COMPARISON OF SYMPTOM-LIMITED AND LOW-LEVEL EXERCISE TOLERANCE-TESTS EARLY AFTER MYOCARDIAL-INFARCTION

Objectives. This study was conducted to determine the diagnostic yield and risks of a symptom-limited treadmill exercise test before hospital discharge. Background. Currently, predischarge low level and 6-week symptom limited exercise treadmill tests are recommended for risk stratification after myocardial infarction. However, few data exist on the safety and value of a predischarge symptom-limited exercise test. Methods. We utilized a modified Bruce protocol starting at 1.7 mph and 0 grade with 3-min stages in 150 consecutive patients 6.4 +/- 3.1 days after myocardial infarction. Each exercise test was interpreted for duration, symptoms and ST segment changes at the low level (70% of predicted heart rate) and symptom-limited end paint. Results. There were no complications related to the symptom-limited exercise tests. The test results were positive in only 23% of the patients at the low level end point, but were positive in 40% of the patients at the later symptom limited end point (p<0.001). During a mean follow up period of 15 +/- 5 months in 138 patients (92%), 50 patients (36%) had a cardiac event. Of the patients with a cardiac event, significantly more (p<0.001) had a positive exercise test at the symptom-limited end point (31 vs. 16 patients). Five patients with a negative and 14 patients with a nondiagnostic symptom-limited exercise test had an event. Conclusions. In patients with uncomplicated myocardial infarction, we demonstrated the safety of an early symptom-limited treadmill exercise test. Symptom-limited exercise tests will identify thy more patients with inducible ischemia who are at risk of future cardiac events and who may benefit from early intervention.