EXERCISE TESTING AND LEFT MAIN CORONARY ARTERY DISEASE: EXPERIENCE WITH 57 PATIENTS.

Results of multistage treadmill tests (TMT) of 57 patients with critical stenosis (>/= 50%) of the left main coronary artery were analyzed. Additional disease was present in the major vessel in three patients (5%), two vessels in 18 patients (32%), and three vessels in 35 patients (61%). The TMT was negative for ischemia in only two patients (4%), positive in 51 (89%), and undetermined in 4 (7%). TMT was strongly positive (>/= 2 mm ST segment depression) in 40 patients (70%), and in 11 (19%) of these, ST depression was >/= 3 mm. Hypotension with exercise was rare and was encountered in only one patient. Arrhythmias were induced with exercise in six patients (10%) and resulted in premature termination of TMT in four. TMT was terminated due to early ST segment depression in 40 patients (70%), in 17 (30%) without chest pain-an unusual finding. Exercise was limited to stage I (Bruce protocol) in 16 (28%), stage II in 26 (46%), stage III in ten (17%), and stage IV in five (9%). Mean exercise tolerance was 298 +/- 22 seconds (SEM). Maximum heart rate (HR) achieved was 76 +/- 2% of their maximal predicted values. Peak double product (systolic BP x HR) was 20490 +/- 830. The data suggest that the TMT is rarely negative in the presence of LM lesions. An early strongly positive response with or without pain should lead one to suspect LM disease. Exercise-induced hypotension is rare. Limited exercise tolerance and/or early ST segment depression in stages I and II of TMT seem to be predictive of the severity of LM lesions.