Figure 52-4 Algorithm for combining clinical variables and dipyridamole-thallium results to stratify cardiac risk in vascular surgery patients. Cardiac events include unstable angina, myocardial infarction, ischemic pulmonary edema, and cardiac death. Clinical variables are the Q wave on electrocardiogram, age older than 70 years, history of angina, ventricular ectopic activity requiring treatment, and diabetes mellitus requiring treatment. (From 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 110:859–866, 1989.)