PREOPERATIVE ASSESSMENT OF THE PATIENT WITH CARDIAC DISEASE

Transcription

1 CHAPTER 7 V O L U M E T H I R T Y - T H R E E PREOPERATIVE ASSESSMENT OF THE PATIENT WITH CARDIAC DISEASE LEE A. FLEISHER, M.D. ROBERT D. DRIPPS PROFESSOR AND CHAIR DEPARTMENT OF ANESTHESIOLOGY AND CRTICAL CARE PROFESSOR OF MEDICINE UNIVERSITY OF PENNSYLVANIA SCHOOL OF MEDICINE PHILADELPHIA, PENNSYLVANIA EDITOR: ALAN JAY SCHWARTZ, M.D., M.S.ED. ASSOCIATE EDITORS: M. JANE MATJASKO, M.D. JEFFREY B. GROSS, M.D. The American Society of Anesthesiologists, Inc.

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3 Preoperative Assessment of the Patient with Cardiac Disease Lee A. Fleisher, M.D. Robert D. Dripps Professor and Chair Department of Anesthesiology and Critical Care Professor of Medicine University of Pennsylvania School of Medicine Philadelphia, Pennsylvania Despite the emphasis over the last 2 decades on the role of preoperative cardiac testing before noncardiac surgery, there continues to be a paucity of evidence to demonstrate the benefits of a testing paradigm. Much of the research to date has focused on defining the predictive value of a number of diagnostic tests and the association between coronary revascularization and perioperative cardiac morbidity. More recently, there is increasing emphasis on the value of perioperative pharmacologic management. A basic tenet in preoperative evaluation is that information regarding the extent and stability of disease will affect patient management and lead to improved outcome. In the case of cardiovascular disease, the preoperative evaluation attempts to define the extent of coronary artery disease and the left ventricular function. This Refresher Course uses the American College of Cardiology/American Heart Association (ACC/AHA) Guidelines on Perioperative Cardiovascular Evaluation for Noncardiac Surgery as the basis for discussing the optimal care for the high-risk patient. 1 Several authors have suggested that extensive evaluation is no longer necessary in an era of low cardiac morbidity. They argue that improvements in intra- and postoperative care obviate the need for an extensive evaluation, particularly with the use of perioperative pharmacologic therapy. In addition, a recently published randomized trial (CARP) suggests that coronary revascularization is of no benefit before major vascular surgery in patients with coronary disease exclusive of left main disease. 2 However, it is important to recognize that these interventions were not studied in those patients with the highest risk, that is, those with extensive symptomatic disease. Therefore, it remains important to identify those with symptomatic and potentially highgrade disease. Cardiac Risk Indices Since the original manuscript by Goldman and colleagues in 1977 describing a Cardiac Risk Index, multiple investigators have validated various clinical risk indices for their ability to predict perioperative cardiac complications. The Goldman Cardiac Risk Index originally defined nine factors, each of which was given a weight or number of points. The cardiac risk index has been validated in large populations of diverse types of noncardiac surgery but does not appear as robust in selected populations of patients undergoing major vascular surgery. Detsky et al. modified the cardiac risk index, adding Based in part on the ASA Refresher Course Lecture 2004, with permission. 79

4 80 FLEISHER factors such as major vascular surgery and angina. The most recent index was developed in a study of 4,315 patients aged 50 years or greater undergoing elective major noncardiac procedures in a tertiary-care teaching hospital. 3 Six independent predictors of complications were identified and included in a Revised Cardiac Risk Index: high-risk type of surgery, history of ischemic heart disease, history of congestive heart failure, history of cerebrovascular disease, preoperative treatment with insulin, and preoperative serum creatinine >2.0 mg/day, with increasing cardiac complication rates noted with increasing number of risk factors. A primary issue with all of these indices from the anesthesiologist s perspective is that a simple estimate of risk does not help in refining perioperative management, but may provide information to assess the probability of complications. In contrast, the anesthesiologist is most concerned with defining the cardiovascular risk factors and symptoms or signs of unstable cardiac disease states such as myocardial ischemia, congestive heart failure, valvular heart disease, and significant cardiac arrhythmias. Therefore, the calculation of a simple score does not provide sufficient information for the anesthesiologist to appropriately modify perioperative management. The preoperative evaluation should help define those patients who require perioperative interventions (Table 1). Clinical Risk Factors A thorough history should focus on cardiovascular risk factors and symptoms or signs of unstable cardiac disease states such as myocardial ischemia with minimal exertion, active congestive heart failure, symptomatic valvular heart disease, and significant cardiac arrhythmias (Table 2). In patients with symptomatic coronary disease, preoperative evaluation may lead to the recognition of a change in the frequency or pattern of anginal symptoms. Symptoms of cardiovascular disease should be carefully determined, especially characteristics of chest pain, if present. The presence of unstable angina has been associated with a high perioperative risk of myocardial infarction (MI). 4 The preoperative evaluation can impact on both a patient s short- and long-term health by instituting treatment of unstable angina. The patient with stable angina represents a continuum from mild angina with extreme exertion to dyspnea with angina after walking up a few stairs. The patient who only manifests angina after strenuous exercise does not demonstrate signs of left ventricular dysfunction and would not be a candidate for changes in management. In contrast, a patient with dyspnea on mild exertion would be at high risk for developing perioperative ventricular dysfunction, myocardial ischemia, and possible MI. These patients TABLE 1. Perioperative Interventions Based on Preoperative Cardiac Evaluation Decision to forego surgery Modification of surgical procedure Delay case for treatment of unstable symptoms Modification of intraoperative monitors Modification of perioperative medical therapy Initiation of beta-blockers, statins, alpha-2 agonists Modification of postoperative monitoring (e.g., intensive care unit) Coronary revascularization before noncardiac surgery Modification of location of care

5 PREOPERATIVE CARDIAC EVALUATION BEFORE NONCARDIAC SURGERY 81 TABLE 2. Clinical Predictors of Increased Perioperative Cardiovascular Risk (Myocardial Infarction, Congestive Heart Failure, Death) Major Unstable coronary syndromes Recent myocardial infarction* with evidence of important ischemic risk or clinical symptoms or noninvasive study Unstable or severe angina (Canadian class III or IV) Decompensated congestive heart failure Significant arrhythmias High-grade atrioventricular block Symptomatic ventricular arrhythmias in the presence of underlying heart disease Supraventricular arrhythmias with uncontrolled ventricular rate Severe valvular disease Intermediate Mild angina pectoris (Canadian class I or II) Prior myocardial infarction by history or pathologic Q waves Compensated or prior congestive heart failure Diabetes mellitus Chronic renal insufficiency Minor Advanced age Abnormal electrocardiogram (left ventricular hypertrophy, left bundle branch block, ST-T abnormalities) Rhythm other than sinus (e.g., atrial fibrillation) Low functional capacity (e.g., inability to climb one flight of stairs with a bag of groceries) History of stroke Uncontrolled systemic hypertension *The American College of Cardiology National Database Library defines recent myocardial infarction as greater than 7 days but less than or equal to 1 month (30 days). May include stable angina in patients who are unusually sedentary. Campeau L. Grading of angina pectoris. Circulation. 1976; 54: Reproduced with permission from Eagle KA, Berger PB, Calkins H, et al.: ACC/AHA guideline update for perioperative cardiovascular evaluation for noncardiac surgery Executive summary: A report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Committee to Update the 1996 Guidelines on Perioperative Cardiovascular Evaluation for Noncardiac Surgery). J Am Coll Cardiol 2002; 39: have an extremely high probability of having extensive coronary artery disease, and additional monitoring or cardiovascular testing should be contemplated, depending on the surgical procedure and institutional factors. In virtually all studies, the presence of active congestive heart failure preoperatively has been associated with an increased incidence of perioperative cardiac morbidity. Stabilization of ventricular function and treatment for pulmonary congestion is prudent before elective surgery. Also, it is important to determine the etiology of the left heart failure. Congestive symptoms may be the result of nonischemic cardiomyopathy or mitral or aortic valvular insufficiency and/or stenosis. Because the type of perioperative monitoring and treatments would be different, clarifying the cause of cardiac congestion is important. Patients with a prior MI have coronary artery disease, although a small group of patients may sustain an MI from a nonatherosclerotic mechanism. Traditionally, risk assessment for noncardiac surgery was based on the time interval between the MI and surgery. Multiple studies have demonstrated an increased incidence of reinfarction if the MI was within 6 months of surgery. With improvements in perioperative care, this difference has decreased. 5

6 82 FLEISHER However, the importance of the intervening time interval may no longer be valid in the current era of thrombolytics, angioplasty, and risk stratification after an acute MI. Although many patients with an MI may continue to have myocardium at risk for subsequent ischemia and infarction, other patients may have their critical coronary stenosis either totally occluded or widely patent. Therefore, patients should be evaluated from the perspective of their risk for ongoing ischemia. The ACC/AHA Guidelines on Perioperative Evaluation of the Cardiac Patient undergoing Noncardiac Surgery has advocated the use of an MI <30 days before surgery as the group at highest risk, whereas after that period, risk stratification is based on the presentation of disease and exercise tolerance. Patients at Risk for Coronary Artery Disease For those patients without overt symptoms or history, the probability of coronary artery disease (CAD) varies with the type and number of atherosclerotic risk factors present. Peripheral arterial disease has been shown to be associated with CAD in multiple studies. Hertzer and colleagues studied 1,000 consecutive patients scheduled for major vascular surgery and found that approximately 60% of patients had at least one coronary artery with a critical stenosis. 6 Diabetes mellitus is common in the elderly and represents a disease that impacts multiple organ systems. Complications of diabetes mellitus are frequently the cause of urgent or emergent surgery, especially in the elderly. Diabetes accelerates the progression of atherosclerosis, which can frequently be silent in nature. Diabetics have a high incidence of both silent MI and myocardial ischemia. Diabetes is an independent risk factor for perioperative cardiac morbidity. 3 In attempting to determine the degree of this increased probability, the length of the disease and other associated end-organ dysfunction should be taken into account, including autonomic neuropathy. Hypertension has also been associated with an increased incidence of silent myocardial ischemia and infarction. Those hypertensive patients with left ventricular hypertrophy and who are undergoing noncardiac surgery are at a higher perioperative risk than nonhypertensive patients. There is a great deal of debate regarding a trigger to delay or cancel a surgical procedure in a patient with poorly or untreated hypertension. Although Goldman and Caldera suggested that a case should be delayed if the diastolic pressure is greater than 110 mm Hg, they demonstrated no major morbidity in this small cohort of individuals in their study. 7 In the absence of end-organ changes such as renal insufficiency or left ventricular hypertrophy with strain, it would seem appropriate to proceed with surgery. A recent randomized trial of treated hypertensive patients without known CAD who presented the morning of surgery with an elevated diastolic blood pressure was unable to demonstrate any difference in outcome between those who were actively treated versus those in whom surgery was delayed. 8 In contrast, a patient with a markedly elevated blood pressure and the new onset of a headache should have surgery delayed for further evaluation and potential treatment. Several other risk factors have been used to suggest an increased probability of CAD. These include the atherosclerotic processes associated with tobacco use and hypercholesterolemia. Based on work by Lee et al., chronic renal insufficiency is also a risk factor for perioperative cardiac morbidity. 3 Although these risk factors increase the probability of developing CAD, they have not been shown to increase perioperative risk. When attempting to determine the overall probability of disease, the number and severity of the risk factors are important.

7 PREOPERATIVE CARDIAC EVALUATION BEFORE NONCARDIAC SURGERY 83 Importance of Surgical Procedure The surgical procedure influences the extent of the preoperative evaluation required by determining the potential range of changes in perioperative management. For example, coronary revascularization may be beneficial for procedures associated with a high incidence of morbidity and mortality, but not those associated with a low incidence, as described subsequently. There is little hard data to define the surgery-specific incidence of complications. It is known that peripheral procedures such as those included in a study of ambulatory surgery completed at the Mayo Clinic are associated with an extremely low incidence of morbidity and mortality. 9 Similarly, major vascular procedures are among those with the highest incidence of complications, with a similar incidence documented for infrainguinal and aortic surgery. Eagle et al. published data on the incidence of perioperative MI and mortality by procedure for patients enrolled in the Coronary Artery Surgery Study (CASS). 10 They determined the overall risk of perioperative morbidity in patients with known CAD on medical treatment, and the potential reduced rate of perioperative morbidity in those patients who had prior coronary artery bypass grafting (CABG). High-risk procedures for which CABG reduced the risk of noncardiac surgery compared with medical therapy include major vascular, abdominal, thoracic, and orthopedic surgery. The ACC/AHA Guidelines defined three tiers of surgical stress based on composite cardiac events rates, which are shown in Table 3. Importance of Exercise Tolerance Exercise tolerance is one of the most important determinants of perioperative risk and the need for invasive monitoring. Excellent exercise tolerance, even in patients TABLE 3. High Intermediate Low Cardiac Risk* Stratification for Noncardiac Surgical Procedures (Reported cardiac risk often >5%) Emergent major operations, particularly in the elderly Aortic and other major vascular Peripheral vascular Anticipated prolonged surgical procedures associated with large fluid shifts and/or blood loss (Reported cardiac risk generally <5%) Carotid endarterectomy Head and neck Intraperitoneal and intrathoracic Orthopedic Prostate (Reported cardiac risk generally <1%) Endoscopic procedures Superficial procedure Cataract Breast *Combined incidence of cardiac death and nonfatal myocardial infarction. Do not generally require further preoperative cardiac testing. Reproduced with permission from Eagle KA, Berger PB, Calkins H, et al.: ACC/AHA guideline update for perioperative cardiovascular evaluation for noncardiac surgery Executive summary: A report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Committee to Update the 1996 Guidelines on Perioperative Cardiovascular Evaluation for Noncardiac Surgery). J Am Coll Cardiol 2002; 39:

8 84 FLEISHER with stable angina, suggests that the myocardium can be stressed without becoming dysfunctional. If a patient can walk a mile without becoming short of breath, then the probability of extensive CAD is small. Alternatively, if patients become dyspneic associated with chest pain during minimal exertion, then the probability of extensive CAD is high. Reilly and colleagues demonstrated that the likelihood of a serious complication occurring was inversely related to the number of blocks that could be walked or flights of stairs that could be climbed. 11 Exercise tolerance can be assessed with formal treadmill testing or with a questionnaire that assesses activities of daily living (Table 4). Approach to the Patient The algorithm to determine the need for testing proposed by the ACC/AHA Task Force is based on available evidence and expert opinion, and integrates clinical history, surgery specific risk, and exercise tolerance (Fig. 1). 1 First, the clinician must evaluate the urgency of the surgery and the appropriateness of a formal preoperative assessment. Next, determine if the patient has undergone a previous revascularization procedure or coronary evaluation. Those patients with unstable coronary syndromes should be identified and appropriate treatment instituted. Finally, the decision to undergo further testing depends on the interaction of the clinical risk factors, surgeryspecific risk, and functional capacity. For patients at intermediate clinical risk, both exercise tolerance and the extent of the surgery are taken into account with regard to the need for further testing. No preoperative cardiovascular testing should be performed if the results will not change perioperative management. Therefore, although the algorithm may suggest testing, the recommendation is not for mandatory testing, but simply identification of a group that may benefit. Given the results of the CARP trial, these guidelines may soon be revised to suggest testing in an even smaller subset of patients. TABLE 4. Estimated Energy Requirement for Various Activities* 1 MET Can you take care of yourself? Eat, dress, or use the toilet? Walk indoors around the house? Walk a block or two on level ground at 2 to 3 mph or 3.2 to 4.8 km/h? Do light work around the house like dusting or washing dishes? 4 METs >10 METs Climb a flight of stairs or walk up a hill? Walk on level ground at 4 mph or 6.4 km/h? Run a short distance Do heavy work around the house like scrubbing floors or lifting or moving heavy furniture? Participate in moderate recreational activities like golf, bowling, dancing, doubles tennis, or throwing a baseball or football? Participate in strenuous sports like swimming, singles tennis, football, basketball, or skiing? MET = metabolic equivalent. *Adapted from the Duke Activity Status Index and AHA Exercise Standards. Reproduced with permission from Eagle KA, Berger PB, Calkins H, et al.: ACC/AHA guideline update for perioperative cardiovascular evaluation for noncardiac surgery Executive summary: A report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Committee to Update the 1996 Guidelines on Perioperative Cardiovascular Evaluation for Noncardiac Surgery). J Am Coll Cardiol 2002; 39:

9 PREOPERATIVE CARDIAC EVALUATION BEFORE NONCARDIAC SURGERY 85 FIG. 1. The American Heart Association/American College of Cardiology Task Force on Perioperative Evaluation of Cardiac Patients undergoing Noncardiac Surgery has proposed an algorithm for decisions regarding the need for further evaluation. This represents one of multiple algorithms proposed in the literature. It is based on expert opinion and incorporates six steps. First, the clinician must evaluate the urgency of the surgery and the appropriateness of a formal preoperative assessment. Next, he or she must determine whether the patient has had a previous revascularization procedure or coronary evaluation. Those patients with unstable coronary syndromes should be identified, and appropriate treatment should be instituted. The decision to have further testing depends on the interaction of the clinical risk factors, surgery-specific risk, and functional capacity. Adapted with permission from Eagle KA, Berger PB, Calkins H, et al.: ACC/AHA guideline update for perioperative cardiovascular evaluation for noncardiac surgery Executive summary: A report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Committee to Update the 1996 Guidelines on Perioperative Cardiovascular Evaluation for Noncardiac Surgery). J Am Coll Cardiol 2002; 39:

10 86 FLEISHER Choice of Diagnostic Test There are multiple noninvasive diagnostic tests that have been proposed to evaluate the extent of CAD before noncardiac surgery. The exercise electrocardiogram has been the traditional method of evaluating individuals for the presence of CAD. It represents the least invasive and most cost-effective method of detecting ischemia, with a reasonable sensitivity (68% to 81%) and specificity (66% to 77%) for identifying CAD. Electrocardiographic signs of MI and clinical signs of left ventricular dysfunction are considered positive. However, as outlined here, patients with a good exercise tolerance will rarely benefit from further testing. A significant number of high-risk patients are either unable to exercise or have contraindications to exercise. Therefore, pharmacologic stress testing has become popular, particularly as a preoperative test in patients undergoing vascular surgery. Pharmacologic stress for the detection of CAD can be divided into two categories: 1) those that result in coronary artery vasodilation such as dipyridamole, and 2) those that increase myocardial oxygen demand such as dobutamine. The coronary artery vasodilators work by producing differential flows in normal coronary arteries when compared with those with a stenosis. Several authors have shown that the presence of a redistribution defect on dipyridamole thallium imaging in patients undergoing peripheral vascular surgery is predictive of postoperative cardiac events. To increase the predictive value of the test, several strategies have been suggested. Lung uptake, left ventricular cavity dilation, and redistribution defect size have all been shown to be predictive of subsequent morbidity. Dobutamine stress echocardiography has been suggested as the best preoperative test in several recent metaanalyses. The appearance of new or worsened regional wall motion abnormalities is considered a positive test. These represent areas at risk for myocardial ischemia. The advantage of this test is that it is a dynamic assessment of ventricular function. Dobutamine echocardiography has also been studied and was found to have among the best positive and negative predictive values. Poldermans et al. demonstrated that the group at greatest risk was those who demonstrated regional wall motion abnormalities at low heart rates. 12 Interventions for Patients with Documented Coronary Artery Disease Strategies to reduce the perioperative risk of noncardiac surgery have recently been reviewed. Eagle et al. studied more than 3,000 noncardiac surgeries in patients who were originally enrolled in CASS and compared the rate of perioperative cardiac morbidity and mortality in those patients in the surgical versus medical treatment arms. In those patients who survived CABG, the rate of perioperative MI was lower for intermediate- or high-risk surgeries but not low-risk surgeries. The current evidence does not support the use of percutaneous transluminal coronary angioplasty (PTCA) beyond established indications for nonoperative patients, because the incidence of perioperative complications does not appear to be reduced in those patients in whom PTCA was performed less than 90 days before surgery. 13 The results of a multicenter Veterans Administration Cooperative Study (CARP) addressing the value of prophylactic coronary revascularization before major vascular surgery have recently been reported. 14 Patients with risk factors underwent coronary angiography and

11 PREOPERATIVE CARDIAC EVALUATION BEFORE NONCARDIAC SURGERY 87 TABLE 5. Risks/Benefits Associated with Preoperative Testing and Coronary Revascularization Morbidity/mortality association with: Preoperative testing Coronary angiography Coronary revascularization Benefits of preoperative coronary revascularization Reduced complications after noncardiac surgery Long-term improvement were then randomized to coronary revascularization (CABG or PTCA) versus medical therapy, excluding those with left main disease. No difference in either perioperative or long-term (average 2.7 years) outcome was observed. Based on the prevailing evidence, the indications for CABG and PTCA are identical to those in the nonoperative setting, and simply performing coronary revascularization to get the patient through surgery is not indicated. Coronary stent placement may be a unique issue in that two studies suggest that a minimum of 2 weeks, but preferably 6 weeks, is required before the rate of perioperative complications is low (Table 5). 15 Drug-eluting stents may represent an additional risk over a prolonged period (up to 6 months) based on case reports. There is now a great deal of evidence to suggest that perioperative medical therapy can be optimized in those patients with CAD as a means of reducing perioperative cardiovascular complications. 16 Multiple studies have demonstrated improved outcome in patients given perioperative β-blockers, especially if heart rate is controlled. 17 The current ACC/AHA Guidelines advocate these agents based on level I data in patients previously on β-blockers and those with a positive stress test undergoing major vascular surgery. 1 The use of these agents in those without active CAD or undergoing less-invasive procedures is advocated as a level IIa recommendation. Based on these newer studies, β-blockers may not be effective if heart rate is not well controlled or in lower-risk patients. A study of 497 patients undergoing vascular surgery randomized to a fixed dose of metoprolol versus placebo demonstrated no difference in perioperative outcome. 18 A trial of metoprolol in diabetic patients undergoing a diverse group of surgical procedures was unable to demonstrate any difference in perioperative outcomes. Other pharmacologic agents have also been shown to improve perioperative cardiac outcome. α-2 agonists have been shown to improve both perioperative mortality and 6-month event-free survival. 19 Most recently, perioperative statins have been shown to improve cardiac outcome. 20 A multimodal approach to medical management should be taken in high-risk patients. Summary Preoperative evaluation should focus on identifying patients with symptomatic and asymptomatic CAD and the exercise capacity of the patient. The decision to perform further diagnostic evaluation depends on the interactions of patients and surgeryspecific factors, as well as exercise capacity, and should be reserved for those at moderate risk undergoing major or intermediate surgery with poor exercise capacity. The indications for coronary interventions are the same in the perioperative period as for the nonoperative setting.

12 88 FLEISHER References 1. Eagle KA, Berger PB, Calkins H, et al.: ACC/AHA guideline update for perioperative cardiovascular evaluation for noncardiac surgery Executive summary: A report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Committee to Update the 1996 Guidelines on Perioperative Cardiovascular Evaluation for Noncardiac Surgery). J Am Coll Cardiol 2002; 39: McFalls EO, Ward HB, Moritz TE, et al.: Coronary artery revascularization prior to major elective vascular surgery and long-term outcome: the Coronary Artery Revascularization Prophylaxis (CARP) trial. N Engl J Med 2004; 351: Lee TH, Marcantonio ER, Mangione CM, et al.: Derivation and prospective validation of a simple index for prediction of cardiac risk of major noncardiac surgery. Circulation 1999; 100: Shah KB, Kleinman BS, Rao T, et al.: Angina and other risk factors in patients with cardiac diseases undergoing noncardiac operations. Anesth Analg 1990; 70: Rivers SP, Scher LA, Gupta SK, Veith FJ: Safety of peripheral vascular surgery after recent acute myocardial infarction. J Vasc Surg 1990; 11:70 5; discussion Hertzer NR, Bevan EG, Young JR, et al.: Coronary artery disease in peripheral vascular patients: A classification of 1000 coronary angiograms and results of surgical management. Ann Surg 1984; 199: Goldman L, Caldera DL: Risks of general anesthesia and elective operation in the hypertensive patient. Anesthesiology 1979; 50: Weksler N, Klein M, Szendro G, et al.: The dilemma of immediate preoperative hypertension: To treat and operate, or to postpone surgery? J Clin Anesth 2003; 15: Warner MA, Shields SE, Chute CG: Major morbidity and mortality within 1 month of ambulatory surgery and anesthesia. JAMA 1993; 270: Eagle KA, Rihal CS, Mickel MC, et al.: Cardiac risk of noncardiac surgery: Influence of coronary disease and type of surgery in 3368 operations. CASS Investigators and University of Michigan Heart Care Program. Coronary Artery Surgery Study. Circulation 1997; 96: Reilly DF, McNeely MJ, Doerner D, et al.: Self-reported exercise tolerance and the risk of serious perioperative complications. Arch Intern Med 1999; 159: Poldermans D, Arnese M, Fioretti PM, et al.: Improved cardiac risk stratification in major vascular surgery with dobutamine atropine stress echocardiography. J Am Coll Cardiol 1995; 26: Posner KL, Van Norman GA, Chan V: Adverse cardiac outcomes after noncardiac surgery in patients with prior percutaneous transluminal coronary angioplasty. Anesth Analg 1999; 89: McFalls EO, Ward HB, Krupski WC, et al.: Prophylactic coronary artery revascularization for elective vascular surgery: Study design. Veterans Affairs Cooperative Study Group on Coronary Artery Revascularization Prophylaxis for Elective Vascular Surgery. Control Clin Trials 1999; 20: Wilson SH, Fasseas P, Orford JL, et al.: Clinical outcome of patients undergoing non-cardiac surgery in the two months following coronary stenting. J Am Coll Cardiol 2003; 42: Fleisher LA, Eagle KA: Clinical practice. Lowering cardiac risk in noncardiac surgery. N Engl J Med 2001; 345: Auerbach AD, Goldman L: Beta-blockers and reduction of cardiac events in noncardiac surgery: Scientific review. JAMA 2002; 287: Yang H, Raymer K, Butler R, et al.: Metoprolol after vascular surgery (MaVS) [Abstract]. Can J Anaesth Wallace AW, Galindez D, Salahieh A, et al.: Effect of clonidine on cardiovascular morbidity and mortality after noncardiac surgery. Anesthesiology 2004; 101: Durazzo AE, Machado FS, Ikeoka DT, et al.: Reduction in cardiovascular events after vascular surgery with atorvastatin: A randomized trial. J Vasc Surg 2004; 39:

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