertigo can also indicate inadequate cardiac output. Physical examination. Cardiac auscultation immediately after exercise can provide information about ventricular function. Gallop sounds or a precordial bulge can result from LV dysfunction. A mitral regurgitant murmur suggests papillary muscle dysfunction related to transitory ischemia. It is preferable to have patients lie supine after exercise testing and allow those who develop orthopnea to sit up. In addition, severe angina or ominous arrhythmias after exercise may be lessened by allowing the patient to sit up since ischemia may be decreased. Key Point: Symptoms and signs of ischemia induced by exercise testing are clinically important and their combinations influence interpretation. Exercise or functional capacity V 2 max is a measure of the functional limit of the cardiovascular system and the best index of exercise capacity. As previously discussed, Vo2 max is dependent on many factors (training, age, and gender) and is an indirect estimate of maximum cardiac output. A decline in maximum cardiac output is the major hemodynamic consequence of symptomatic CAD, causing a decrease in exercise capacity. Although many patients may stop exercising because of anginal pain, acute reduction in LV performance resulting in decreased stroke volume and increasing pulmonary artery pressure appear to be the mechanisms limiting cardiac output. A mean exercise capacity of 10 METs has been observed in nonathletic middle-aged healthy men. If patients with CAD reach 13 METs, their prognosis is good, regardless of other exercise test responses that may occur and medical or surgical treatment. In patients with an exercise capacity of less than 5 METs, mortality is higher than in those with higher exercise capacities. A normal exercise capacity does not exclude severe cardiac impairment. Mechanisms proposed to ex-

9 2294 Special Report Circulation Vol 82, No 6, December 1990 plain a normal work performance in these patients include increased peripheral oxygen extraction, preservation of systolic volume and chronotropic reserve, ability to tolerate elevated pulmonary wedge pressures without dyspnea, ventricular dilation, and increased levels of plasma norepinephrine at rest and during exercise. Many patients with decreased ejection fractions at rest can perform relatively normal levels of exercise, some without untoward effects, whereas others report increased fatigue for some time after the test. Key Point: An exercise capacity of 5 METs or less is associated with a poor prognosis in patients less than 65 years old. In the immediate postmyocardial infarction period, 5 METs is the usual exercise limit; 10 METs is considered an adequate level of training. In a patient with ischemia, 10 METs is associated with no improvement in survival with coronary artery bypass surgery (CABS) versus medical management. An exercise capacity of 13 METs indicates a good prognosis despite abnormal exercise test responses. Only well-trained aerobic athletes can achieve 20 METs (see Table 1). Ejection fraction does not necessarily predict exercise capacity. Hemodynamic Responses Blood pressure during exercise Blood pressure is dependent on cardiac output and peripheral resistance. Systolic blood pressure at maximum exertion or immediate cessation of exertion is considered a clinically useful first approximation of the heart's inotropic capacity. An inadequate rise or a fall in systolic blood pressure during exercise can occur. Although some normal subjects have a transient drop in systolic blood pressure at maximum exercise, this finding is frequently associated with severe CAD and ischemic dysfunction of the myocardium..exercise-induced hypotension also identifies patients at increased risk for ventricular fibrillation in the exercise laboratory. Key Point: A drop in systolic blood pressure below standing rest during exercise is associated with increased risk in patients with a prior myocardial infarction or myocardial ischemia. Heart rate during exercise Relatively rapid heart rate during submaximum exercise or recovery could be due to vasoregulatory asthenia, a condition decreasing vascular volume or peripheral resistance, prolonged bed rest, anemia, or metabolic disorders. This finding is relatively frequent soon after myocardial infarction and coronary artery surgery. Relatively low heart rate at any point during submaximum exercise could be due to exercise training, enhanced stroke volume, or drugs. The common use of 13-blockers, which lower heart rate, has complicated interpretation of heart rate response to exercise. Conditions that affect the sinus node can attenuate the normal response of heart rate during exercise testing. Key Point: Abnormalities of exercise capacity, systolic blood pressure, and heart rate response to exercise can be due to either left ventricular dysfunction or ischemia. Responses in subjects with normal resting electrocardiograms Normal responses. P wave. During exercise, P vectors become more vertical; P wave magnitude increases significantly in inferior leads. There are no significant changes in P wave duration. PR segment. The PR segment shortens and slopes downward in the inferior leads during exercise. The decreasing slope has been attributed to atrial repolarization (the Ta wave) and can cause false-positive ST depression in the inferior leads. QRS complex. The Q wave shows very small changes from the resting values; however, it does become slightly more negative at maximum exercise (avf). Changes in median R wave amplitude are noted near maximum effort. A sharp decrease in the R wave is observed in the lateral leads (V5) at maximum exercise and on into 1-minute recovery. In the lateral and vertical leads (V5 and avf), the S wave becomes greater in depth or more negative, showing a greater deflection at maximum exercise, and then gradually returning to resting values in recovery. As the R wave decreases in amplitude, the S wave increases in depth. J-junction depression. The J-junction is depressed in lateral leads to a maximum depression at maximum exercise, then gradually returns toward preexercise values in recovery. A dramatic increase in J-junctional depression is observed in all leads and is greatest at 1 minute into recovery. Subjects with resting J-junction elevation may develop an isoelectric J-junction with exercise; this is a normal finding. These changes return toward pretest values later in recovery. The normal ST segment vector response both to tachycardia and exercise is a shift rightward and upward. There appears to be considerable biological variation in the degree of this shift. T wave. A gradual decrease in T wave amplitude is observed in all leads during early exercise. At maximum exercise the T wave begins to increase, and at 1-minute recovery the amplitude is equivalent to resting values in the lateral leads. Abnormal responses. ST segment changes. The ST level is measured relative to the PR segment since the U-P segment disappears during exercise. ST elevation is measured as the deviation from the baseline ST level. ST depression is measured from the isoelectric PR level since the normal response is a downward shift from early repolarization. If the baseline ST segment is depressed, the deviation from that level to the level during exercise or recovery is considered. The current point for measuring the ST level is the J-junction. Points beyond this (60 or 80 msec) should only be used if the ST segment slope is horizontal or downsloping. Considering ST depression that is rapidly upsloping abnormal increases sensitivity but decreases specificity. Many ST areas or scores have been recommended, but none have been validated as superior to standard measurements.

10 Writing Group Exercise Standards 2295 hi on.c_ 'I '~C- IIt. A 0 2 my., AMPUTUDEAT SPSATIAL ST-T CLASSIC UPSLOPING TIME-NORMALZED STINDEX STTEGRAL MAGNITUDES ST6O STMIDPOINT FIGURE 4. Abnormal ST responses. From Froelicher VFJ: Exercise and the Heart: Clinical Concepts. Chicago, Year Book Medical Publishers, Inc, 1987, p 46. Reproduced with pernission. Exercise-induced myocardial ischemia can result in one of three ST segment manifestations on the surface ECG: depression, elevation, and normalization. ST segment depression. ST segment depression is the most common manifestation of exercise-induced myocardial ischemia. It is a global subendocardial ischemia, with direction determined largely by the placement of the heart in the chest. The standard criterion for this abnormal response is horizontal or downsloping ST segment depression of 0.10 mv or more for 80 msec. However, as shown in Figure 4, other criteria have been considered. Downsloping ST segment depression is a more serious condition than horizontal depression. In the presence of baseline abnormalities, exercise-induced ST segment depression is less specific for ischemia. Other factors related to the probability and severity of CAD include the amount, time of appearance, duration, and number of leads with ST segment depression. Severity of CAD is also related to the time of appearance of ischemic shifts. The lower the work load and double product at which it occurs, the worse the prognosis and the more likely the presence of multivessel disease. The persistence of ST depression in the recovery phase is also related to the severity of CAD. Key Point: The probability and severity of CAD are directly related to the amount of J-junction depression and are inversely related to the slope of ST segment (i.e., the greater the depression and the downslope, the more likely and more severe CAD). ST segment elevation. ST elevation must be classified by whether it occurs over Q waves of a myocardial infarction or in an ECG area without Q waves. The mechanisms and implications are significantly different. ST segment elevation has been more frequently observed in anterior leads (V1 and V2) with Q waves.10 ST segment elevation over Q waves of prior myocardial infarction. Prior myocardial infarction is the most frequent cause of ST segment elevation during exercise and appears to be related to the presence of dyskinetic areas or ventricular aneurysms. Approximately 50% of patients with anterior myocardial infarction and 15% of patients with inferior myocardial infarction exhibit this finding during exercise. Patients with elevation usually have a lower ejection fraction than those without elevation over Q waves. These changes can result in reciprocal ST depression simulating ischemia in other leads. ST segment elevation and depression during the same test may indicate multivessel CAD. The underlying extent of Q waves for the QRS duration actually determines the amount of ST elevation rather than independently reflecting the amount of dysfunction. ST segment elevation without Q waves. In patients without previous myocardial infarction (absence of Q waves on the resting ECG), ST segment elevation during exercise frequently pinpoints the site of severe transient ischemia resulting from significant proximal disease or spasm. Key Point: Severe transmural ischemia is the mechanism for ST segment elevation during exercise in patients without prior myocardial infarction or diagnostic Q waves on the resting ECG. It locates the site of ischemia in contrast to ST depression, which does not."l In patients with variant angina, ST segment elevation occurs during spontaneous anginal episodes, frequently at rest. During exercise, ST segment elevation has been reported in about 30% of these patients. A reversible thallium-201 perfusion defect usually corresponds to the site of ST elevation. Many patients with ST elevation have coexistent ST segment depression in other leads. Ventricular arrhythmias also appear to be more frequent in patients with ST elevation. ST segment normalization or absence of change. Another manifestation of ischemia may be normalization of or no change in the ST segment related to cancellation effects, but this is nonspecific. ECG abnormalities at rest, including T wave inversion and ST segment depression, reportedly return to normal during attacks of angina and during exercise in some patients with ischemic heart disease but can also be observed in subjects with a persistent juvenile pattern on the resting ECG. This cancellation effect is rare but should be considered. Cancellation is most likely

11 2296 Special Report Circulation Vol 82., o 6, December 1990 TABLE 7. Calculation of Sensitivity. Specificity, Relative Risk, and Predictive Value and Definition of Terms TP Sensitivity - TPFN_X1x TP+FN TP T+F TP+FP Relative Risk - FN TN+FN TN TP Specificity x 100 Predictive value of abnormal test = x 100 FP+TN TP+FP TP, true-positives or those with abnormal test and disease; FN, false-negatives or those with normal test and disease; TN, true-negatives or those with normal test and no disease; FP, false-positives or those with abnormal test and no disease. Predictive value of an abnormal response is the percentage of individuals with an abnormal test who are sick. Relative risk, or risk ratio, is the relative occurrence of a disease in the group with an abnormal test compared with those with a normal test. From Froelicher VF, Marcondes GD: Manual of Exercise Testing. St. Louis, Mosby-Yearbook, 1989, p 97. Reproduced with permission. in patients with severe CAD, yet they have the highest prevalence of abnormal tests. Diagnostic value of R wave changes. Substantial within-subject estimates of the variability of R wave amplitude changes during exercise in normal subjects have been reported. However, the average response in normal subjects is an increase in R wave amplitude during submaximum exercise, with a drop at maximum exercise. Exercise-induced changes in R wave amplitude have not improved diagnostic accuracy despite use of several lead systems, clinical subsets of patients, and different criteria for an abnormal response. Key Point: A multitude of factors affect the R wave amplitude response to exercise, and the response does not have diagnostic significance. T wave changes. In normal subjects, a gradual decrease in T wave amplitude is observed in all leads during early exercise. At maximum exercise the T wave begins to increase, and at 1-minute recovery amplitude is equivalent to resting values in lateral leads. U wave changes. U wave inversion is associated with LV hypertrophy, CAD, and aortic and mitral regurgitation. These conditions are associated with abnormal LV distensibility. Exercise-induced U wave inversion in patients with a normal resting ECG appears to be a marker of myocardial ischemia and suggests left anterior descending CAD. Other studies Exercise tests can be performed with radionuclear techniques to further evaluate myocardial perfusion and function. Thallium, an isotope that behaves like potassium, is taken up by perfused, viable myocardium when injected at maximum exercise. Imaging performed immediately after exercise can reveal defects. If these areas fill in 4 hours later, they are usually due to ischemia; if they do not fill in, the defects can be due to scarring or severe ischemia. Technetium can be tagged to red blood cells and can provide an image of the LV cavity blood volume during exercise. Changes in ejection fraction, wall motion, and ventricular volume can be assessed. Echocardiographic images and Doppler flow measurements can be made during and after exercise. Ejection fraction and wall motion can be assessed with this technique. Diagnostic Value of the Exercise Test Sensitivity and specificity Sensitivity and specificity are the terms used to define how effectively a test separates sick people from healthy individuals, that is, how well a test diagnoses disease. Sensitivity is the percentage of those with a disease who will have abnormal tests. Specificity is the percentage of those without the disease who will have normal test results and may be affected by drugs, baseline ECG patterns, and whether a test is submaximal or maximal. Sensitivity and specificity are inversely related; when sensitivity is the highest, specificity is lowest and vice versa. All tests have a range of inversely related sensitivities and specificities that can be selected by specifying a discriminant or diagnostic cut point. The choice of a discriminant value is further complicated by the fact that some exercise test responses do not have established values that separate normal subjects from those with disease. Once a discriminant value that determines a test's specificity and sensitivity is chosen, the population tested must be considered. If the population is skewed toward individuals with a greater severity of disease, the test will have a higher sensitivity. For instance, the exercise test has a higher sensitivity in individuals with triple-vessel disease than in those with single-vessel disease. A test can also have a lower specificity if it is used in individuals who are more likely to give false-positive results. For instance, the exercise test has a lower specificity in women and in individuals with mitral valve prolapse. Sensitivity and specificity of exercise-induced ST segment depression can be demonstrated by comparing the results of exercise testing and coronary angiography.12 From these studies, it can be seen that the exercise test cut point of 0.1 mv horizontal or

12 downsloping ST segment depression has approximately 84% specificity for angiographically significant CAD; that is, 84% of those without significant angiographic disease had a normal exercise test. These studies had a mean 66% sensitivity of exercise testing for significant angiographic CAD, with a range of 40% for one-vessel disease to 90% for three-vessel disease. Key Point: Sensitivity and specificity are inversely related, affected by the population tested, and determined by the choice of a cut point or discriminant value. Relative risk and predictive value Relative risk and predictive value are two other terms that help define the diagnostic value of a test. Table 7 shows how sensitivity, specificity, relative risk, and predictive value are calculated. Prognostic Use of the Exercise Test Rationale There are two principal reasons for estimating prognosis. The first is to provide accurate answers to a patient's questions about the probable outcome of his or her illness. Although discussion of prognosis is inherently delicate and probability statements can be misunderstood, most patients find this information useful in planning their work, recreational activities, personal estates, and finances. The second reason for determining prognosis is to identify patients in whom interventions might improve outcome. Pathophysiology of coronary artery disease The basic pathophysiological features of CAD include arrhythmic risk, myocardial damage (reflected by LV function), and the degree of myocardium in jeopardy. Arrhythmic risk does not appear to be independently predicted by exercise testing since the prognosis of arrhythmias is closely related to LV abnormalities. Exercise test responses due to myocardial ischemia include angina, ST segment depression, and ST segment elevation over ECG areas without Q waves. Predicting the amount of ischemia (i.e., the amount of myocardium in jeopardy) is difficult. It is inversely related to the double product at the onset of signs/symptoms of ischemia. Responses related to ischemia or LV dysfunction include chronotropic incompetence, systolic blood pressure drops, and poor exercise capacity. The only response specifically associated with LV dysfunction is ST elevation over Q waves, which carries an increased risk in patients with Q waves and indicates that they have lower LV function and possibly larger aneurysms as compared with those with Q waves without elevation. Exercise capacity correlates poorly with LV function in patients without signs or symptoms of heart failure. Exercise testing is not helpful in identifying patients with moderate LV dysfunction, which is part of the requirement for improved survival with surgery. LV dysfunction is better recognized by a history of heart failure, physical examination, resting ECG, TABLE 8. Writing Group Exercise Standards 2297 Purposes of Exercise Testing After Myocardial Infarction Predischarge submaximum test Setting safe exercise levels (exercise prescription) Optimizing discharge Altering medical therapy Triaging for intensity of follow-up Assuring, encouraging patient (first step in rehabilitation) Reassuring spouse Recognizing exercise-induced ischemia and arrhythmias Maximum test for return to normal activities Determining limitations (including exercise prescription) Prognostication Reassuring employers Determining levels of disability Triaging for invasive studies Selecting medications echocardiogram, or radionuclide ventriculogram. Several patient groups have been studied to determine prognosis with exercise testing, including postmyocardial infarction patients, patients with stable CAD (including silent ischemia), patients who became symptomatic after CABS, patients who had undergone percutaneous transluminal coronary angioplasty (PTCA), and asymptomatic individuals. Postmyocardial infarction patients. Purpose. Table 8 lists reasons for performing an exercise test in postmyocardial infarction patients. Exercise testing may expedite and optimize discharge from the hospital of patients recovering from a myocardial infarction. Ventricular arrhythmias not present at rest can be provoked during exercise. The patient's reaction to exercise, work capacity, and limiting factors at the time of discharge from the hospital can be assessed. An exercise test before discharge is important for providing guidelines for exercise at home, reassurance of physical status, and determination of risk of complications, and provides a safe basis for advising the patient to resume or increase his or her activity level and return to work. The test can demonstrate to the patient, family, and employer the effect of myocardial infarction on capacity for physical performance. Psychologically, it may improve self-confidence by decreasing the patient's anxiety about daily physical activities. The test also reassures spouses of patients' physical capabilities. The response to exercise testing reassures and encourages many patients to increase their activities. Some investigators use symptoms or sign-limited end points 2 or 3 weeks after myocardial infarction. However, a submaximum limited test seems more clinically appropriate. A heart rate limit of 140 beats/min and a MET level of 7 is arbitrarily used for patients under the age of 40; a heart rate limit of 130 beats/min and a MET level of 5 is used for patients over 40. A Borg perceived exertion level in the range of 13 to 15 can be used as a test end point, particu- A maximum larly for patients receiving pf-blockers.

13 2298 Special Report Circulation Vol 82, No 6, December 1990 test is probably more appropriate more than 3 weeks after myocardial infarction, when the patient is ready to resume full activities. Safety. A review of numerous patients with predischarge and postmyocardial infarction exercise tests reported few serious complications: two cases of recurrent myocardial infarction and two cases of ventricular fibrillation, one fatal. These findings represent 0.05% morbidity and 0.02% mortality.13 In studies of exercise testing after myocardial infarction with a follow-up for cardiac end points, tested patients were consistently at lower risk than those not tested, regardless of criteria used for testing.13 This finding supports the clinical judgment of the skilled clinician. Using the general criteria, only an abnormal systolic blood pressure response or a low exercise capacity were significantly associated with poor outcome. When the studies were subgrouped by whether testing was done before or after discharge from the hospital, a high proportion of predischarge test results indicated poor outcome. Risk predictors from exercise testing best identify patients who die soon after myocardial infarction, that is, before later testing. Submaximum testing resulted in the highest proportion of positive associations and the highest risk ratios. Abnormal responses at higher work loads are not as predictive as those at lower work loads.13 Key Point: In postmyocardial infarction patients, clinical judgment identifies patients at highest risk, and ST shifts are not as predictive as an abnormal systolic blood pressure response (early drop of 20 mm Hg or more or flat response for duration of the test) or poor exercise capacity. Exercise-induced ST segment depression appears to be associated with increased risk in patients without diagnostic Q waves.14 Patients with stable coronary artery disease. Studies using exercise testing of patients with stable CAD have attempted to predict angiographic findings, cardiac events in patients with silent ischemia, or improved survival with CABS. Angiographic findings. Numerous studies have tried to predict left main or triple-vessel disease or both.1' Different criteria have been used with varying results. Predictive value refers to the percentage of those with abnormal criteria who actually have left main or triple-vessel disease. Exertional hypotension. In most studies, exerciseinduced hypotension predicts a poor prognosis, with a positive predictive value of 50% for left main/triplevessel disease.16 Exercise-induced hypotension is also associated with cardiac complications during exercise testing, appears to be alleviated by CABS, and can occur in patients with CAD, valvular heart disease, or cardiomyopathy. Occasionally, patients without clinically significant heart disease will exhibit exerciseinduced hypotension during exercise related to antihypertensive therapy or prolonged strenuous exercise. Key Point: The definition of exercise-induced hypotension is of crucial importance in evaluation of the exercise test response. A drop in systolic blood pressure below preexercise values is the most ominous criterion; a drop of 20 mm Hg or more without a fall below preexercise values has little, if any, predictive value. Exercise-induced hypotension can be related to either LV dysfunction (as reflected by myocardial infarction status) or ischemia. Exerciseinduced hypotension that is not associated with either of these factors appears to be benign. Cardiac events in patients with silent ischemia. In the presence of unstable angina, asymptomatic (silent) ischemia detected by ambulatory ECG (Holter) recording appears to confer an adverse prognosis. The prognostic implication of asymptomatic ischemia detected during exercise testing is controversial. It has been suggested that those with silent ischemia are at greater risk for cardiac death because they do not have an intact warning system. However, in three large population studies of patients with a high prevalence of CAD who underwent exercise testing, those with ST segment depression with or without angina during testing had similar prognoses.17 Ischemia is silent in approximately 60% of patients with ischemic ST segment depression. Silent ischemia occurring with treadmill testing does not confer an increased risk for death relative to patients experiencing angina. Thus, therapy should not be more intense for silent ischemia than for patients with angina and ST depression. Controversy continues about the importance of silent ischemia as assessed by ambulatory recording compared with treadmill testing. Some studies suggest that only patients with abnormal exercise tests at low work loads have significant amounts of silent ischemia on ambulatory recording. Exercise-induced ventricular arrhythmias. In patients with CAD, exercise-induced ventricular arrhythmias do not usually represent an independent risk factor for subsequent mortality or coronary events. However, recent data suggest that these arrhythmias add independent prognostic information to thallium-201, ST segment, and heart rate changes,18'19 and they are associated with severe CAD and wall motion abnormalities. Exercise testing may be of considerable value in evaluation of drug therapy of ventricular arrhythmias, particularly in subjects with CAD. Improved survival after coronary artery bypass surgery. One study suggests that patients with cardiomegaly, exercise capacity of less than 5 METs, or a maximum systolic blood pressure of less than 130 mm Hg would have a better outcome if treated with surgery.20 In one surgery trial, patients who had an exercise test response of 1.5 mm of ST segment depression showed enhanced survival with surgery. Improved survival also extended to those with baseline ST segment depression and those with claudication.2' In another trial,22 the surgical benefit to mortality was greatest in patients with 1 mm ST segment depression at less than 5 METs. There was no difference in mortality in patients who exceeded exercise capacity of 10 METs.

14 Key Point: In patients with stable CAD, studies comparing angiographic findings, cardiac events, and the differential outcome of CABS compared with medical therapy have shown the exercise test to have prognostic power. These studies indicate that patients with marked degrees of ST segment depression (i.e., greater than 2 mm, in multiple leads, and prolonged into recovery) accompanied by poor exercise capacity, exertional hypotension, premature ventricular contractions, angina, or all of the above are at increased risk of having triple-vessel or left main disease and a poor prognosis. Patients who become symptomatic after coronary artery bypass surgery. Predicting prognosis of patients who become symptomatic after CABS is an important issue. Each year, more than 300,000 Americans undergo this procedure. Several studies have evaluated graft occlusion and recurrence of symptoms; however, exercise-induced ST depression does not predict prognosis after CABS. An exercise capacity of 9 METs or more indicates a good prognosis, regardless of other responses.23 Patients who have undergone percutaneous transluminal coronary angioplasty. Exercise testing may be of value in the routine (6-12 month) follow-up of patients who have undergone PTCA, especially in the evaluation of chest pain and detection of restenosis. Testing is of particular benefit in the cardiac rehabilitative setting and may be more helpful in the patient with suggestive symptoms of ischemia or the patient whose progress in rehabilitation is limited. Apparently healthy individuals. Silent ischemia induced by exercise testing in apparently healthy men is not as predictive of a poor outcome as once thought. Use of the exercise test for screening is even more misleading than previously appreciated because of the higher false-positive rate. Approximately 19 of 20 abnormal ST responses will be false-positives. Earlier superior results can be explained by inclusion of angina pectoris as an end point, which could be caused by cardiac concerns resulting from an abnormal exercise test.24,25 Key Point: The nonselective use of exercise testing for screening apparently healthy individuals should be discouraged because of the poor predictive value of minimum (1 mm) ST segment depression. Unfortunately, this abnormal response may lead to psychological and vocational disability as well as unnecessary medical expense and risk. In these individuals, the test is helpful for motivational purposes and for setting exercise prescriptions. Only combinations of other abnormal responses and 2 mm ST depression should be considered predictors of increased risk of cardiovascular events in asymptomatic men. There is substantial evidence to support the use of exercise testing as the first noninvasive step after the history, physical examination, and resting ECG in prognostic evaluation of patients with CAD. Exercise testing accomplishes both purposes of prognostic testing: it provides information about the patient's status and is helpful when making recommendations for Writing Group Exercise Standards 2299 optimum management. Some studies show that the value of exercise testing for risk stratification is enhanced by the addition of radionuclide imaging, particularly with submaximum testing after an uncomplicated myocardial infarction. Exercise test results enhance selection of patients who should undergo further evaluation such as coronary angiography. Since the exercise test can be performed in the physician's office and provides valuable information about activity levels, response to therapy, and disability, the exercise test is the reasonable first choice for prognostic assessment. Because of its widespread use, the exercise test can have an enormous impact on cost-effective delivery of cardiovascular care. Other Uses of the Exercise Test Assessment of valvular heart disease Exercise testing has been used in patients with valvular heart disease to quantify disability, to reproduce exercise-induced symptoms, and to evaluate response to medical and surgical intervention.26 The exercise test has also been used to identify concurrent CAD, but there is a high prevalence of false-positive responses (ST depression not due to ischemia) because of frequent baseline ECG abnormalities and LV hypertrophy. Some physicians use exercise testing to determine when surgery is indicated. Exercise testing has been used most frequently in patients with aortic stenosis. Aortic stenosis. Effort syncope in patients with aortic stenosis27,28 is an important and well-appreciated symptom. Most guidelines for exercise testing list moderate to severe aortic stenosis as a contraindication for testing because of concern about syncope and cardiac arrest. Therefore, exercise testing of patients with aortic stenosis should be restricted to subjects with mild to moderate gradients. Four proposed mechanisms for exercise-induced syncope in patients with aortic stenosis include carotid hyperactivity, LV failure, arrhythmia, and LV baroreceptor stimulation. Exercise testing is relatively safe in both the pediatric and adult patient when performed appropriately. Attention should focus on the patient's symptoms, minute-by-minute response of blood pressure, slowing heart rate, and ventricular and atrial arrhythmias. In the presence of an abnormal blood pressure response, the patient with aortic stenosis should take at least a 2-minute cool-down walk at a lower stage of exertion to avoid acute LV volume overload, which may occur when the patient lies down. Exercise plays an important role in the objective assessment of symptoms, hemodynamic response, and functional capacity. Whether ST segment depression indicates significant CAD remains unclear. Benefits of surgery and baseline impairment can be quantified by performing an exercise test before and after the operation. Exercise testing offers the opportunity to objectively evaluate disparities between history and clinical findings, as, for example, in the elderlv asymptomatic subject with physical and/or

15 2300 Special Report Circulation Vol 82, No 6, December 1990 Doppler findings of severe aortic stenosis. Echocardiographic studies are often inadequate in such patients, particularly in smokers. When Doppler echocardiography reveals a significant gradient in the asymptomatic patient with normal exercise capacity, progress should be monitored until symptoms develop. Surgery appears to be indicated in patients with an inadequate systolic blood pressure response to exercise or a fall in systolic blood pressure from the resting value when symptoms occur. Aortic regurgitation. Patients with aortic regurgitation29 usually maintain a normal exercise capacity for a longer time than those with aortic stenosis. Volume work load of the myocardium requires less oxygen than pressure work. During exercise, there is a decrease in diastolic duration and regurgitation volume favoring forward output. As the myocardium fails, heart rate tends to slow and ejection fraction and stroke volume decrease. There is an increase in ventricular diameter and metabolic requirements. Exercise testing is useful for monitoring patients with aortic regurgitation, using appearance of ST segment depression, a reduction of heart rate response to each work load, and decrease in Vo? max as markers for worsening LV function. Mitral stenosis. Patients with mitral stenosis30 may show either a normal or excessive increase in heart rate during exercise. Since stroke volume cannot be increased, the normal rise of cardiac output is attenuated and may eventually fall during exercise, frequently accompanied by exercise-induced hypotension. A rise in pulmonary resistance results in increases in myocardial oxygen demands. In patients with mitral stenosis, chest pain and ST segment depression during exercise may occur as a consequence of reduction in coronary perfusion or because of pulmonary hypertension. ST depression is attributed to a decrease in coronary perfusion as a consequence of a fall in cardiac output and increased myocardial oxygen demand owing to right ventricular overload. Shortening of diastole associated with tachycardia and increased pulmonary blood flow during exercise increases preexistent mitral stenosis and may cause pulmonary congestion. Mitral regurgitation. Patients with mild to moderate mitral regurgitation31 maintain normal cardiac output during exercise. Blood pressure, heart rate, and ECG responses are usually normal. When mitral regurgitation occurs suddenly during exercise as a result of ischemic papillary muscle dysfunction, a flat response in systolic blood pressure can occur. Patients with severe mitral regurgitation usually show a decreased cardiac output and limited exercise capacity. ST segment depression is infrequent in these patients since there is no significant increase in myocardial oxygen consumption with mitral regurgitation. However, a hypotensive response can develop and arrhythmias frequently occur. Mitral valve prolapse. Several mechanisms have been suggested to explain ST depression in patients with mitral valve prolapse,32 including regional ischemia of the papillary muscle, abnormalities of the coronary arteries, compression of the anterior descending artery, coronary spasm, and primary cardiomyopathy. Angiography and scintigraphy studies in these patients have been normal. ECG changes can be normalized by propranolol or other nonselective,3-blockers, improving the specificity of the exercise test. Evaluation of an exercise program An exercise test is often used to evaluate the safety of an exercise training program and is useful in formulating an exercise prescription. In general, a sedentary individual who at the age of 40 decides to enter an exercise program of a higher intensity than walking at 50-60% of maximum heart rate reserve should undergo an exercise test. Testing should also be recommended for younger individuals with risk factors or a strong family history of CAD. Rather than give a predicted value, because of the wide scatter of maximum heart rate when plotted against age, it is better to determine an individual's maximum heart rate to assign a target for training. It is advantageous in certain individuals to objectively evaluate the response to exercise in a monitored situation before an exercise program is begun. An exercise test can be used in adult exercise or cardiac rehabilitation programs to safely advance an individual to a higher intensity. Improvement in exercise capacity as demonstrated by an exercise test can also be an effective incentive to continue the program and encourage risk factor modification. (Further information may be found in the section titled "Exercise Training.") Functional classification of disability Exercise testing is used to determine the degree of disability of patients with various forms of heart disease. Patients who exaggerate their symptoms or who have a psychological impairment can often be identified. Exercise testing is a more accurate measure of the degree of cardiac impairment than a physician's assessment of exercise capacity. Vo2 max, either directly measured or estimated, is the best noninvasive measurement of the exercise capacity of the cardiovascular system. Inability to reach 5 METs (below 18 ml. kg` min-1) without signs or symptoms is a criterion of disability used by the Social Security administration. Determination of a patient's exercise capacity affords an objective measurement of the degree of cardiac impairment and can be useful in treatment.33 Evaluation of risk for surgery Results of exercise testing do not appear to substantially add to the risk stratification provided by the resting ECG in patients without known CAD who are candidates for major elective noncardiac surgery.34 Therefore, exercise testing is not recommended as a routine procedure before major elective noncardiac surgery under general anesthesia. Exercise testing has been used in patients with intermittent claudication to evaluate results of iliofemoral bypass.

16 Evaluation ofpatients before and after revascularization Efficacy of an intervention can be noninvasively assessed by exercise testing since signs and symptoms of ischemia can be demonstrated and exercise capacity can be measured.35 Drugs and Exercise Testing 13-Blockers Patients with angina who receive fl-blockers may achieve a higher exercise capacity with less ST segment depression and less angina if the drugs prevent their reaching the ischemic double product. However, angina disappears in some individuals but ST depression increases if the ischemic double product can still be reached. Maximum heart rate and systolic blood pressure product may be profoundly reduced. These agents have also been used to normalize ST segment depression in patients with vasoregulatory abnormalities and mitral valve prolapse. The time of ingesting medications before testing should be recorded. Vasodilators These agents can increase exercise capacity in patients with angina or heart failure or both.36 Problems with assessing long-acting nitrates include the single-dose effect versus tolerance resulting from chronic administration. Tolerance seems to develop sooner in patients with angina than in those with chronic heart failure. There has been no scientific validation that long-acting nitrates increase exercise capacity in patients with angina when they are tested after chronic administration. Hydralazine decreases peripheral resistance and arterial blood pressure. There is an increase in heart rate (reflex tachycardia), which tends to increase cardiac output. This agent is useful in treatment of heart failure by decreasing afterload and increasing exercise capacity. Angiotensin-converting enzyme inhibitors These agents decrease blood pressure at rest and during exercise through decreases in plasma levels of angiotensin II and aldosterone. They increase exercise capacity in patients with chronic heart failure and enhance their survival rates. Calcium antagonists Calcium antagonists (slow channel-blocking agents) have multiple hemodynamic effects. They can delay time to ischemia and improve exercise capacity. ST segment depression is usually delayed until higher work loads. Heart rate and systolic blood pressure are decreased for a given level of exercise. Digitalis ST segment depression can be induced or accentuated during exercise in individuals who are taking digitalis, including both normal subjects and patients with CAD.37 Profound ST segment depression almost always indicates ischemia, even in patients who are taking digitalis. A normal QT interval is associated with digitalis-induced ST changes, while prolonged QT intervals occur with ischemia. Exercise-induced ST segment depression is said to persist for 2 weeks after digoxin is discontinued. Writing Group Exercise Standards 2301 Antiarrhythmic agents Quinidine can cause prolongation of phase 2 of the ventricular action potential, decreasing the repolarization gradient during the ST segment and thus diminishing the magnitude of ST depression. However, quinidine does not change the ST segment, heart rate, or Vo2 max in normal subjects or patients with CAD. A decrease of 20 beats/min in maximum exercise heart rate has been reported in patients taking amiodarone. Amiodarone also increases duration of the QRS complex during exercise. Diuretics Most diuretics have little influence on heart rate and cardiac performance but decrease plasma volume, peripheral resistance, and blood pressure. Diuretics can cause hypokalemia, producing muscle fatigue, ventricular ectopy, and, rarely, ST segment depression. Special Cases of Exercise Testing Interpretation Exercise testing in women The difference in predictive accuracy of exercise testing between men and women can be explained in part by the difference in prevalence of CAD.38 However, specificity is also intrinsically lower in women. Therefore, it is important to remember the following: 1) Careful characterization of chest pain is especially significant, 2) ST segment depression in the presence of typical angina is highly predictive of disease, compared with those with atypical or no pain, and 3) decrease in maximum systolic blood pressure during exercise is usually not related to heart disease in women. Several mechanisms have been suggested to explain the high false-positive rate of ST depression in women, including medications (digitalis) and resting ST-T abnormalities. Because estrogens have a similar chemical structure to digitalis, they may be at least partially responsible for the high prevalence of false-positive exercise test results in women. Hypertension Exercise testing has been proposed as a means of detecting labile hypertensives or individuals who will eventually become hypertensive, but there is a lack of support for this theory.39'40 Hypertensives frequently have ECG abnormalities (LV hypertrophy with strain) and myocardial hypertrophy, which both make false-positive ST responses more likely. Cardiomyopathies Exercise testing has been used in patients with dilated cardiomyopathy to determine exercise capacity, assess pulmonary response to LV dysfunction, determine the grade of ventricular ectopy, and evaluate the effectiveness of treatment.41 Patients with LV dysfunction usually have reduced exercise capacity and develop signs and symptoms of pulmonary and right ventricular involvement. There is an inadequate increase in cardiac output during exercise, which limits Vo2 max and exercise tolerance. Patients with severe LV dysfunction can often double cardiac output only with upright exercise. Stroke volume may increase normally during upright exercise despite a decrease in LV ejection fraction. Ventricular dilation

17 2302 Special Report Circulation Vol 82, No 6, December 1990 facilitates use of the Starling mechanism but may reduce chronotropic reserve. With increasing exercise, stroke volume and cardiac output cannot continue to meet the increased demands. Exertional hypotension is often observed. Certain patients may have normal exercise tolerance despite severe LV dysfunction. Several compensatory mechanisms have been proposed to explain the poor correlation between LV function and exercise capacity. This is especially so for those with a resistance to right-sided impairment (i.e., pulmonary congestion). Exercise may increase the frequency of premature ventricular contractions or induce other more serious arrhythmias. Even supraventricular arrhythmias can lead to ventricular tachycardia. Hypertrophic cardiomyopathy Exercise can be related to sudden death due to arrhythmias in this condition.42'43 Chest pain, an abnormal resting ECG, and exercise-induced ST segment depression are frequent. In this condition, exercise testing (under careful supervision) is especially helpful to demonstrate the level at which significant events occur, such as the presence or severity of arrhythmias, myocardial ischemia, murmurs indicating obstruction in LV outflow, and presyncopal manifestations. Ventricular arrhythmias are often observed during exercise. Intracardiac blocks Intraventricular blocks. Intracardiac blocks can exist before exercise or develop or disappear during exercise. Rate-dependent intraventricular blocks that take place during exercise often precede the appearance of chronic blocks present at rest Diagnosis of ischemia from the exercise ECG is impossible when left bundle branch block is present. There can be a marked degree of ST segment depression in addition to that found at rest in normal subjects with left bundle branch block. There is no difference in ST segment response to exercise between those with and those without ischemia. Left bundle branch block that occurs with heart rate below 125 beats/min in patients with typical angina is frequently associated with CAD, whereas left bundle branch block occurring at a heart rate above 125 beats/min occurs more frequently with normal coronary arteries. The presence of intraventricular blocks and their disappearance during exercise are rare. Patients with left bundle branch block who develop a normal QRS pattern during exercise have been reported. Right bundle branch block. Preexisting right bundle branch block47-51 does not influence interpretation of the exercise test except in the anterior precordial leads, where ST depression is frequent. However, sensitivity of exercise testing in these patients is uncertain. Exercise-induced ST segment depression in inferior and lateral leads in subjects with preexisting right bundle branch block without significant CAD is not anticipated. Intraventricular blocks during exercise. In addition to left or right bundle branch block, left anterior or posterior hemiblock and bifascicular block (a combination of right bundle branch block and left anterior or posterior hemiblock) may be induced by exercise. The presence of such blocks is primarily a rate-related phenomenon occurring during exercise as the sinus rate increases beyond a critical point. Intraventricular blocks are difficult to distinguish from ventricular tachycardia. Conduction abnormalities. Atrioventricular conduction disturbance. Shortening of the PR interval (as much as 0.10 or 0.11 second) during exercise as the sinus rate increases is common, probably because of increased sympathetic tone, and usually occurs in young, healthy individuals. First-degree atrioventricular block. First-degree atrioventricular (AV) block occurs occasionally at the end of exercise or during the recovery phase. Medications or conditions that may produce prolonged AV conduction time (e.g., digitalis, propranolol, myocarditis) predispose the individual to lengthening of the PR interval. Second-degree atrioventricular block. The occurrence of Wenckebach Mobitz type I AV block during exercise is rare. The clinical significance of exerciseinduced Mobitz II AV block is not known but may also be a rate-related phenomenon, appearing as the sinus rate is accelerated beyond a critical level. Complete atrioventricular block. Acquired complete AV block at rest may be a relative contraindication to exercise testing. Exercise testing can be conducted in patients with congenital complete AV block, provided there are no coexisting significant congenital anomalies. Sinus arrest. Rarely, patients develop long periods of sinus arrest immediately after exercise. Sinus arrest usually occurs in patients with severe ischemic heart disease. Preexitation syndromes. Exercise may provoke, abolish, or not interfere with anomalous AV conduction in individuals with known Wolff-Parkinson- White syndrome (WPW).52 Exercise usually does not abolish anomalous AV conduction, but when it does, these individuals are thought to be in less danger of exercise-induced ventricular tachycardia. When exercise does not interfere with preexisting anomalous AV conduction, significant ST depression can be observed during exercise testing. In the presence of WPW syndrome, the ST depression may not be due to ischemia but may instead be a false-positive occurrence. There is a low prevalence of tachyarrhythmias during or after exercise in WPW patients, although exercise has been considered a predisposing factor to initiate the tachyarrhythmia in this syndrome. Approximately half of WPW patients develop normal conduction during the test. Cardiac arrhythmias Exercise may induce cardiac arrhythmias under several conditions, including diuretic and digitalis therapy,53-55 and recent ingestion of alcohol or caffeine may exacerbate arrhythmias. Since exercise increases myocardial oxygen demand, in the presence of CAD myocardial ischemia could predispose the

18 patient to ectopic activity during exercise. It appears that subendocardial ischemia (ST depression) is not as arrhythmogenic as transmural ischemia (ST elevation). Exercise-induced arrhythmias are generated by enhanced sympathetic tone, increased myocardial oxygen demand, or both. The immediate postexercise period is particularly dangerous because of high catecholamine levels that are associated with a generalized vasodilation. Peripheral arteriolar dilation induced by exercise and reduced cardiac output resulting from diminished venous return secondary to sudden termination of muscular activity may lead to a reduction in coronary perfusion while heart rate is elevated. The increased sympathetic tone in the myocardium may stimulate ectopic Purkinje pacemaker activity by accelerating phase 4 of the action potential, provoking spontaneous discharge and leading to increased automaticity. Exercise can suppress cardiac arrhythmias present at rest. This phenomenon has been attributed to the overdrive suppression of the ectopic impulse formation by sinus tachycardia induced by exercise-vagal withdrawal and increased sympathetic stimulation. It has also been suggested that exercise-induced sinus tachycardia may inhibit automaticity of an ectopic focus because it reduces automaticity of the Purkinje tissue. Premature ventricular contractions are the most frequent cardiac arrhythmia during exercise, followed by supraventricular arrhythmias and fusion beats. Their prevalence is directly related to age and cardiac abnormalities. In general, premature ventricular contractions are of concern in patients with a family history of sudden death or a personal history of cardiomyopathy, valvular heart disease, or severe ischemia. A subgroup of patients without CAD and no LV dysfunction have sustained ventricular tachycardia, which is often produced by exercise testing. Isoproterenol infusion may induce this arrhythmia and verapamil may prevent it. Sinus arrhythmias with periods of sinus bradycardia and wandering atrial pacemaker are relatively common during exercise and the immediate recovery phase. Atrial premature contractions and atrial group beats can occur in either normal or diseased hearts. Exercise-induced transient atrial fibrillation and flutter occur in less than 1% of individuals who undergo exercise testing.56 These arrhythmias may be induced by exercise in healthy individuals or patients with rheumatic heart disease, hyperthyroidism, WPW syndrome, or cardiomyopathy. Paroxysmal AV junctional tachycardia is observed during exercise only rarely. Exercise-induced supraventricular arrhythmias alone are not related to CAD but are more often related to pulmonary disease, recent alcohol ingestion, or excessive caffeine. Writing Group Exercise Standards 2303 Informed Consent for Exercise Testing To determine my cardiovascular response to exercise, I voluntarily agree to engage in an exercise test. The information obtained about my heart and circulation will be used to help my doctor advise me about activities in which I may engage. I have been told that before I undergo the test, I will be interviewed and examined by a physician in an attempt to determine if I have a condition indicating that I should not engage in this test. I am told that the test I will undergo will be performed (description), on with a gradually increasing effort until symptoms such as fatigue, shortness of breath, or chest discomfort may appear, indicating to me that I should stop. I have been told certain changes may occur during the test, including abnormal blood pressure, fainting, abnormal ECG showing heart "strain," disorders of heart beat (too rapid, too low, or ineffective), and, possibly, heart attack and death. I agree that the information obtained may be used and published for statistical or scientific purposes. I have read the above and understand it, and my questions have been answered to my satisfaction. Patient Physician supervising the test Witness Date Exercise Training For individuals beginning training, care must be taken to ensure that apparently healthy individuals do not have detectable disease and that patients are stable with no evidence of new or changing symptoms. Exercise testing is the most useful tool to establish guidelines for exercise training in apparently healthy adults and is mandatory for patients with known or suspected cardiovascular disease. Care should be taken to exclude patients with evidence of uncontrolled heart failure or arrhythmia. Medical clearance should be obtained for most adults before entry into exercise training programs. Training programs for patients with cardiovascular disease should be medically supervised until low risk of activity has been established. Medical coverage must be immediately available in exercise training programs involving patients with heart disease, and a responsible physician should be designated. Physician presence is discussed under the section titled "Medically Supervised Group." Exercise Training ofapparently Healthy Individuals Risks of exercise Exercise has both risks and benefits, and the challenge to the physician is to provide guidelines that minimize risks and maximize benefits. Screening procedures are not perfect for identifying the rare individual who is at risk, but risks can be decreased by proper screening and precautions. Many factors affect risk of exercise. Three of the most important are age, presence of heart disease,

19 2304 Special Report Circulation Vol 82, No 6, December 1990 TABLE 9. Risk of Sudden Cardiac Arrest During Exercise Training Sudden cardiac arrests Study Status Activity Monitoring Supervision events/hr In the general population Vuori et a157 normal cross-country skiing none none 1/600,000 Gibbons et a158 normal jogging none none 1/375,000 swimming tennis Thompson et al59 normal jogging none none 1/396,000 Vander50 normal jogging none none 1/888,000 court games Average for general population 1/565,000 Individuals with known heart disease Fletcher and Cantwell6' cardiac jogging intermittent present 1/6,000 Leach et a162 cardiac jogging intermittent 1/12,000 Mead et a163 cardiac jogging intermittent present 1/6,000 Hartley64 cardiac jogging intermittent present 1/6,000 Hossack and Hartwig65 cardiac jogging none present 1/65,185 Haskell66 cardiac mixed intermittent present 1/22,028 Van Camp and Peterson67 cardiac mixed continuous present 1/117,333 Hartley* cardiac mixed continuous present 1198,717 Van Camp* cardiac mixed intermittent present 1/121,955 Hartley* cardiac bicycling intermittent none 1/70,000 walking Fletcher* cardiac mixed intermittent present 0/70,200 Average all cardiac 1/59,142 *Unpublished data. and intensity of exercise. Sudden cardiac death is rare in normal individuals. In individuals under the age of 35, sudden cardiac death is usually attributed to congenital heart disease, whereas CAD is a more likely cause for those over 35. The results of selected studies reporting risks of sudden cardiac arrest during exercise training are summarized in Table 9. These studies indicate that in the general population, risk of sudden cardiac death during vigorous exercise is very low. Since these studies were not randomized controlled trials, the contribution of each potential variable to incidence of sudden cardiac arrest or death cannot be determined. Based on these data, it is believed that the benefits of exercise exceed the risks, and individuals should be encouraged to exercise, provided they take measures to minimize risk. It is recommended that anyone who plans to begin an exercise program more vigorous than walking should have a current (within 2 years) physical examination. Individuals under age 40 who have a normal physical examination, no symptoms of cardiovascular disease, no major coronary risk factors, and no physical findings (including murmurs and hypertension) can be considered free of disease, do not need an exercise test, and should not be restricted in their exercise program. Individuals 40 years of age or older or those with abnormal physical examinations (murmurs, etc.) or two or more major coronary risk factors have a higher prevalence of occult heart disease than their younger counterparts. If these individuals wish to participate in vigorous exercise (such as jogging or running), a symptom-limited, maximum exercise test should be performed to ensure that there are no signs of occult heart disease. If their health status is uncertain, these individuals should restrict their activities to moderate intensities. Key Point: The risks of serious complications of physical activity are highest during vigorous exercise and in individuals with heart disease. Hence, screening should ensure that cardiovascular disease is not present or that physical activity is limited to moderate intensities (walking or the equivalent) or is medically supervised. Physiological Changes Physical conditioning is measured as Vo2 max exercise test time, submaximum heart rate response, or ability to perform a standard amount of exercise. Certain physiological adjustments occur with training and are associated with improved functional capacity. Maximum oxygen uptake. Vo2 ma is the peak oxygen uptake achieved by muscular exercise. By strictest definition, Vo2 max cannot be exceeded despite an increase in power output. Although demonstration of the Vo2 plateau against work load is certainly a valid demonstration of Vo2 max patients often cannot achieve the plateau because of leg fatigue, lack of necessary motivation, and discomfort. Hence, it is

20 lu 0 cc Q.,, fcorw training 0 Aftir training O Mairmal Ix.zwit OXYGEN UPTAKE, I/min FIGURE 5. Mean values for stroke volume and heart rate in 15 middle-aged subjects at rest (prone and upright position) and during submaximum and maximum exercise in upright position before and after physical conditioning. From Hartley et al. 68(p341) Reproduced with permission. customary to refer to Vo2 max as the peak Vo2 during volitional maximum exercise. In clinical practice, Vo2 max is not usually measured during an exercise tolerance test but estimated from peak work intensity achieved. Data presenting VO2 max equivalents for exercise test work stages is presented in Figure 3. Increased Vo2 max after training is associated with an increase in the capacity of the cardiovascular system to deliver oxygen and of the muscles to use that oxygen (greater avo2 difference and use). Higher cardiac output is achieved solely by an increase in stroke volume since maximum heart rate is not usually increased after training in normal individuals.68 Vo2 is the product of cardiac output and systemic avo2 difference; the maximum value increases by adjustment of both of these components. Some of the increase is the result of widening of the avo2 difference as well as an increase in cardiac output.68 Key Point: The increase in V02 max as a result of training normal individuals is due to a higher maximum cardiac output and to greater extraction of oxygen from the systemic circulation, reflecting both central and peripheral adjustments. Central hemodynamic changes...i j cr.. Although a higher maximum cardiac output can be achieved after training, submaximum values are usually unchanged.69 Submaximum heart rate is reduced after training, with a concomitant increase in stroke volume.6869 t Writing Group Exercise Standards 2305 The mechanism of these changes is not known. Exercise training has resulted in an increase in myocardial contractility in animals.70 In humans, contractility has not consistently been shown to increase. An increase in stroke volume, which occurs with short-term training, is probably largely related to augmentation of blood volume.71 Figure 5 depicts relations of heart rate and stroke volume before and after training. Key Point: Submaximum heart rate is reduced after training in normal individuals, but stroke volume is increased so that cardiac output is unchanged. Autonomic nervous system changes. Blood and urinary catecholamine levels are lower at rest and during submaximum exercise after training,72 presumably because of less sympathetic nervous system activity. Such changes are not likely with maximum exercise. Parasympathetic tone may also be increased and, with sympathetic adjustments, may account for the slower heart rate and lower arterial blood pressures seen after training. Peripheral changes. Skeletal muscle changes after exercise training include increase in oxidative enzyme concentration, increase in capillary density, increase in myoglobin concentration, adaptation of muscle fiber type to higher percentage of red (slow twitch) fibers, and increase in muscle glycogen. All potentially contribute to greater capacity to use oxygen.73 Key Point: Greater oxidative potential in the skeletal muscles after training probably contributes to higher Vo2 max. Submaximum endurance capacity. Endurance training enhances ability to perform exercise at submaximum intensities,74 as demonstrated by either exercising longer at a similar work load or power output or doing more exercise in a given time. Improvements in endurance may be due to several factors, including more availability of oxygen from the blood to the exercising muscles, greater use of aerobic processes (the most efficient energy sources), lower blood lactate levels, or greater anaerobic capacity. Adaptation to submaximum exercise is associated with a lower rate pressure product (systolic blood pressure multiplied by heart rate) for a standard exercise task. Changes in the skeletal muscles tend to improve accessibility to oxygen from the blood because of the higher myoglobin concentration, which enhances oxygen transport and the greater capillary density from which oxygen must be diffused. A greater concentration of oxidative enzymes allows muscles to obtain a larger share of their energy from aerobic rather than anaerobic sources. In so doing, the amount of high energy phosphates generated from each mole of substrate metabolized is much greater, resulting in increased efficiency of substrate use. Lactate accumulation is also decreased and the metabolic anaerobic threshold increased. Available muscle glycogen is a determinant of endurance time at higher submaximum work intensities. Since muscle glycogen is higher after training, the time

21 2306 Special Report Circulation Vol 82, No 6, December 1990 required to deplete it would be expected to increase, which has been shown to augment endurance.75 Key Point: Submaximum endurance is increased with training due to changes in the muscle cells, allowing more aerobic activity and providing more glycogen for anaerobic energy. Preventive value of exercise conditioning Habitual exercise eliminates one of the risk markers associated with a higher incidence of CAD. Other risk factors include age, gender, hypertension, hyperlipidemia, cigarette smoking, obesity, diabetes mellitus, and family history. The Centers for Disease Control have proclaimed that inactivity is a major risk factor with an overall weight for preventive value similar to cholesterol, cigarette smoking, and high blood pressure.76 Some of the preventive value of exercise is related to associated improvements in other risk factors, but exercise seems to exert an independent effect as well. Changes in risk factors that accompany exercise training include the following: * Decrease in blood pressure * Increase in high-density lipoprotein cholesterol level * Decrease in triglyceride level * Augmentation of weight reduction efforts * Psychological effects - Less depression - Reduced anxiety * Improved glucose tolerance Although no randomized, controlled studies have been performed, several prospective population studies have reported lower heart attack and death rates in active, apparently healthy populations compared with their sedentary counterparts. This association has been observed during leisure activity,77'78 total daily activity,79 and occupational activity.80 Some of this protection is no doubt due to modification of risk factors, but some is an independent effect of exercise. The mechanism of the independent effect is not known. Whatever the mechanism, the benefits of exercise outweigh the risks, even with vigorous exercise.81 Key Point: Sedentary lifestyle is a key independent risk factor for developing CAD. Exercise needed for an optimum effect Activity performed for training should be assessed in terms of intensity, frequency, duration, mode, and progression. The intensity of activity needed to improve physical conditioning probably varies among individuals and may be as little as 50% of Vo2 max for 20 minutes three times per week. An exercise intensity-duration relation is likely, so low-intensity exercise requires more time to increase functional capacity than higher intensity exercise. From a health and conditioning standpoint, the major advantage of moderate- and low-intensity exercise is less likelihood of complications, whereas vigorous exercise has the advantage of accomplishing the goal in less time. Total work performed is usually expressed as kilocalories. Experience with normal populations suggests that activity equal to or greater than 700 kilocalories per week is associated with higher maximum working capacities. Morbidity and mortality from heart attacks may also be related to amount of exercise. One group concluded that individuals whose activity score was 28 or less had a higher incidence of CAD (myocardial infarctions, angina pectoris, and sudden death) than those whose score was higher.79 In the study, activity score was determined by weighting activity by intensity and time so that 1 unit of score approximated 1 hour multiplied by 1 MET. Studies of college alumni whose jobs were sedentary concluded that mortality and morbidity were lowest in those whose activities required an average of 2,000 kilocalories per week or more.78 More recent studies have shown advantages of physical activities conducted at 35-40% of Vo2maxbut with greater frequency and duration.82 Table 10 lists energy requirements of various activities. Activities that are 60% of Vo2 max are generally categorized as moderate. Body weight must be used to calculate calories since METs are corrected for weight. The following conversion formula is used: Calories/min= (METs x 3.5 x kg weight)/200. A threshold of intensity is probably required to achieve benefit, although the exact value is not known and may vary from one person to another. Although a threshold cannot be defined from available information, much of the exercise described in published reports and associated with good health is moderate in intensity, such as walking. Thus, exercise likely need not be of high intensity to be beneficial, and total amount of activity is more important for health than higher intensities. Vigorous exercise such as jogging and running also seems beneficial. In one study,81 individuals who regularly performed vigorous exercise had an overall lessened likelihood of sudden death. More orthopedic injuries and higher dropout rates are associated with high-intensity exercise compared with low- to moderate-intensity programs. However, this does not mean that better guidelines could not reduce the risk of vigorous exercise further, providing an even greater overall benefit. Hence, these recommendations are directed toward minimizing risk and maximizing benefit. Occupational activity Early studies of longshoremen suggest that occupational activity can provide protection from CAD.80 Occupational activity was also considered a part of overall activity in another study.78 The level of physical effort required of longshoremen was great and is rarely duplicated in the United States today because of widely available mechanical devices. An operational definition of occupational activity is a job that requires lifting loads of 20 pounds or more at least once an hour throughout the day or constantly moving loads of any size from one place to another without mechanized transportation. In the longshoremen study, frequent walking or standing had no protective value, although other studies suggest that individuals who walk for long periods of time

22 TABLE 10. Estimated Energy Requirements of Selected Activities* Mild Baking Billiards Bookbinding Canoeing (leisurely) Conducting an orchestra Dancing, ballroom (slow) Golf (with cart) Horseback riding (walking) Playing a musical instrument: Accordion Cello Flute Horn Piano Trumpet Violin Woodwind Volleyball (noncompetitive) Walking (2 mph) Writing Moderate Calisthenics (no weights) Croquet Cycling (leisurely) Gardening (no lifting) Golf (without cart) Mowing lawn (power mower) Playing drums Sailing Swimming (slowly) Walking (3 mph) Walking (4 mph) Vigorous (METs) Badminton 5.5 Chopping wood 4.9 Climbing hills No load 6.9 With 5-kg load 7.4 Cycling (moderately) 5.7 Dancing Aerobic or ballet 6.0 Ballroom (fast) or square 5.5 Field hockey 7.7 Ice skating 5.5 Jogging (10-minute mile) 10.2 Karate or judo 6.5 Roller skating 6.5 Rope skipping 12.0 Skiing (water or downhill) 6.8 Squash 12.1 Surfing 6.0 Swimming (fast) 7.0 Tennis (doubles) 6.0 *These activities can often be done at variable intensities, assuming that the intensity is not excessive and that the courses are flat (no hills) unless so specified. Categories are based on experience of tolerance; if an activity is perceived to be more than indicated, it should be judged accordingly. MET, metabolic equivalent (3.5 ml * kg- minm' oxygen uptake). (such as postal employees) obtain protection. It is likely that unless individuals walk for 1 hour or more each day (low to moderate intensity), they should supplement that activity with leisure-time exercise. Exercise recommendations for men and women Gender is an important factor in formulating risk for CAD, and much additional research is needed Writing Group Exercise Standards 2307 to define the exercise needs of women. Women require approximately the same intensity, frequency, and duration of exercise as men.83 However, most studies of heart disease prevention reported to date have focused on men because of the higher incidence of CAD in men. Requirements and recommendations for prevention of heart disease in women may differ somewhat from those developed from data collected on men. However, women do develop CAD, and it is a major cause of mortality and morbidity. Until more research is complete, it seems prudent to recommend the same guidelines for exercise in men and women. Recommendations for maintenance of cardiovascular health Occupational activity. Unless an individual's occupation meets minimum required exercise of sustained moderate or heavy intensity, a leisure-time exercise program should be followed. Occupational activity is defined as adequate if it requires continual climbing of stairs or inclines, lifting loads of 20 pounds or more each hour, or carrying loads of any size continuously throughout the day. Very few jobs require such energy expenditure now because of automation and the use of mechanized lift devices. Leisure-time activity. Leisure-time activity for minimum conditioning and health benefits should consume a minimum of 700 calories per week on 3 or more nonconsecutive days (the amount associated with improved conditioning). Individuals should be encouraged to engage in activities requiring up to 2,000 calories per week for maximum health benefits. Walking 20 miles each week is one way to accomplish this goal. Key Point: Regular physical activity is important for health maintenance. Walking appears to be as beneficial as more vigorous activities. Some benefit is apparently derived from as little as 20 minutes of low-intensity exercise performed three times per week. However, incremental benefits appear to accrue from up to 2,000 calories per week (20 miles of walking or jogging). There is no evidence of a health benefit at more than 2,000 calories per week. Occupational activity provides adequate health benefits only when a job requires sustained activities. Regular physical activity is recommended for both men and women. Exercise training techniques Activities that cause the greatest increase in V02 max have certain characteristics that, when present, are said to qualify the exercise as endurance or cardiovascular. These characteristics include dynamic exercise, alternately contracting and relaxing the muscles (as opposed to isometric or static exercise), and large muscle group activities such as walking or running. Exercise must be performed at least three times per week for a minimum of minutes per session, at a minimum intensity of 50-60% Vo2 ma, In addition to walking and running, other examples of endurance or cardiovascular activities are swimming, cycling, and cross-country skiing.

23 2308 Special Report Circulation Vol 82, No 6, December 1990 Exercising at a low intensity for 5-10 minutes before and after the training session is a routine recommendation. Such activities help stretch tissues after inactivity and prepare muscles for the activity session. The cool-down period also prevents hypotension, which may occur with sudden cessation of exercise.84 Properly selected calisthenics and resistance exercises are helpful for promoting muscle strength and flexibility, which are important components of physical conditioning. These activities may include stretching and weight training exercises. Flexibility and strength exercises have less value for increasing Vo2 mthan activities that are usually recommended for cardiovascular endurance, but other benefits justify their performance. When guidelines are properly followed, there is no evidence that such exercises are hazardous in apparently healthy individuals. Flexibility and strength activities should be carefully selected. All exercises should be initiated at low intensities and increased with adaptation. A usual starting guideline is to use weights that are 40-50% of the maximum that can be lifted for one full exercise sequence. These are repeated 8-10 times and increased by 5% as adaptation occurs. Exercise should strengthen the major muscle groups of the legs, trunk, and arms. Dynamic exercise using good posture and breathing technique should be emphasized. Slow movements taken through a full range of motion using moderately heavy weights are recommended. Professional advice should be sought if heavier weights are used. Key Point: Physical activity should consist of cardiovascular exercise preceded by a warm-up period and followed by a cool-down period. Calisthenics are useful for promoting strength and flexibility but probably do not contribute to cardiovascular health. Medical clearance for physical activity in apparently healthy populations Medical history. Of particular interest are items in the history that indicate unsupervised exercise may be hazardous, including CAD, significant valvular heart disease, cardiomyopathy, congenital heart disease, and orthopedic problems. If any of these heart conditions are present, the individual should follow the guidelines for individuals with heart disease in the next section. Persons taking cardiovascular medications should also follow the guidelines found in the next section. Obesity tends to increase the risk of orthopedic injury; thus, lower intensity exercise in such persons is preferred. Symptoms. Symptoms suggesting cardiovascular or pulmonary disease should be evaluated to exclude the presence of such disease. They include chest discomfort, shortness of breath (after climbing one flight of stairs or less), and leg discomfort consistent with claudication. Physical examination. Hypertension requires assessment and management. Murmurs suggesting significant valvular heart disease or other signs of cardiac disease (congestive heart failure, ischemia, etc.) should be regarded as indicating the presence of cardiovascular disease until proven otherwise. Detection of occult disease. One of the most difficult tasks a physician may undertake is detection of occult disease. It is well known that individuals can have significant CAD in the complete absence of symptoms or signs, the presence of a normal ECG, and a normal exercise test. However, the exercise test is the best method for detecting occult CAD. Medical clearance strata 1. A recent medical history and physical examination should be done. a. If history or physical finding indicates significant cardiovascular disease, the person should be treated as noted in the section "Exercise Training of Individuals With Cardiovascular Disease." Examples of cardiovascular disease include previous myocardial infarction, CABS, angina pectoris, valvular heart disease (except most cases of mitral valve prolapse), and cardiomyopathy. b. If the individual knows of no cardiovascular disease but has symptoms or signs that suggest the presence of significant disease or major coronary risk factors, an exercise test is needed to exclude the presence of a high-risk condition. If an exercise test cannot be performed, activity should be limited as outlined in the next section. Examples include intracardia lesions of uncertain severity (septal defects, va ve abnormalities), symptoms suggesting angina, and certain murmurs. 2. The individual's age should be considered. a. If the individual is less than 40 years old, no further workup is needed and the individual can be cleared for any activity if no. 1 above is normal. b. If the individual is 40 years of age or older: 1) An exercise test should be recommended if vigorous exercise is planned. If the test is normal, no further restrictions are needed. If the test is abnormal, the individual should be treated as if he or she has heart disease. 2) If the individual chooses not to undergo an exercise test, he or she should follow the activity guidelines outlined in the next section. Key Point: The medical clearance stratification enables physicians to classify individuals by activity and to give advice and options for physical activity programs. If the medical clearance strata outlined above is followed, all patients may be placed in one of the categories below. Activity classification. After the medical clearance stratification is complete, patients can be classified by risk, based on their characteristics. The following classifications are recommended. Class A: Apparently healthy. There is no evidence of increased risk for exercise. Includes 1) individuals under age 40 who have no symptoms of or known presence of heart disease or major risk markers and 2) individuals of any age without known heart disease or major risk markers and who have a normal exercise test.

24 Activity guidelines: No restrictions other than basic guidelines ECG and blood pressure monitoring: Not required Supervision required: None Class B: Presence of known, stable cardiovascular disease with low risk for vigorous exercise but slightly greater than for apparently healthy individuals. Moderate activity is not believed to be associated with increased risk in this group. Includes individuals with 1) CAD (including myocardial infarction, CABS, PTCA, angina pectoris, abnormal exercise test, and abnormal coronary angiograms) whose condition is stable and who have the clinical characteristics outlined below; 2) valvular heart disease; 3) congenital heart disease; 4) cardiomyopathy; and 5) exercise test abnormalities that do not meet the criteria outlined in C and D below. Clinical characteristics: 1) NYHA class 1 or 2; 2) exercise capacity over 6 METs; 3) no evidence of heart failure; 4) free of ischemia or angina at rest or on the exercise test at or below 6 METs; 5) appropriate rise in systolic blood pressure during exercise; 6) no sequential premature ventricular contractions; and 7) ability to satisfactorily self-monitor intensity of activity. Activity guidelines: Activity should be individualized with exercise prescription by qualified personnel or restricted to walking. ECG and blood pressure monitoring: Only during prescription procedures. Supervision required: Medical supervision during prescription sessions and nonmedical supervision for other exercise sessions if the individual understands how to monitor his or her activity. Class C: Presence of known, stable cardiovascular disease with low risk for vigorous exercise but unable to self-regulate activity or to understand recommended activity levels. Includes same individuals outlined above in class B. Clinical characteristics: Same as class B, except unable to self-regulate activity. Activity guidelines: Activity should be individualized with exercise prescription by qualified personnel and supervised by nonmedical personnel trained in basic CPR or with electronic monitoring at home. ECG and blood pressure monitoring: Only during prescribed procedures. Supervision required: Medical supervision during prescribed sessions and nonmedical supervision during other exercise sessions to help individual regulate activity. Class D: Those at moderate to high risk for cardiac complications during exercise. Includes individuals with 1) CAD with clinical characteristics outlined below; 2) cardiomyopathy; 3) Writing Group Exercise Standards 2309 valvular heart disease; 4) exercise test abnormalities not directly related to ischemia; 5) previous episode of ventricular fibrillation or cardiac arrest that did not occur in the presence of an acute ischemic event or cardiac procedure; 6) patients with complex ventricular arrhythmias that are uncontrolled at mild to moderate work intensities with medication; 7) individuals with three-vessel disease or left main disease; and 8) individuals with low ejection fractions (less than 30%). Clinical characteristics: 1) Two or more myocardial infarctions; 2) NYHA class 3 or greater; 3) exercise capacity less than 6 METs, ischemic horizontal or downsloping ST depression of 4.0 mm or more, or angina during exercise; 5) fall in systolic blood pressure with exercise; 6) a medical problem that the physician believes may be life-threatening; 7) previous episode of primary cardiac arrest; and 8) ventricular tachycardia at a work load of less than 6 METs. Activity guidelines: Activity should be individualized with exercise prescription by qualified personnel. ECG and blood pressure monitoring: Continuous during rehabilitation sessions until safety is established, usually in 6-12 sessions or more. Supervision: Medical supervision during all rehabilitation sessions until safety is established. Class E: Unstable disease with activity restriction. Includes individuals with 1) unstable ischemia; 2) heart failure that is not compensated; 3) uncontrolled arrhythmias; 4) severe and symptomatic aortic stenosis; and 5) other conditions that could be aggravated by exercise. Activity guidelines: No activity is recommended for conditioning purposes. Attention should be directed to treating the patient and restoring him or her to class D or higher. Daily activities must be prescribed based on individual assessment by the patient's personal physician. The above classifications are presented as a means of beginning exercise with the lowest possible risk. As the individual gains experience, the decision may be made to place the patient in another category. In most cases, as safety of exercise and improvement in working capacity are demonstrated, graduation to classes nearer A and B is appropriate. Key Point: An activity classification is offered to help the physician decide on activity guidelines, monitoring, and supervision required for various conditions. Exercise prescription Exercise for individuals with cardiovascular disease should be prescribed as outlined in the section "Exercise Training of Individuals With Cardiovascular Disease." Guidelines for physical activity for apparently healthy individuals are recommended below. A useful approach to activity prescription is to identify the desirable rating of perceived exertion and ask individuals to adhere to that intensity. A

25 2310 Special Report Circulation Vol 82, No 6, December 1990 suggested rating of perceived exertion for most healthy individuals is 3 to 5 (moderate to heavy) on a Borg scale of 1 to 10, an approach that is both effective and acceptable.85 See Table 6 for more details on rating of perceived exertion. In addition, the individual should carefully follow the instructions he or she is given. Guidelines for Cardiovascular Exercise 1. Exercise only when feeling well. Wait until symptoms and signs of a cold or the flu (including fever) have been absent 2 days or more before resuming activity. 2. Do not exercise vigorously soon after eating. Wait at least 2 hours. Eating increases the blood flow requirements of the intestinal tract. During vigorous exercise, the muscles' demands for blood may exceed the ability of the circulation to supply both the bowel and the muscles, depriving organs of blood, resulting in cramps, nausea, or faintness. 3. Adjust exercise to the weather. Exercise should be adjusted to environmental conditions. Special precautions are necessary when exercising in hot weather, and signs of overheating may not be recognized. It is difficult to define when it is too hot to exercise since air temperature is greatly influenced by humidity and air movement (wind), which are not easy to measure. The following guidelines are recommended for a noncompetitive workout: If air temperature is over 700 F, slow the pace, be alert for signs of heat injury, and drink adequate fluids to maintain hydration. A good rule to follow is to exercise at the usual workout pace (rating of perceived exertion 3 to 5), which will be a slower pace or lower work intensity. Adaptation to moderate levels of heat is gradual, requiring days. Accommodation to extreme heat never occurs. Signs of heat injury may be varied at the onset; hence, any symptom should be regarded as evidence of heat overload. The following indications of heat stress are particularly likely to occur: headache, dizziness, faintness, nausea, coolness, cramps, and palpitations. If any of these indications are present, stop exercising immediately and go to a cool environment. If the air temperature is over 800 F, exercise in the early morning or late afternoon in shaded areas to avoid the heat. Air-conditioned shopping malls are popular. Exercise is better tolerated if humidity is low and there is a breeze. Exercise in the heat causes excessive fluid loss, so adequate fluid intake is important before, during, and after each session. 4. Slow down for hills. Watch for hills. When ascending hills in the exercise course, decrease speed to avoid overexertion. Again, a useful guide is to maintain the same rating of perceived exertion as in a usual workout. 5. Wear proper clothing and shoes. Dress in loose-fitting, comfortable clothes made of porous material appropriate for the weather. Use sweat suits only for warmth. Never use exercise clothing made of rubberized, nonporous material. In direct sunlight, wear light-colored clothing and a cap. Wear shoes designed for exercise (walking, jogging, etc.). 6. Understand personal limitations. Everyone should undergo periodic medical examinations. When under a physician's care, ask if there are limitations that might interfere with the program. 7. Select appropriate exercises. Cardiovascular (aerobic) exercises should be a major component of activities. However, flexibility and strengthening exercises should also be considered for a well-rounded program. 8. Be alert for symptoms. If the following symptoms occur, contact a physician before continuing exercise. Although any symptom should be clarified, these are particularly important: a. Discomfort in the upper body, including the chest, arm, neck, or jaw, during exercise. The discomfort may be of any intensity and may be present as an aching, burning, tightness, or sensation of fullness. b. Faintness accompanying the exercise. Sometimes brief light-headedness may follow unusually vigorous exercise or too short a cool-down period. This condition does not usually indicate heart disease and may be managed by exercising at a lower intensity with a gradual cool-down at the end of the session. If a "fainting spell" or feeling of faintness occurs during exercise, discontinue the activity until after a checkup by a physician. c. Shortness of breath during exercise. During exercise, rate and depth of breathing should increase but should not be uncomfortable. A useful rule is that breathing should not be so difficult that talking is an effort, wheezing develops, or more than 5 minutes are required for recovery. d. Discomfort in bones and joints either during or after exercise. There may be slight muscle soreness when beginning exercise, but if back or joint pain develops, discontinue exercise until after a checkup by a physician. 9. Watch for the following signs of overexercising: a. Inability to finish. Training sessions should be completed with reserve. b. Inability to converse during the activity. Breathing normally increases during exercise but should not be uncomfortable. When a conversation cannot be conducted during exercise because of trouble breathing, the conditioning activity may be too intense. c. Faintness or nausea after exercise. A feeling of faintness after exercise may occur if the activity is too intense or has been stopped too abruptly. In any event, decrease the intensity of the workout and prolong the cool-down period. d. Chronic fatigue. During the remainder of the day or evening after exercise, an individual should feel stimulated, not tired. If too fatigued during the day, intensity and/or duration of the workout should be decreased.

26 TABLE 11. Injuries by Age and Activity n Age Activity Injuries (%) Walking/jogging Walking/jogging Walking/jogging Walking/jogging Walking 12 From Pollock and Wilmore.85(p392) Reproduced with permission. e. Sleeplessness. If unable to sleep well despite feelings of fatigue, the amount of activity should be decreased until symptoms subside. Insomnia is particularly likely during distance training. A proper training program should make it easier, not more difficult, to have a good night's rest. f. Aches and pains in the joints. Although there may be some muscle discomfort, joints should not hurt or feel stiff. Check exercise procedures, particularly stretching and warm-up exercises, to ensure that you are using the correct technique. Muscle cramping and back discomfort may also indicate poor technique. If symptoms persist, check with a physician before continuing. 10. Start slowly and progress gradually. Allow time to adapt. Key Point: General guidelines can provide an activity prescription for apparently well individuals. The benefits of exercise outweigh the risks when such an approach is used. Noncardiovascular injuries Musculoskeletal injuries are most common and include direct injuries such as bruises, sprains, and strains, and indirect problems such as arthritis and back pain. The traumatic impact of exercise is usually classified as low and high impact. Low-impact exercises (walking, cycling, and swimming) cause little stress on bones and joints, whereas high-impact exercises (running and aerobic dancing) cause repeated impact on the knees, ankles, and feet. Studies of injuries during exercise show that two important factors in determining the frequency of injuries during exercise are age and the high impact nature of exercise. (See Table 11.) Therefore, it is recommended that any individual over age 40 should take special care to avoid highimpact activities.86 If such activities are chosen, they should be initiated at low levels and progressed slowly. A day of rest between exercise periods permits the body to gradually adapt to stresses and strains. More attention should also be given to warm-up and cool-down periods with stretching, lowlevel calisthenics, and low-level aerobic exercises. In general, fast walking is a well-tolerated, low-impact exercise that provides excellent results. Swimming and stationary cycling may also be appropriate. Several popular forms of exercise are classified by musculoskeletal impact in Table 12. TABLE 12. High impact Jogging/running Basketball Volleyball Hopping/jumping Rope skipping Aerobic dancing Downhill skiing Writing Group Exercise Standards 2311 Categories of Activity by Musculoskeletal Impact Low impact Walking/hiking Cycling Stationary cycling Swimming Rowing Cross-country skiing From Pollock and Wilmore.85(p393) Reproduced with permission. Exercise Training of Individuals With Cardiovascular Disease Types of cardiovascular disease Exercise training is obviously useful in treatment of CAD patients because the physiological changes that take place lessen ischemia at rest and during submaximum exercise. Physical activity is also associated with protection from development or progression87 of CAD. Certain precautions are necessary to avoid injury. In this section, the principles of surveillance for safety and expectations for improvement are largely directed to CAD but may also apply to many noncoronary cardiac, vascular, and pulmonary diseases. Safety is the major reason for establishing special guidelines for patients with cardiovascular disease. Recommendations should be considered appropriate for any condition associated with a higher than normal risk for sudden cardiac arrest or myocardial infarction during exercise, but if carefully followed, could benefit the individual by an increase in physical working capacity. The following list includes conditions in which physical working capacity increases with regular exercise conditioning and for which surveillance is recommended: * Abnormal exercise test indicating ischemia * Angina pectoris * Myocardial infarction * CABS * PTCA * Heart transplant * Cardiomyopathies * Valvular heart disease * Hypertension * Pacemakers Key Point: Regular physical activity is beneficial in the presence of cardiovascular disease if prudent guidelines are followed. Risk of sudden death Cardiac disease seems to impart higher risks for sudden cardiac arrest during vigorous exercise (such as jogging) than in normal individuals. However, with judicious programs, activity is clearly beneficial. The most compelling argument for exercise training in cardiac patients is that randomized controlled trials show a lower death rate in exercising groups compared with sedentary groups,87 indicating that exercise is safe and beneficial. However, those studies were performed under strictly controlled conditions

27 2312 Special Report Circulation Vol 82, No 6, December 1990 and similar results can be expected only if careful guidelines are followed. The random incidence of sudden cardiac arrest in populations with CAD has been estimated to be 1 in 80,000 to 160,000 manhours.88 Type and intensity of activity and use of monitoring seem to have a special impact on incidence of sudden cardiac arrest as seen in Table 9, which shows that in cardiac patients, incidence is lowest during activities that are largely controlled, such as walking, cycling, or treadmill walking. Table 9 also suggests that continuously monitored activities have the lowest rates of sudden cardiac arrest compared with those that are only intermittently monitored or unmonitored. Obviously, these studies cannot answer the question about the relative contributions of each of the potential variables to sudden cardiac arrest. However, they strongly suggest that incidence of sudden cardiac arrest is similar in all mixed activities to that expected by chance alone. This, in turn, suggests that jogging has a higher than expected incidence of sudden cardiac arrest. The higher incidence of sudden cardiac arrest during jogging in patients with heart disease is probably related to intensity. Jogging at even the slowest pace generates a Vo2 that is from 80% to 100% of maximum for most untrained individuals. If individuals with cardiac disease jog, they should do so under medical supervision. Monitoring is important because it helps the individual establish an appropriate exercise pace, which is about 60-70% of VO2ma This pace can best be learned during monitored sessions. Key Point: The risks of exercise for sudden cardiac arrest and myocardial infarction are higher in individuals with known heart disease who engage in vigorous physical activity such as jogging. Hence, individuals with heart disease should either exercise under medical supervision or restrict their activity to a moderate-intensity activity such as walking. Monitoring during exercise is recommended for all individuals with heart disease until tolerance of the activity has been demonstrated. Physiological changes Although physical working capacity increases with training when heart disease is present, reported physiological changes have differed somewhat from those reported in apparently healthy individuals and are outlined below. Maximum oxygen uptake. Patients with CAD have an increase in VO2ma with training. The magnitude of the change is less in patients with heart disease than observed in apparently healthy individuals, but the increase is noteworthy and the maximum heart rate may be the same or slightly greater after training in those with heart disease.64 The least increments are seen in individuals with heart failure, but even in these patients, the improvement is of great rehabilitative value for restoring ability to perform daily activities. Cardiac output. The increase in maximum cardiac output is due to an increase in both stroke volume Heart rate (bpm) x Systolic pressure (mm Hg) A A 25,000 0X 20,000 x /,/ / 0 15,000 X/ X, before conditioning / C), 0 after conditioning // 10,000 X 0 Rest Work intensity in watts FIGURE 6. Change in double product before and after exercise rehabilitation. Double product (heart rate times systolic pressure) is shown at rest, during exercise, and during angina (A). After conditioning, more work can be tolerated because double product (and hence myocardial oxygen uptake) is lower. From Redwood et al.90 Reproduced with pernission. and maximum heart rate, which differs from normal subjects, whose maximum heart rate usually does not change. In patients with cardiac disease, the submaximum cardiac output may be lower with maintenance of Vo2 by widening the avo2 difference after training.89 Such a result suggests improved overall efficiency for delivery of oxygen to the tissues. Decreased myocardial oxygen uptake. Exercise training has special significance in individuals with CAD because the direction of changes promotes lower Mo2. Changes associated with lower Mo2 are lower heart rate, lower circulating catecholamines, and lower systolic blood pressure. The benefits of these adjustments can be demonstrated by the greater amount of work that can be done before angina or ECG-determined ST depression occurs.90 Figure 6 reflects the positive effects of conditioning exercise on angina. Collateral fornation. Present knowledge does not support the concept that collateral circulation is likely to develop in the coronary arterial tree as a result of exercise conditioning. Improvement of ischemia is believed most likely to occur by reducing Mo2 rather than increasing supply. Improved myocardial function. Animal studies have shown increased contractility and resistance to hypoxia with exercise training. Human data have not consistently shown improved myocardial performance.91 Thallium-201 perfusion. Studies do not show improvement in thallium-201 scans after training in patients with CAD. Key Point: Individuals with heart disease increase their working capacities in much the same way as

28 normal subjects. A major adjustment that is beneficial in patients with CAD is the lowering of myocardial oxygen demand, which in turn lessens ischemia. Collateral formation in the coronary arterial tree and improved myocardial performance may occur with exercise in some cases but not with regularity. Secondary prevention Coronary risk profile. Exercise training induces improvement in the coronary risk profile. Reductions in blood pressure, triglycerides, and body fat, improved glucose tolerance, and increase in high-density lipoprotein cholesterol are examples that seem to occur in individuals with CAD, although they usually are most marked in individuals who can perform large amounts of exercise. Exercise is also associated with an improved mental outlook. Specifically, standard psychological tests have documented less depression and anxiety.92 Lessening of depression is particularly important in postmyocardial infarction patients, who tend to have clinical depression. Although postinfarction depression is self-limited, regular exercise probably hastens improvement. Morbidity and mortality. The large number of subjects required and the need for careful follow-up of those subjects for long periods of time have precluded a definitive, randomized, controlled trial of cardiac rehabilitation. Several smaller studies have been conducted, and although most show a beneficial trend, none are large enough to draw definitive conclusions. A meta-analysis of the randomized, controlled trials that examined the influence of cardiac rehabilitation on outcome has shown a distinct benefit that seems largely the result of exercise.87 The significant benefit is reduction of sudden cardiac death; no significant reduction in reinfarction could be demonstrated. Although exercise was an integral part of the programs of all these studies, they were multifactorial in nature. In addition, all exercise was moderate in intensity and supervised. Return to work. The use of exercise early after infarction has also been evaluated and compared with bed rest. In many studies, physical activity soon after myocardial infarction promotes earlier discharge from the hospital and greater likelihood of returning to usual activities.93 Key Point: Although no reduction in frequency of myocardial infarction has been shown, regular physical activity is associated with improved survival when combined with other interventions such as diet. Other benefits include earlier discharge from the hospital and greater likelihood of returning to work after myocardial infarction. Procedures and techniques for exercise in cardiac rehabilitation Precautions. All individuals must be carefully screened for medical status before beginning an exercise program. They must also have adequate instruction and follow-up to prevent the development of a condition that would make exercise hazardous. Writing Group Exercise Standards 2313 Any cardiac condition that exercise might aggravate should be avoided. Systemic infections. Acute systemic infections can be adversely affected by activity. Even individuals with chronic infections may benefit more from rest than exercise. However, as the infection responds to treatment, exercise can begin. For example, in the treatment of bronchitis, moderate exercise can begin when the individual has normal temperature, white blood cell count, and cultures. Local infections are probably not affected by exercise as long as the activity does not irritate the lesion. Thromboembolic disease. Thrombophlebitis, arterial embolism, or pulmonary embolus should be treated with rest, even though factors that cause clot dislodgment are not clearly defined. Low-level walking or range-of-motion exercise is probably safe as soon as the individual is in a stable treatment program and has had no recurrence of symptoms. The individual can begin a moderate exercise program when anticoagulants have been discontinued or 6 weeks of anticoagulant therapy have passed since the last symptoms or signs of thromboembolism. Endocarditis. It is prudent for individuals with vegetative endocarditis to avoid exercise until the disease is stable. The contribution of physical activity to emboli is not known for certain, but low-tomoderate activity levels seem prudent until the course of antibiotics is completed. Neuromuscular diseases. Neuromuscular inflammation and injuries should be evaluated by a qualified rheumatologist, orthopedist, or physiatrist to assess the desirability of physical activity and to determine the types of activities that are suitable. Cardiovascular disease complications. HEART FAILURE. Stable cardiovascular disease does not seem to be worsened by low-to-moderate physical activity. On the contrary, individuals with uncompensated heart failure have developed fulminant pulmonary edema with exercise. Therefore, exercise is not recommended if the patient's condition is unstable. MYOCARDITIS. As with any infection, activity should be maintained at low levels until the individual has no signs of active infection. When the infection has subsided, there is no evidence of harm if exercise is prescribed prudently. AcuTE ISCHEMIA. Individuals with unstable ischemic heart disease as judged by anginal symptoms or a changing pattern in the ECG should not exercise. Such individuals may develop "global" ischemia and shock. ARRHYTHMIAS. Although there is some evidence that regular physical activity may be helpful for patients with arrhythmias, most studies have focused on benign arrhythmias. The occurrence of exercise-induced high-grade ventricular ectopy (three or more sequential ventricular premature beats) may be hazardous, and vigorous exercise should be avoided. The usual strategy is to prescribe activity that generates a lower heart rate than that associated with abnormalities. In general, individuals with arrhythmias other

29 2314 Special Report Circulation Vol 82, No 6, December 1990 than high-grade ventricular ectopy may exercise if they are asymptomatic and remain hemodynamically stable. Monitoring during rehabilitative sessions may be helpful for adjusting drug treatment for arrhythmias. ELECTRONIC PACEMAKERS. If performance in an exercise test is satisfactory, individuals with pacemakers are no more prone to problems than other cardiac patients. Although the paced rate of some pacemakers can be accelerated during exercise, many cannot. Physical activity intensities in fixed-rate pacemakers must be gauged by a method other than pulse counting, such as defining specific work loads that are about 60-70% of peak working capacity on the exercise test. This can be ascertained by using the rating of perceived exertion. SURGICAL INCISION AFTER CORONARY ARTERY BY- PASS SURGERY. The extent of healing of surgical incisions from CABS is the most limiting factor. Hence, the decision to start activity is often surgical. Low-level activities are usually acceptable hours after surgery. The same precautions should be exerted for CABS patients as for postmyocardial infarction patients. Prescribed physical activity. Prescribed physical activity is beneficial and safe because it helps patients restrict intensities to low-risk levels. Moderate activity actually means exercise that is less than or equal to 75% of Vo2.aX This intensity is effective for increasing Vo2max if performed on a regular basis and at an intensity associated with a low incidence of sudden cardiac arrest. Exercise tests. Exercise tests are an important part of the rehabilitative process. They provide initial levels of working capacity, specific precautions, and heart rates used to prescribe activity. Tests are useful for assigning risk stratification. Exercise tests should be repeated at least yearly and perhaps 4-6 weeks after program entry to rewrite the exercise prescription for postmyocardial infarction patients or patients with chronic CAD who enter cardiac rehabilitation programs. Rehabilitation sessions. Rehabilitation sessions are follow-up sessions in which the patient is taught good health behaviors, including proper diet and lifestyle modifications such as smoking cessation and exercise. Rehabilitation sessions are conducted to teach exercise techniques of intensity, duration, frequency, mode, and progression. Activity is monitored during these sessions to ensure safety. The number of monitored sessions needed depends on the clinical circumstances. In some cases, only one or two sessions may be needed, but in others, three or four sessions per week over several months are necessary. Monitoring of activity. Symptoms. CHEST DISCOM- FORT suggesting ischemia, which may appear as chest tightness, fullness, pressure, or dull pain in the anterior precordium and may radiate to the neck or arm. SHORTNESS OF BREATH may suggest pulmonary congestion, and appropriate assessment for pulmonary edema is needed. Some shortness of breath and fatigue will occur because of the deconditioning effect of bed rest after a cardiovascular event or surgery, but the difference is usually obvious. Edema on the chest x-ray film, rales, or a ventricular third heart sound on examination will clarify the presence of significant pulmonary edema. FAINTNESS (or light-headedness) is common after a period of inactivity. This symptom does not necessarily have cardiac implications since it is often due to a contracted blood volume or loss of postural reflexes caused by inactivity or surgery. Even so, individuals who become faint usually have a fall in blood pressure that could be hazardous if unattended. Having the individual sit up will usually allow restitution of plasma volume or reflexes or both in a few hours. If the change in posture does not resolve orthostasis, fluids may be needed. WEAKNESS is a common symptom after a confining illness and need not be of concern. The sensation of fatigue will usually improve with time and conditioning. Weakness after open-heart surgery is particularly likely to occur because of low hemoglobin and may persist, interfering with the early phases of cardiac rehabilitation. Restitution of hemoglobin to normal requires several weeks without transfusion. Heart rate. A target heart rate should be considered when exercise is prescribed. The target heart rate is usually determined from the exercise test, but if an exercise test has not been done for predischarge activity progression, a useful goal is to avoid increases of more than 20 beats/min over resting. Blood pressure. Blood pressure should be under control at the start of an exercise program. Specific guidelines for resting levels are difficult to set, but in general, activity should be restrained until the clinician is satisfied with resting levels. A slight increase in systolic pressure may precede exercise training sessions due to anticipation and is not a cause for concern. Increments in systolic blood pressure during exercise are normal. However, if systolic blood pressure falls, the reason must be determined and therapy initiated before proceeding. Physical activity after myocardial infarction, coronary artery bypass surgery, or percutaneous transluminal coronaty angioplasty. Early exercise. Walking is recommended as the major mode of exercise for postinfarction patients unless the individual can attend classes where other monitored activities can be provided. Walking near the bedside and to the bathroom are permitted initially. If the individual becomes symptomatic, he or she can quickly return to bed. Encouraging the individual to sit up is an important part of this phase. Walking should start slowly and gradually increase as tolerated until 5-10 minutes of continuous movement is achieved. Active but nonresistive range of motion of upper extremities is also well tolerated early after myocardial infarction or CABS, as long as the activities do not stress the sternal incision. Initial activities should be monitored by a professional, and symptoms, rating of perceived exertion,

30 TABLE 13. Guidelines for Helping Patients Resume Walking Soon After Myocardial Infarction Before exercise Ask about chest discomfort, dyspnea, and faintness (if present, check with physician before proceeding). Measure blood pressure and heart rate (if more than 160/100 or less than 90/60 mm Hg or if heart rate is over 110 or under 60 beats/min, check with physician before starting). Check orthostatic blood pressure before beginning standing range-of-motion exercise or walking. If blood pressure falls more than 20 mm Hg or if fall is associated with symptoms of faintness, have patient lie down and notify physician. During exercise Ask patient to report symptoms, particularly chest discomfort, dyspnea, or faintness. If symptoms occur, discontinue exercise until checking with physician. Ask for rating of perceived exertion. Immediately after exercise Ask patient about symptoms. Measure heart rate, blood pressure, and rating of perceived exertion. If symptoms occur, blood pressure falls more than 20 mm Hg, or heart rate rises more than 20 beats/min over resting rate, check with physician before continuing. heart rate, and blood pressure measured and noted in the patient's records. When tolerance is documented, the individual can then perform that activity without supervision. Exercise within the first 2 weeks after myocardial infarction should focus on avoiding or offsetting the effects of bed rest. When the individual is stable as measured by ECG, vital signs, and symptomatic standards, he or she can begin walking. Although this activity is well tolerated and safe, certain precautions are recommended as outlined in Table 13. Late exercise. A symptom-limited exercise test is performed after the individual is stable and is walking without difficulty (as early as 2-6 weeks after hospital discharge). If more studies such as angiography are not indicated, a regular conditioning program can be initiated. Careful activity prescription is recommended. General principles of conditioning activity. For conditioning purposes, large-muscle group activities should be performed for at least 20 minutes, preceded by warm-up and followed by cool-down, at least three times per week. The intensity of exercise should be gauged by exercise prescription. Follow-up supervised group sessions are recommended to enhance the educational process, to ensure that the participant is tolerating the program, to confirm that progress is occurring, and to provide medical supervision in high-risk situations. A long-term follow-up should be encouraged at infrequent intervals (every 1-3 months) to encourage long-term compliance and to ensure that the program is being followed properly. General principles of exercise prescription Prescription in absence of ischemia or arrhythmias. Exercise intensity should approximate 50-85% of Vo2 nm, which can be ascertained by an exercise test. Writing Group Exercise Standards 2315 TABLE 14. Classification of Intensity of Exercise Based on Minutes of Endurance Training Relative intensity (No) RPE Intensity HRmax VO2 max (%) or HRma. reserve (%) <35 <30 <10 Very light Light Moderate Heavy >90 >85 >16 Very heavy HRmax, maximum heart rate (beats/min); Vo2 max, maximum oxygen uptake; RPE, rate of perceived exertion. From Pollock and Wilmore.85(p105) Reproduced with permission. (If a test is not done initially, the measurement of 20 beats/min above resting heart rate is adequate until testing is performed.) The steps in this process are as follows: 1. Prescription from the exercise test can be determined by finding the highest work load achieved on the exercise test and considering the training heart rate as that which occurred at the work load which was 60-90% of maximum heart rate or 50-85% of heart rate reserve ([maximum heart rateresting heart rate] x50-85%)+resting heart rate. That heart rate can be used for the prescription of many types of dynamic leg exercise. 2. Activities can be prescribed as the work intensity that achieves the training heart rate after 5-10 minutes at that work load (steady state). It may be expressed as watts on an ergometer, speed on a treadmill, or in METs. 3. If an individual wants to exercise but cannot assess intensity, then heart rate counting (manually or with a cardiotachometer) is useful. Heart rate counters are widely available and are generally fairly accurate for low to moderate intensity exercise. 4. If an individual intends to walk on a level surface, activity can be prescribed as the step rate found on a treadmill to generate the desirable heart rate.94 The usual procedure is to determine the step rate on a treadmill and prescribe it. Step rate can be easily measured as it requires less skill than counting heart rate. If this approach is used, individuals should be cautioned about avoiding hills. Walking in shopping malls or gyms can circumvent both hills and inclement weather. Exercise should be monitored for the first few sessions while the individual starts his or her activity. Monitoring assures that he or she understands the instructions and that the activity is well tolerated. 5. Individuals can also judge the intensity of exercise as the rating of perceived exertion, which can be equated to desirable heart rate during laboratory exercise and to their activities. The original scale is a 15-grade category scale ranging from 6 to 20, with a verbal description at every odd number. (See Tables 6 and 14.)

31 2316 Special Report Circulation Vol 82 No 6, December 1990 TABLE 15. Guidelines Exercise Training for Electrocardiographic Monitoring in Activity classification Monitoring A Apparently healthy Not required B Known stable CAD, low risk for vigorous exercise Monitored and supervised (usually 6-12 sessions) C Known stable CAD, low risk for Monitored and supervised vigorous exercise but unable to (usually 6-12 sessions or self-regulate or to understand more) recommended activity levels D Moderate to high risk for Monitored and supervised cardiac complications during (usually 6-12 sessions or exercise more) CAD, coronary artery disease. The following rating of perceived exertion values should be kept in mind: <12 light, 40-50% of maximum somewhat hard, 60-70% of maximum hard, 75-95% of maximum 6. Activities can progress as tolerance is demonstrated. The appropriate initial intensity of training is 50-60% of VO2max or a rating of perceived exertion of 12 to 13 on a scale of 6 to 20. After safe activity levels have been established, duration is increased in 5-minute increments per week. Later, intensities can be increased as heart rate response to exercise decreases with conditioning. Prescription in the presence of ischemia or arrhythmias. An exercise test is essential for this type of prescription. The manifestations of arrhythmias or ischemia that require such precautions can vary but usually include ventricular premature beats in sequence, an arrhythmia that is symptomatic or hemodynamically unstable, chest discomfort believed to be angina, ST depression of 2 mm or more, or fall in systolic blood pressure of 20 mm Hg or more. The exercise test is performed in the usual fashion, but the conditioning work intensity is derived from the heart rate associated with the abnormality. If the exercise test continues to a high level of effort, the heart rate at 50-60% of heart rate maximum can be used if it falls at least 10 beats/min below the abnormal level. Otherwise, the recommended training heart rate is 10 beats/min less than that associated with the abnormality. Guidelines for electrocardiographic monitoring Role in exercise training. Various recommendations exist about the number of ECG-monitored sessions that are necessary and reasonable in an exercise training program. Some programs use as few as six sessions, with progression in mode and intensity of the exercise during these periods.95 Others have used as many as 36 sessions of ECG monitoring. The fewest possible sessions should be used, and it is recommended that the classification suggested here be used as a guideline for the number of follow-ups required. (See Table 15.) Individuals who are class A (apparently healthy) do not require ECG-monitored sessions as the general guidelines are adequate. Class B individuals should be monitored and supervised until they understand their desirable activity levels (usually 6-12 sessions). Class C and D individuals should be medically supervised with ECG monitoring until they understand the level of activity that is safe and the medical team determines that the exercise is well tolerated and effective. Usually 6-12 sessions or more are needed. Monitored cardiac rehabilitation. Monitoring sessions should ideally be performed with continuous ECG monitoring by either hardwired apparatus or telemetry. The sessions should be conducted by personnel who understand the exercise principles involved and have a basic knowledge of electrocardiography. The sessions should also be supervised by either a physician or a nurse trained in emergency CPR. CPR capability can be demonstrated by completion of an AHA-sponsored course in advanced cardiac life support. Standing orders for management of a complication should be immediately available. Monitored sessions should also include symptom assessment by the staff, systolic blood pressure recording, rating of perceived exertion, and instructions to patients about selection and proper use of exercise equipment. The ECG-monitored sessions should include staff-taught sessions on adapting to different modes and progressions of exercise. Home-monitored programs. The use of transtelephonic ECG monitoring at home has been suggested as a substitute for outpatient visits to the clinic.96,97 Such programs have the disadvantage of lacking immediately available emergency medical care, but the advantage of no required clinic visit. The equipment is also not generally available, but these programs would be particularly useful in following up high-risk cases in which clinics are not readily available. Unmonitored home programs. In the first 1-2 weeks after discharge from the hospital after myocardial infarction, individuals may walk at a slow, regular pace with increasing duration, starting with 10- minute periods and working up to 1 hour. Such activity need not be supervised. Unmonitored exercise98 can also be used for conditioning after the individual has recovered from the myocardial infarction (2 weeks or more after hospital discharge) or in other cases of stable CAD, although medically supervised and monitored exercise is preferred. If cardiac rehabilitation facilities are not available, activity guidelines can still be provided to cardiac patients, and they should be encouraged to exercise. Activity should be restricted to walking (ordinary walking, not race walking) or equivalent activities. If individuals carefully watch for signs of intolerance and are attentive to heart rate and rating of perceived exertion, this activity level is considered safe. Walking is a safe, low-impact, controllable exercise that in the majority of cases generates an intensity that is 50-70% of Vo2 max It is recommended that activity be monitored if possible and prescribed from the exercise test results. However, if monitoring is not available, an activity

32 TABLE 16. Screening Process for Medically Supervised Programs for High-Risk Patients Consent of attending physician Stable clinical course Exercise test with current medications (for prescription) Patient's assurance of willingness to accept responsibility for higher risk and to follow instructions for modifying risk Exercise prescription with electrocardiographic monitoring at beginning and for change in activity levels to ensure activity is well tolerated and to define desirable levels of exercise other than walking can be prescribed, provided the intensity is similar to walking and that it is dynamic (as opposed to static). Range-of-motion exercises and light calisthenics can also be performed in an unmonitored setting. Activities are considered safe and appropriate if they meet the criterion of moderate intensity as perceived by the physician or judged by an exercise test. A useful guide to moderate (or less) activity is found in Table 14. It is permissible for individuals to participate in physical training classes if they carefully follow recommended guidelines for unmonitored exercise. In some cases, classes are desirable because of the camaraderie. Types of supervised programs Medically supervised group (moderate- to high-risk patients). These activity programs are needed to provide close medical supervision for individuals who are at particularly high risk for a complication associated with vigorous physical activity. Such individuals are largely from class D. These classes require careful medical supervision and surveillance to ensure that the activity is well tolerated. A physician should be immediately available (in the facility) for these classes, although the presence of a properly trained nurse in the exercise room is acceptable if the physician is not available. Training programs should be medically supervised until low risk of activity has been established. All individuals entering these programs should be screened as described in Table 16. The program should provide staff, space, equipment, and facilities. (See Table 17.) Medically supervised group (low-risk patients). Lowrisk patients (classes B and C) benefit from medically supervised programs because vigorous exercise can be conducted more safely and the group dynamics often help patients to comply with good health behaviors. Immediate medical supervision of low-risk patients can be provided by a well-trained nurse working under a physician's standard orders. The qualifications of the physician may vary, but experience in internal medicine and cardiovascular disease and treatment of patients with heart disease is recommended. If medical supervision by a physician cannot be provided, the person supervising patients should have successfully completed an AHA-sponsored course in advanced cardiac life support and be Writing Group Exercise Standards 2317 TABLE 17. Basic Requirements for Medically Supervised Programs for Moderate- to High-Risk Patients Adequately ventilated and temperature-controlled space Capability to assess patients with blood pressure and electrocardiographic analysis ECG monitoring during initial sessions to ascertain desirable exercise levels Supervision by either a nurse or physician in the exercise room. If a physician is not present, he or she must be immediately available (in the facility) for consultation. Medically qualified staff (completion of an AHA-sponsored advanced cardiac life support course [or the equivalent] and a minimum of two staff members present who are trained in cardiopulmonary resuscitation) Appropriate drugs and equipment (emergency medications [as outlined in the AHA's Textbook ofadvanced Cardiac Life Support] and cardioverter/defibrillator) Standard orders for the nurse if physician is not immediately available Written procedures for the following: Identification of conditions needed to conduct session Management of problems that do not require hospitalization such as acute, well-tolerated arrhythmias and neuromuscular injuries Ruling out myocardial infarction and management of problems requiring hospitalization, including postresuscitation problems Management of cardiac arrest, including procedure for immediate treatment and transportation to hospital able to administer emergency medication. Welltrained cardiovascular nurses usually meet these criteria. All individuals entering these programs should be screened as outlined in Table 18. The program should provide the same basic requirements as for high-risk patients as detailed in Table 17. Nonmedically supervised group (low-rtisk patients). These programs consist of activities for patients who do not require medical supervision. They are desirable because group dynamics are helpful and because exercise professionals can assist the patients. Records. Cardiac rehabilitation instructors should maintain evaluation forms, records of progress in problem areas, daily logs, and careful documentation of complications in much the same way as clinic and hospital charts. Regular exercise testing. Exercise testing is important in all programs and should be performed at TABLE 18. Screening Process for Medically Supervised Programs for Low-Risk Patients Permission of patient's personal physician, who judges patient to be either NYHA functional class 1 or 2 Exercise test without severe ischemic changes or high-grade ventricular ectopy Willingness to accept responsibility for higher risk and to follow instructions for modifying risk Exercise prescription with electrocardiographic monitoring at beginning and for change in activity levels to ensure activity is well tolerated and to define desirable levels of exercise heart rates NYHA, New York Heart Association.

33 2318 Special Report Circulation Vol 82, No 6, December 1990 regular intervals, regardless of location or type of rehabilitation program. Once a year is adequate, although more frequent tests may be necessary if the patient's condition is uncertain. Key Point: Precautions and procedures for activity programs are outlined. Symptoms and signs, types of activity, techniques of activity prescription, guidelines for ECG monitoring, types of supervised programs, and requirements for exercise testing must all be considered. Activities and precautions are geared to the severity of the illness. Social service and vocational rehabilitation Helping the individual return to activities and a lifestyle that is as normal as possible is the focus of rehabilitation and requires close cooperation between the patient, physician, employer, and social service agencies. Decisions about long-term goals must be made early. These goals include issues of personal safety and an acceptable standard of living for the patient and productivity for the employer. Since few jobs require jogging, it is difficult to know how other types of heavy labor are related in terms of risk. The general concept of lifting no more than 20 pounds is poorly supported by facts, but it is thought that some lifting may be hazardous because of the risk of acute increase in afterload on the heart. Measuring heart rate and blood pressure response is helpful but is seldom possible because of the type of work involved. One of the most difficult tasks facing a physician is advising the patient to return to work. Heavy labor can increase afterload, increasing the risk of sudden cardiac arrest accordingly. It also poses a problem for employers who are liable for workmen's compensation if a complication of heart disease occurs on the job. Conversely, loss of employment (even with disability compensation) is a 'blow to prestige," undoubtedly increasing feelings of anxiety. If the patient is in a low-risk activity category (classes B and C) and exerts reasonable precautions, the probability of a complication is very small. Hence, such patients should be encouraged and helped to return to work. If the patient is in a high-risk category (class D), the case must be judged on its individual merits. Even so, many of these patients can return to work if the following guidelines are followed. * The patient should participate in an organized, medically supervised cardiac rehabilitation program to enhance strength and endurance and to provide surveillance and education during return to activity. * Assist devices should be used to limit the amount of lifting performed. * Good cardiovascular health should be maintained through risk factor reduction and regular medical follow-up. * If the patient is required to lift more than 20 pounds per load, lifting should be infrequent, take place in optimum environmental conditions, and spaced with rest periods to avoid cumulative effects. Arm training in cardiac rehabilitation programs may be particularly useful for individuals in this group. Social service and employer resources should be used to limit the amount of lifting as much as possible. Key Point: Assessment for employment potential should include the patient's illness and conditions of employment. Most patients can return to work with few precautions. Cooperation with the employer is essential for optimum return to work. The importance of risk factors It is important to encourage simultaneous use of nutrition and good health behavior counseling for all individuals undergoing cardiac rehabilitation. Physical activity should be regarded as a part but not the whole of cardiac rehabilitation. Sexual activity Sexual activity is a moderate form of exercise for most individuals with CAD. Heart rates reach less than 120 beats/min, systolic blood pressure is under 170 mm Hg, and metabolic requirements are between 5 and 7 METs.99 There appears to be no particular benefit in altering positions or sexual customs. Exercise training can lessen the hemodynamic stress of sexual activity, but sexual activity contributes relatively little to the overall training program. The use of,-blockers and other drugs may impair sexual performance. The patient should be cautioned about such adverse reactions before leaving the hospital and encouraged to report them. An exercise test within 3 weeks after myocardial infarction, CABS, or PTCA may reassure both patient and spouse, as well as provide guidelines. The individual should resume sexual activity as he or she resumes other activities. In general, sexual activity should be deferred until activities such as walking and driving are resumed, usually about 2-4 weeks after returning home. Informed Consent for Exercise Training I want to participate in the exercise training program to improve my cardiovascular function. This program was recommended by my physician, Dr. I will have a clinical evaluation before I enter this exercise program. This evaluation will include a medical history and physical examination consisting of but not limited to ECG at rest and, in some instances, with effort, and measurements of heart rate and blood pressure. The purpose of this evaluation is to detect a condition indicating that I should not engage in this exercise training program. The program will follow an exercise prescription prepared by Dr. I understand that activities are designed to place a gradually increasing work load on the circulation in an attempt to improve its function. The reaction of the cardiovascular system to such activities cannot be predicted with complete accuracy. Certain changes may occur during or after exercise, including abnormalities of blood pressure or heart rate, ineffective heart function, and, possibly, in some instances, heart attacks or cardiac arrest.

34 Writing Group Exercise Standards 2319 I realize that it is necessary for me to promptly report symptoms or signs indicating any abnormality or distress to the exercise supervisor. I consent to administration of immediate resuscitation measures deemed advisable by the exercise supervisor. I have read the above and I understand it. My questions have been answered to my satisfaction. Patient - Physician Witness - Date Testing Arrhythmia avo2 difference Balke-type protocol Bruce-type protocol CAD Calories Exercise capacity Gender Isometric Isotonic J-junctional depression Kg Kpm MET Mo2 0.1 mv Predictive value PTCA Rating of perceived exertion Sensitivity Specificity ST depression Training Vo2 V02 max Training Aerobic Anaerobic Cardiac output Cardiovascular exercise Ejection fraction Exercise prescription Flexibility activity Medical supervision NYHA Occupational activity Strength activity Stroke volume Glossary Dysrhythmia or abnormal heart rhythm Arteriovenous oxygen difference Constant speed ( mph) variable grade treadmill exercise test Variable speed and grade treadmill exercise test (incremental speed and grade increase every 3 minutes) Coronary artery disease: Coronary heart disease, myocardial infarction, coronary artery bypass surgery, coronary angioplasty, and ischemia Kilocalorie: amount of energy required to raise temperature of 1 kg water by 1 C. Calories/min = METs x 3.5 x kg /200 Functional capacity, training or conditioning level, level of fitness Male or female Static exercise: muscle contraction with no movement Dynamic exercise: muscle contraction producing movement Depression of beginning of ST segment Kilogram: 1,000 g Kilopond or kilogram meter of work: 1 J (10 ergs) Metabolic equivalent (3.5 ml * kg min- 1 of oxygen uptake) Myocardial oxygen uptake 1 mm (provided calibration is set at 10 mm/mv) Percentage of those with or without disease who are identified correctly Percutaneous transluminal coronary angioplasty Borg scale of 6 to 20 or 1 to 10 Percentage of persons who are sick who will have a positive test Percentage of persons who are not sick who will have a negative test Horizontal or downsloping (0.10 mv for msec), measured from isoelectric PR level Physical activity, conditioning, leading to fitness Oxygen uptake Maximum oxygen uptake Exercise in which energy needed is provided by using oxygen inspired to combust metabolites Exercise in which energy needed exceeds oxidative processes and nonaerobic metabolism begins Volume of blood ejected from heart in liters per minute. Normal: 6 1/min at rest Predominantly dynamic exercise using large muscle groups Ratio of left ventricular stroke volume to end-diastolic volume (or percentage of end-diastolic volume ejected with each cardiac contraction). Normal: 60-75% Guidelines for exercise based on exercise testing. Includes frequency, duration, intensity, mode, and progression of exercise. Activity designed to enhance range of motion of joints Physician immediately available in the exercise facility (the presence of a properly trained nurse in the exercise room is acceptable if physician is not available in the exercise room). New York Heart Association classification: Class 1: Heart disease without symptoms Class 2: Heart disease with symptoms during ordinary activity Class 3: Heart disease with symptoms during less than ordinary activity Class 4: Heart disease with symptoms at rest On-the-job activity such as a job requiring lifting of loads of 20 pounds or more at least hourly throughout the day or constantly moving any size load from place to place without mechanized aid Muscular contraction against resistance designed to increase skeletal muscle strength Amount of blood ejection from heart with each contraction. Normal: ml at rest

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