Low-level exercise testing after myocardial infarction: usefulness in enhancing clinical risk stratification.

Abstract

Of 866 patients enrolled in our multicenter study, 667 performed a low-level exercise test early after myocardial infarction, most before discharge. Excluding seven patients who died before the test could be considered, there was a 14% 1 year cardiac mortality in 192 patients who did not take the test (150 for medical and 42 for logistic reasons) compared with 5% in those who did (p less than .0001). Of those who took the test, 12% subsequently underwent bypass grafts surgery compared with 14% of those who did not (p greater than .05). Decreased mortality in the year after the infarction in those taking the test was associated with an increase in blood pressure to 110 mm Hg or higher (3% vs 18%; p less than .001), ability to complete the 9 min test (3% vs 8%; p less than .01), and the absence of couplets (4% vs 13%; p less than .05) or any ventricular ectopic depolarizations (4% vs 7%, p less than .05) before, during, or after exercise. Achievement of a blood pressure of 110 mm Hg or higher during exercise in patients with no evidence of pulmonary congestion on the chest x-ray identified a group of 454 patients (70% of those taking the test) with a 1 year cardiac mortality of 1% compared with 13% in the remaining patients (p less than .0001). Logistic models showed that the exercise test contributed independent prognostic information for cardiac death, new infarction, and bypass surgery. Results of low-level exercise testing before hospital discharge combined with clinical features of the infarction can effectively identify patients at low risk for subsequent cardiac mortality.