Related Readings Fletcher, G. F., Balady, G. J., Amsterdam, E. A., Chaitman, B., Eckel, R., Fleg, J., et al. (2001). Exercise standards for testing and training: A statement for healthcare professionals from the American Heart Association. Circulation, 104(14), 1694-1740. [Free Full Text]
Graded exercise testing (GXT): extension of medical history and physical examination GXT been preliminary step in diagnosis of hemodynamically significant coronary artery disease (CAD) Primary diagnostic criteria have been; ST-segment changes on the electrocardiogram (ECG) and their correlation with symptoms (angina pectoris, shortness of breath) consistent with exertional myocardial ischemia
The ST level is measured relative to the P-Q junction ST segment depression is the most common manifestation of exercise-induced myocardial ischemia
Several reasons for conducting a GXT before assuming risk of conducting an exercise test, one must be certain that indications for the test are adequate Dictate the relative criteria for terminating the test are judged and how the test results are evaluated For example, attitude when conducting GXT on healthy individual at risk for CVD different than a patient who presents clinically
Clinically Accepted Reasons for Performing Graded Exercise Testing Extension of the history and physical allows physician to examine patient during symptoms Evaluate exertional discomfort Chest discomfort Dyspnea Leg discomfort Palpitations Cerebral symptoms Evaluate the presence of occult coronary artery disease Risk stratification in patients with known cardiovascular disease Follow-up of therapy Exercise prescription ACC/AHA 2002, Circulation 106: 1883-1892
Several things must be considered; indications and contraindications to exercise testing type of ergometer endpoint of exercise test protocol and safety considerations Both absolute and relative contraindications person conducting test should go over informed consent immediately before test even if patient has already signed important to tell patient what likely to feel during the test
Absolute Rest Acute MI (within 2 days) High-risk unstable angina Uncontrolled cardiac arrhythmias Active endocarditis Symptomatic severe aortic stenosis Symptomatic heart failure Pulmonary infarction Acute myocarditis or pericarditis Inability to obtain consent Relative* Left main coronary stenosis Stenotic valvular heart disease Electrolyte abnormalities Tachyarrhythmias Bradyarrhythmias Atrial fibrillation Hypertrophic cardiomyopathy High-degree AV block * Relative contraindications can be superseded if benefits outweigh risks of exercise ACC/AHA 2002, Circulation 106: 1883-1892
Summary of Studies Using Exercise ECG Testing in Chest Pain Centres Source: ACC/AHA Guideline Update for Exercise Testing: Summary Article. Gibbons et al. 2002, 106:1883-1892 Circulation
Perform resting ECG before beginning stress test 1. identify contraindications for testing 2. make sure resting ECG is normal to allow interpretation of changes that might occur during exercise test
1. Initial level of exertion should be submaximal 2. Increments between stages should be comparatively small and of consistent size 3. Protocol should allow estimation of exercise capacity 4. Test should be efficient of patient and physician time
Protocols suitable for clinical evaluation should include; low-intensity warm-up phase, progressive, continuous exercise, demand (for oxygen) is elevated to a desired level total duration of 8-12 minutes Typically sub-maximal, terminating (unless otherwise indicated) at predetermined % of estimated MHR (~75-80%) Bruce protocol (Bruce et al. 1973) Modified Bruce (Lerman et al. 1976) Astrand protocol (Astrand 1965)
Bruce treadmill protocol most widely used clinical setting for asymptomatic or high risk patients meets general principles criteria Protocol begins at 2.7 km/hr /10% grade, increases by 1.3 km/h / 2% grade every 3mins
Heyward VH. 2006, Advanced Fitness Assessment and Exercise Prescription, 5/e, Champaign, IL: Human Kinetics.
Bruce Treadmill Protocol for VO 2max Test Time Bruce Speed Grade METs min:sec Stage (km/hr) (%) Walk 0:00-3:00 1 2.7 10 5 3:00-6:00 2 4.0 12 7 Jog/Run 6:00-9:00 3 5.5 14 10 9:00-12:00 4 6.8 16 13 Run 12:00-15:00 5 8.0 18 16 15:00-18:00 6 8.0 20 18 18:00-21:00 7 9.7 22 22 Recovery (Jog/Walk) 0:00-2:00 2 4.0 12 7 Adapted from ASCM 2005, Health related physical fitness assessment manual. Lippincott, Williams and Wilkins, New York, NY
Adapted from ASCM 2005, Health related physical fitness assessment manual. Lippincott, Williams and Wilkins, New York, NY Estimate VO 2max calculated from total exercise duration using the appropriate regression formula: Men: VO 2max = 2.94 Time (min) + 7.65 Young Men: VO 2max = 2.94 Time (min) + 3.91 Women: VO 2max = 2.94 Time (min) + 3.74 Working example: female client exercise duration 7:52 (52/60 = 0.86) VO 2max = 2.94 (7.86) + 3.74 = 26.8 ml kg -1 min -1
Advantages 1. Allows the patient to reach high levels of exertion and is especially appropriate for active patients 2. Requires a shorter duration of testing than other protocols because of the rapid increase in workload Disadvantages 1. Patients must adjust to the change in both slope and speed at each stage 2. Most patients need to be running by stage 4 or 5
Protocol ideal only for younger individuals normal exercise capacity and a good ability to communicate with the physician conducting the test Less than optimal for older, more debilitated patients relatively high starting aerobic requirements and the large increases between stages encourage extensive handrail support, compromises accurate evaluation of exercise capacity
Naughton protocol is often recommended maintains nearly constant treadmill speed (3.2 4.8 km/h), and increase workload increments in grade (between 2 and 5%) every 2 min (Naughton et al. 1964) When testing athletes increments in workload should be adapted in accordance with level of fitness treadmill speed and elevation should begin at 5 km/h and 0% grade, increase by 1.6 km/h and 2% every 2 min. running protocol negates accurate ECG and blood pressure recording s, patient s health must be ascertained beforehand
Heyward VH. 2006, Advanced Fitness Assessment and Exercise Prescription, 5/e, Champaign, IL: Human Kinetics.
Relation of METs to stages in the various testing protocols. Functional class refers to New York Heart Association class; Abbreviations: kpm = kilopond-meters; MPH = miles per hour; %GR = percent grade. Source: AHA 2001, Circulation 104: 1694-1740
Test should be continued until the clinical question that prompted GXT has been answered arbitrary termination criteria based on a predetermined workload or percent of the age-predicted HR difficult to justify Considering the importance of ex capacity as prognostic marker, failure to take patient to fatigue or symptom or sign limitation is hard to defend after abnormal findings have been documented, little justification for continuation of test
ST-segment elevation (>1.0 mm) in leads without Q waves (other than V1 or avr) Drop in SBP >10 mmhg, despite increase in workload, when accompanied by any other evidence of ischemia Moderate-to-severe angina (grade 3 to 4) CNS symptoms (eg, ataxia, dizziness, or near syncope) Signs of poor perfusion (cyanosis or pallor) Sustained ventricular tachycardia Technical difficulties monitoring ECG or systolic blood pressure Subject s request to stop Source: ACC/AHA Guideline Update for Exercise Testing: Summary Article. Gibbons et al. 2002, 106:1883-1892 Circulation
ST or QRS changes such as excessive ST displacement (horizontal or downsloping of >2 mm) or marked axis shift Drop in SPB >10 mmhg despite increase in workload, in the absence of other evidence of ischemia Increasing chest pain Fatigue, shortness of breath, wheezing, leg cramps, Arrhythmias other than sustained ventricular tachycardia Hypertensive response (systolic blood pressure >250 mm Hg and/or diastolic blood pressure >115 mm Hg). Development of bundle-branch block that cannot be distinguished from ventricular tachycardia Source: ACC/AHA Guideline Update for Exercise Testing: Summary Article. Gibbons et al. 2002, 106:1883-1892 Circulation
5 factors must be considered during the interpretation 1. Clinical responses 2. ECG responses 3. Exercise capacity 4. Hemodynamic responses 5. Integrated response, as reflected by exercise test scores
Clinical response to exercise test must be evaluated in terms of the clinical context reflected by pretest likelihood of ischemic CVD that might have been the indication for the exercise test Fewer symptoms observed during exercise testing than during spontaneous exercise influence of warm-up during exercise testing (Maybaum et al. 1996, Am J Cardiol 78: 1087-1091) If so, why would this be the case?
Normal response to progressive treadmill exercise in healthy subjects Source: AHA 2001, Circulation 104: 1694-1740
Normal ECG has three clearly recognisable waves which accompany each cardiac cycle P Wave = atrial depolarisation QRS Complex = ventricular depolarisation T wave = indicates ventricular repolarisation
Sinus rhythm Tachycardia Bradycardia Arrhythmia
ECG changes in ST segment: Benchmark exercise-induced ischemia usually a lead with greatest degree of ST change, surrounded by leads with progressively less ST change ST-segment depression, changes that occur early during ex test, evident in multiple leads, persist into recovery predictive of either severe CAD or multivessel disease
ST segment depression common manifestation of exercise-induced myocardial ischemia. ST segment elevation during exercise localises the site of severe transient ischemia resulting from significant proximal disease or spasm. ECG abnormalities at rest, (T wave inversion; ST segment depression) may return to normal during attacks of angina and during exercise in some subjects with ischemic heart disease.
Dysrhythmias that increase in frequency or complexity with progressive exercise; 1. associated with ischemia 2. associated with hemodynamic instability thought to be more malignant than isolated dysrhythmias high-grade dysrhythmias occurring during exercise or recovery associated with poor long term prognosis
Exercise-induced arrhythmias generated by enhanced sympathetic tone, increased myocardial oxygen demand, or both. The period immediately after exercise is particularly dangerous because of the high catecholamine levels that are associated with generalized vasodilation
High VO 2max inferred to predict relatively high Q infers absence of serious limitations left ventricular function Importance of ex capacity relative to prognosis of patients with CVD (Myers et al. 2002, N Engl J Med 346: 793-801) significant issue relative to ex capacity is imprecision of estimating ex capacity from ex performance error in estimating ex capacity from prediction equations is about 1 MET unimportant (<10% error) in young, healthy individuals more significant (15 25% error) in individuals with reduced exercise capacities
Ex capacity understood in terms of age- and gender-predicted norms VO 2max below 20 th percentile for age and sex, often indicative of sedentary lifestyle, associated with increased risk of death (Blair et al. 1995, JAMA 273: 2395-2401) data based on physically active individuals, which probably should be the interpretative norm (Morris et al. 1993, J Am Coll Cardiol 22: 175-182; ACSM 2006 GETP 7/e)
Evaluate momentary safety during exercise testing abnormalities in pattern/magnitude of SBP response recognised for prognostic significance patients who cannot achieve adequate ex HR response have unfavorable prognosis beyond accounted for by symptoms or ECG changes Chronotropic incompetence Chronotropic index
Chronotropic incompetence: failure to achieve 85% of the age-predicted heart rate in patients with no pharmacologic reason to have limitation in HR response magnitude of prognostic value of poor HR response is as powerful as is an exercise-induced myocardial perfusion deficit Abnormal chronotropic response provides information that is independent of myocardial perfusion combination of perfusion deficit and abnormal chronotropic index provides worse prognosis than either abnormality alone regression analysis: failure to HR by 12bpm during 1 st associated with death during follow-up period min of recovery strongly failure of HR to recover related to inability to reassert vagal control over HR, predisposition to arrhythmias
Use of ex test scores combine both favorable and unfavorable ex test results into a single prognostically useful term Duke Index (Mark et al. 1991, N Engl J Med 325: 849-853) balances favorable result (exercise capacity) against two unfavorable results (ST-depression magnitude and presence and severity of angina pectoris) calculated score related to well-defined 5-year survival rate allows categorisation of patient (low-, moderate-, and high-risk subgroups) used in combination with simple hemodynamic findings such as abnormal pattern of HR recovery or combination of abnormal chronotropic index or an abnormal HR recovery
Duke Nomogram Duke Nomogram uses five steps to estimate prognosis for a given individual from the parameters of the Duke score 1. Observed amount of ST-depression marked on ST-segment deviation line 2. Observed degree of angina is marked on line for angina, and these two points are connected 3. Point where line intersects the ischemia reading line is noted 4. Observed exercise tolerance is marked on ex capacity line 5. Mark on the ischemia reading line is connected to the mark on the exercise capacity line, and the estimated 5-year survival or average annual mortality rate is read from the point at which this line intersects the prognosis scale
Sample nomogram shows testing results of 55 yro male sheetmetal worker with atypical chest pain patient reached 7METsbefore the test was stopped because of exercise-limiting angina. 2mm horizontal ST-segment depression at max exercise. Predicted annual cardiovascular mortality for this patient 4.0%, which is high.
Apparently independent information gained from pattern of increase in HR during exercise majority of healthy individuals, rate of increase in HR negatively accelerated at exercise intensities above the second ventilatory threshold 5% healthy individuals and high % of individuals with CVD, HR performance curve positively accelerated increase in the rate of HR is a method of defending Q in individuals who have large decreases in stroke volume at high exercise intensities
SBP normally negatively accelerated manner during incremental exercise magnitude of increase ~5 10mmHg per MET, minimal increase of 10mmHg from rest to maximal exercise considered normal Peak SBP > 250 mmhg or > 140 mmhg considered hypertensive response somewhat predictive of future resting hypertension In patients with Q limitations, inappropriately slow increase BP or a SBP decrease midway through Extest
SBP decrease below resting value or >10 mmhg after preliminary increase (in presence of other indices of ischemia) grossly abnormal sufficient reason to stop the test immediately DBP difficult to measure with accuracy during GXT increase >10 mmhg considered to be abnormal finding, as is an increase to more than 115mmHg consistent with exertional ischemia Post-exercise SBP normally decreases promptly 3-min post-ex SBP should be < 90% of SBP at peak exercise 3-min post-ex SBP should < SBP measured 1 min post-ex
Major advantage of measuring gas exchange is more accurate measurement of functional capacity also allow the determination of ventilatory threshold may be useful in defining prognosis
Much information in simple incremental GXT data more important in terms of defining prognosis than making specific diagnosis of obstructive CAD central feature appears to be functional exercise capacity Prognostic impression gained from exercise capacity typically balanced by ECG or symptomatic evidence of exertional myocardial ischemia relationship well expressed in exercise test scores such as the Duke Index Hemodynamic responses shown to be very powerful prognostic markers
Key Concept Exercise testing is an extension of the history and physical designed to allow the physician to evaluate the patient in circumstances likely to be provocative of the signs or symptoms consistent with exertional myocardial ischemia or other manifestations of CVD