PRO: Preoperative Stress Testing According to ACC/AHA Guidelines is a Valuable Triage Adjunct For High Risk Cadiac Patients Prior to Noncardiac Surgery

Kim A. Eagle, MD
Albion Walter Hewlett Professor of Medicine
University of Michigan Cardiovascular Center

The ACC/AHA guidelines on preoperative stress testing were published initially in 19961 and updated in 2002.2 The guidelines were endorsed by the Society of Cardiovascular Anesthesiologists as well. Following the guidelines, preoperative stress testing may be performed for a cardiac patient prior to high-risk non-cardiac surgery, if the patient has not had a recent favorable cardiac evaluation within two years or coronary revascularization within five years without intervening changes in symptomatology and if the patient has either a poor functional capacity or one or more intermediate clinical predictors. Poor functional capacity may be defined as inability to carry out four METS of activity without symptoms of cardiovascular compromise such as chest pain, shortness of breath or fatigue.3 Intermediate clinical predictors are history of myocardial infarction, compensated congestive heart failure, stable angina pectoris, insulin-dependent diabetes mellitus, or chronic renal insufficiency with serum creatinine 2 mg/dl.3 The guidelines were based on the available literature evidence as well as expert opinions and collective wisdom from the disciplines of cardiovascular anesthesiology, cardiology, surgery, and related fields.

The value of preoperative stress testing performed according to these guidelines is demonstrated by the fact that (a) stress testing identifies patients at higher risk, (b) the results of the testing can lead to therapeutic interventions that may alter the risk, and (c) the application of the guidelines leads to improvement of outcomes.

First then, does stress testing identify patients at higher risk? The answer is, of course, a resounding yes. Impaired exercise testing is certainly predictive of perioperative complications. In a retrospective review, patients who reported poor exercise tolerance (could not walk four blocks or climb two flights of stairs) were twice as likely to have perioperative complications from major noncardiac surgery as those with good exercise tolerance (20.4% vs. 10.4%, P < 0.001).3 An anaerobic threshold of <11 cc O2/min/kg during preoperative cardiopulmonary exercise testing marks a very high risk group for perioperative cardiovascular deaths.4 Exercise capacity and ischemic ECG changes on exercise ECG testing provide important information before major noncardiac surgery, with positive predictive values ranging from 10-20% and negative predictive values exceeding 95%. The value of the stress testing with pharmacological stress testing is high in patients who cannot perform reasonable exercise. In a meta-analysis of dipyridamole-thallium imaging (DTI) studies, Shaw et al. demonstrated that in vascular surgical patients, those with a negative test had a 3.16% cardiac event rate, whereas those with a fixed defect had a 11.41% event rate and those with a reversible defect without prophylactic revascularization had a 18.12% cardiac event rate.5 Similarly, among vascular patients who had a dobutamine stress echocardiography (DSE), those with no new wall motion abnormalities had a 0.37% cardiac event rate while those with new dyssynergy had a 26.3% cardiac event rate with no prophylactic coronary revascularization.5 Certainly, stress testing provides discriminating information about the cardiovascular risks of patients undergoing high-risk noncardiac surgery.

Second, can the results of stress testing lead to therapies which alter risks? In the aforementioned meta-analysis by Shaw et al.5 when new dyssynergy was discovered by DSE, coronary revascularization resulted in 0% cardiac event rate during subsequent vascular surgery. Revascularization after identification of reversible perfusion defects on DTI similarly resulted in a significant reduction in cardiac event rate (5.88% vs. 18.12%). In a review of the CASS (Coronary Artery Surgery Study) database, we have shown that prior successful revascularization by CABG led to reduction of mortality (1.7% vs. 3.3%, P=0.03) and MI (0.8% vs. 2.7%, P=0.002) in a subsequent major noncardiac surgery.6 In the BARI (Bypass Angioplasty Revascularization Investigation) trial, a prospective study comparing surgical and percutaneous coronary revascularization, the protection conferred by angioplasty was found to be similar to surgical revascularization.7 While Poldermans et al. have certainly demonstrated the benefit of perioperative beta-adrenergic blockade in vascular patients who had a positive preoperative DSE with a significant reduction in mortality and MI,8 the results of DSE can help identify those extremely high-risk patients who may not be adequately protected by perioperative beta-adrenergic blockade and therefore require other therapeutic and/or triage strategies.9

Third, implementation of the ACC/AHA guidelines has been shown to lead to a strategy of more selective stress testing and intervention, compared to without the guidelines. In a historical review of the frequency of testing before and after implementation of the guidelines, Froehlich et al. found in patients undergoing elective abdominal aortic surgery that the guidelines halved stress testing (47% vs. 88%, P < 0.001) and coronary angiography (11% vs. 24%, P < 0.05).10 The reduction in revascularization either by angioplasty or CABG was even more impressive: 2% vs 24%, P < 0.001. The reduction in testing and intervention was achieved without adversely affecting cardiovascular outcome: Mortality was 4% before and 3% after implementation and MI 7% beforehand and 3% afterwards. Cost of preoperative care was reduced six fold from $1,087 to $171.

In summary, the ACC/AHA guidelines represent the scientific evidence and collective wisdom of our specialties. Stress testing performed according to the guidelines is able to identify high-risk patients and can lead to risk-reduction interventions. Implementation of the guidelines leads to elimination of unnecessary testing and intervention and reduction in cost of care. In short, preoperative stress testing performed according to the ACC/AHA guidelines is a valuable adjunct in triage of high-risk cardiac patients prior to major noncardiac surgery.

References

  1. ACC/AHA Task Force Report: Special Report: Guidelines for perioperative cardiovascular evaluation for noncardiac surgery. Circulation 1996; 93:1278-1317
  2. 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 ACC/AHA task force on practice guidelines (Committee to Update the 1996 Guidelines on Perioperative Cardiovascular Evaluation for Noncardiac Surgery) J Am Coll Cardiol 2002; 39:542-553
  3. Reilly D, McNeely MJ, Doerner D, et al. Self-reported exercise tolerance and the risk of serious perioperative complications. Arch Intern Med 1999; 159:2185-92
  4. Older P, Smith R, Courtney P, Hone R. Preoperative evaluation of cardiac failure and ischemia in elderly patients by cardiopulmonary exercise testing. Chest 1993; 104:701-4
  5. Shaw LJ, Eagle KA, Gersh BJ, Miller DD. Meta-analysis of intravenous dipyridamole-thallium-201 imaging (1985 to 1994) and dobutamine echocardiography (1991 to 1994) for risk stratification before vascular surgery. J Am Coll Cardiol 1996; 27:787-798
  6. Eagle KA, Rihal CS, Mickel MC, et al. Cardiac risk of noncardiac surgery: influence of coronary disease and type of surgery in 3368 operations. Circulation 1997; 96:1882-7
  7. Hassan SA, Hlatky MA, Boothroyd DB, et al. Outcomes of noncardiac surgery after coronary bypass surgery or coronary angioplasty in the bypass angioplasty revascularization investigation (BARI). Am J Med 2001; 110:260-6
  8. Poldermans D, et al for the Dutch Echocardiographic Cardiac Risk Evaluation Applying Stress Echocardiography Study Group. The effect of bisopropol on perioperative mortality and myocardial infarction in high risk-patients undergoing vascular surgery. N Engl J Med 1999; 341:789-94
  9. Boersma E, Poldermans D, Bax JJ, et al. Predictors of cardiac events after major vascular surgery: role of clinical characteristics, dobutamine echocardiography, and b-blocker therapy. J Am Med Assoc 2001; 285:1865-73
  10. Froehlich JB, Karavite D, Russman PL, et al. ACC/AHA Preoperative assessment guidelines reduce resource utilization prior to aortic surgery. J Vasc Surg 2002; 36:758-763

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