Exercise testing after myocardial infarction: a perspective.

Background. In subjects without known coronary artery disease, an abnormal exercise test is an adverse prognostic indicator with respect to future coronary events (1,2). In patients with angiographically documented coronary disease, poor exercise tolerance and exercise-induced ST depression are associated with a poor prognosis (3,4). Exercise testing provides additional prognostic data even when the extent of coronary disease and left ventricular dysfunction are known (3,4). Ten years ago in North America, exercise testing was considered to be contraindicated within 2 to 3 months after myocardial infarction (5). Studies since then have concluded that an exercise test done soon after myocardial infarction can reveal abnormalities associated with an increased subsequent risk: ST depression (6-8), poor exercise tolerance (9-11), an inappropriate blood pressure response (12,13), ventricular arrhythmias during exercise (10,12), exerciseinduced myocardial hypoperfusion (14) and exercise-induced left ventricular dysfunction (15). Controversy exists as to which of these predictors are best and to what extent they add prognostic information to clinical data already available (16). The MILlS database. The study by Stone et al. (17) in this issue of the Journal provides new and interesting information relevant to this controversy. Two-thirds (473) of 719 survivors at 6 months after infarction underwent maximal exercise testing. Their mortality over the next 12 months was 3%, compared with 16% in patients not tested because of cardiac limitations. Clinical findings (angina and heart failure) predicted mortality only among patients who were not tested. Exercise-induced ST elevation, an inadequate blood pressure response, exercise-induced ventricular premature beats and poor exercise tolerance all presaged an increased mortality. How should these results influence our management of patients after myocardial infarction? Spe-