Prediction of functional capacity and use of exercise testing for predicting risk after acute myocardial infarction

This study evaluated whether an ischemic exercise test response or functional capacity could be predicted from data available during hospitalization in patients discharged after acute myocardial infarction (AMI). The value of exercise test variables for predicting death and new AMI within 1 year was also examined. Among 1,469 patients, 466 (32%) underwent treadmill exercise testing around the time of discharge. An ischemic exercise test response (ST-segment depression or angina) could not be predicted. Good functional capacity (more than 4 METs) could be predicted from age and ST-segment changes at rest. Among the 60% of the patients who were predicted to have functional capacity of more than 4 METs, only 15% had poor functional capacity at the time of testing. Multivariate analysis for predicting death and new infarction selected only functional capacity (continuous variable in METs), which classified 72% of the patients into a low-risk group with less than a 2% rate of death and new AMI in the first year. The high-risk group (29% of the patients) had an 18% rate of death or new AMI. It is concluded that functional capacity is the most important exercise test variable and that patients likely to have good functional capacity can be identified on the basis of age and ST-segment changes at rest. Further, the level of functional capacity on exercise testing can identify groups of patients with very low and relatively high risk of death or new AMI within 1 year.