Comparison of symptom-limited and low level exercise tolerance tests early after myocardial infarction

Objectives. This study was conducted to determine the diagostic 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 stage in 150 consecutive patients 6.4 ± 3.1 days after myocardial infraction. Each exercise test was interpreted for duration, symptom and ST segment changes at the low level (70% of predicted heart rate) and symptom-limited end point.Results. There were no complications related to the symptom-limited exercise test. 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.Conclusion. In patients with uncomplicated myocardial infarction, we demonstrated the safety of an early symptom-limited treadmill exercise test. Symptom-limited exercise tests will identify more patients with inducible ischemia who are at risk of future cardiac events and who may benefit from early intervention.