Predictive implications of stress testing. Follow-up of 2700 subjects after maximum treadmill stress testing.

Follow-up data on 2700 subjects who had had maximum stress tests were assembled in life tables. A positive test, characterized by ST-segment depression of 1.5 mm, 0.08 sec from the J point, predicted an incidence of some new coronary event of 9.5% a year, as compared with 1.7% in those with a negative test. The incidence of infarction and death was also significantly higher than in the negative responders. Early onset of ischemia occurring at moderate exercise (4 metabolic equivalents-METS) resulted in an incidence of all coronary events of 15% a year, while ischemia first manifested at the seventh minute of exercise (approximately 8 METS) results in an incidence of only 4% per year. The magnitude of ST depression and the age of onset of ischemia failed to influence the incidence of coronary events. A myocardial infarction previous to the test increased the incidence of events in both positive and negative responders. The positives with a previous infarction had more than double the incidence of coronary events than the positive responders with no pre-existing infarction. Those with chronotropic incompetence had a high incidence of coronary events even though the ECG response to exercise was normal.