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

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 < .0001). Of those who took the test, 12% subsequently underwent bypass graft surgery compared with 14% of those who did not (p > .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 < .001), ability to complete the 9 min test (3% vs 8%; p < .01), and the absence of couplets (4% vs 13%; p < .05) or any ventricular ectopic depolarizations (4% vs 7%, p < .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 < .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.