Correspondence

Assessment of Cardiac Risk before Abdominal Aortic Surgery

N Engl J Med 1994; 331:480August 18, 1994

Article

To the Editor:

The recent article by Baron and colleagues (March 10 issue)1 provides further evidence that Bayesian principles are essential as physicians consider the appropriate prognostic stratification of candidates for major vascular surgery. When the Journal published the first report of the value of dipyridamole-thallium imaging before such procedures, all patients in the study had a history of myocardial infarction or established angina pectoris2. The high positive predictive value of the test was dependent on the high prior probability of underlying coronary disease (90 to 100 percent).

Over the past nine years, a number of investigators have used both exercise and non-exercise stress testing for preoperative risk assessment. Because of differences in patient selection in these studies, including that by Baron et al., the overall prior probability of underlying coronary heart disease was much lower than in the original cohort studied by Boucher et al.2 Furthermore, with falling rates of perioperative complications as a result of the increasingly aggressive use of hemodynamic monitoring and antiischemic medications, as well as improvements in anesthesia and postoperative pain control, the predictive accuracy of testing for the purpose of determining the risk of short-term perioperative events is diminished further.

In this context, we have argued that physicians should use a Bayesian approach to select the subgroup of patients who might benefit from preoperative testing beyond simple clinical assessment3,4. Baron and colleagues corroborate previous findings that clinical factors are extremely important in identifying patients who are at particularly high risk. Variables that are especially predictive include evidence of established coronary heart disease (manifested by myocardial infarction, angina pectoris, or pathologic Q waves on the electrocardiogram) and advanced age. Additional correlates include diabetes and markers of left ventricular dysfunction such as congestive heart failure or ventricular arrhythmias. Although the positive predictive value of such clinical markers is limited, the absence of such variables (aggregate predictive value, negative) suggests a very low risk of perioperative cardiac events.

For patients who are thought to be at moderate-to-high risk, exercise and non-exercise stress testing may help identify patients who may be at markedly elevated risk not only for poor outcomes in the short term but also, especially, for cardiovascular events over the long term. The goal is to use stress testing in a discriminating manner to identify patients with left main or multivessel coronary disease for whom coronary revascularization, with either coronary angioplasty or bypass grafting, may reduce perioperative and long-term risk.

Kim A. Eagle, M.D.
Richard Cambria, M.D.
Christopher Coley, M.D.
William Abbott, M.D.
Massachusetts General Hospital, Boston, MA 02114

4 References

1. 1

   Baron J-F, Mundler O, Bertrand M, et al. Dipyridamole-thallium scintigraphy and gated radionuclide angiography to assess cardiac risk before abdominal aortic surgery. N Engl J Med 1994;330:663-669
   Full Text | Web of Science | Medline

2. 2

   Boucher CA, Brewster DC, Darling RC, Okada RD, Strauss HW, Pohost GM. Determination of cardiac risk by dipyridamole-thallium imaging before peripheral vascular surgery. N Engl J Med 1985;312:389-394
   Full Text | Web of Science | Medline

3. 3

   Eagle KA, Singer DE, Brewster DC, Darling RC, Mulley AG, Boucher CA. Dipyridamole-thallium scanning in patients undergoing vascular surgery: optimizing preoperative evaluation of cardiac risk. JAMA 1987;257:2185-2189
   CrossRef | Web of Science | Medline

4. 4

   Eagle KA, Coley CM, Newell JB, et al. Combining clinical and thallium data optimizes preoperative assessment of cardiac risk before major vascular surgery. Ann Intern Med 1989;110:859-866
   Web of Science | Medline

Author/Editor Response

Dr. Baron replies:

To the Editor: The principal finding of our study was that definite clinical evidence of coronary artery disease and older age are the two most important variables correlated with adverse cardiac outcomes in patients undergoing abdominal aortic surgery. These findings corroborate previous findings. Eagle and coworkers identified clinical predictors of adverse cardiac outcomes very similar to those we reported.1

On the basis of our findings, the rate of perioperative complications could be quantified as follows: in patients 65 years of age or younger who did not have definite coronary artery disease (37 percent), the rate of cardiac complications was only 10 percent; in patients with one of the two predictors (63 percent), the rate of cardiac complications was 24 percent; and in patients with both predictors (17 percent), it was 39 percent.

We propose the following guidelines for the preoperative assessment of cardiac risk:

First, it seems clear that in patients with low risk (those who have neither of the predictors), there is probably no reason to perform additional tests.

Second, in patients with a high risk of cardiac complications (those with both predictors), who make up a small group (<20 percent), it seems cost effective to perform coronary angiography and, when indicated, percutaneous transluminal coronary angioplasty or coronary-artery bypass grafting.

Third, the chief problem is presented by patients at moderate risk (those with one of the two predictors), because they are the largest group (63 percent) and because the prevalence of coronary artery disease in this group is probably lower than that in patients with both predictors. In this subgroup, the positive and negative predictive value of exercise and non-exercise stress tests will be very much lower than in patients with a high prevalence of coronary artery disease. Therefore, we were not able to confirm the results of Eagle et al.,1 which suggest that in this subgroup dipyridamole-thallium scintigraphy could optimize stratification according to risk.

Jean-Francois Baron, M.D.
75014 Paris, France, Hopital Broussais

1 References

1. 1

   Eagle KA, Singer DE, Brewster DC, Darling RC, Mulley AG, Boucher CA. Dipyridamole-thallium scanning in patients undergoing vascular surgery: optimizing preoperative evaluation of cardiac risk. JAMA 1987;257:2185-2189
   CrossRef | Web of Science | Medline

Citing Articles (1)

Citing Articles

1. 1

   Sylvia Archan, Christopher R. Roscher, Ronald M. Fairman, Lee A. Fleisher. (2010) Revised Cardiac Risk Index (Lee) and Perioperative Cardiac Events as Predictors of Long-term Mortality in Patients Undergoing Endovascular Abdominal Aortic Aneurysm Repair. Journal of Cardiothoracic and Vascular Anesthesia 24:1, 84-90
   CrossRef