COMPARISON OF MAXIMUM VERSUS SUBMAXIMUM EXERCISE TESTING IN PROVIDINGPROGNOSTIC INFORMATION AFTER ACUTE MYOCARDIAL-INFARCTION AND OR CORONARY-ARTERY BYPASS-GRAFTING/

Exercise testing after acute myocardial infarction (AMI) provides prog nostic information. In many studies submaximum exercise tests performe d until a given work load, metabolic equivalents (METs) revel, or hear t rate were used or patients discontinued the exercise test prematurel y because of symptoms. We showed recently that peak oxygen uptake duri ng maximum exercise provides independent prognostic information in pat ients with coronary artery disease. It is, however, not known whether maximum exercise testing is superior in predicting mortality than test ing until a target level. Second, it is unclear which target end point best classifies patients at increased risk. Therefore, the independen t relation between mortality and indexes of, respectively, maximum and submaximum exercise capacity, were analyzed in 527 patients, who were tested until exhaustion. To express submaximum exercise capacity dich otomous variables (the ability to reach a target METs lever or not), a nd a continuous variable relative to maximum exercise capacity (the ve ntilatory anaerobic threshold) were used. After adjustment for signifi cant covariates, peak oxygen uptake was significantly related to all-c ause and cardiovascular mortality. The target level of 5 METs and the ventilatory anaerobic threshold, when expressed in absolute workload, were related to mortality when unadjusted, but after adjustment forage and other confounders significancy was lost. In multiple Cox regressi on analysis, the prognostic power of peak oxygen uptake remained signi ficant when 5 METs or the anaerobic threshold were forced into the equ ations. When analyzing the relation of various METs levels with mortal ity, the 7 METs level was independently related to all-cause and cardi ovascular mortality and yielded the highest diagnostic accuracy. We co nclude that maximum exercise testing is more potent in predicting mort ality than the ability to reach a predetermined level of exercise, suc h as the commonly used 5 METs level or the anaerobic threshold. Otherw ise, the use of a higher target level of 7 METs is recommended. (C) 19 97 by Excerpta Medica, Inc.