Electrocardiographic abnormalities during exercise 3 weeks to 18 months after anterior myocardial infarction.

The electrocardiographic abnormalities produced by exercise at varying time intervals after an anterior myocardial infarction were studied in 12 patients. Three weeks after the infarction, exercise induced an obvious rise in the ST segment in leads over the infarcted area in IO patients. In the course of the ensuing months this reaction to exercise gradually disappeared, and in some subjects exercise then produced ST segment depression. The ST rise produced by exercise in the early phase after an infarction is interpreted as a sign of anoxia in the infarcted zone, and the rate at which this pattern resolves may be ofprognostic value. These changes in the ST-T wave produced by exercise were not found in left praecordial leads distant from the site of infarction. The T wave amplitude was found to be increased during exercise at all times after infarction, but this change is nonspecific.