Cardiopulmonary evidence of exercise-induced silent ischaemia

BACKGROUND: Exercise-induced ST changes, suggestive of cardiac ischaemia, are found in asymptomatic patients. METHODS: Gas exchange kinetics were studied during exercise to help to separate patients affected by epicardial coronary disease from those without. Forty-eight patients, without angina symptoms and showing significant changes of ST during exercise, underwent a coronarography and maximal cardiopulmonary exercise test. Thirty-five healthy individuals of matched age and sex underwent a cardiopulmonary exercise test as controls. RESULTS: Patients were grouped according to the presence (group 1, n=35) or the absence (group 2, n=13) of significant coronary lesions at angiography. When corrected for predicted oxygen consumption (VO2) at peak exercise and at anaerobic threshold, results showed a low VO2 at peak exercise and anaerobic threshold in group 1 (68±19 and 84±17% of predicted, respectively) compared with normal subjects (91±19 and 96±24% of predicted VO2) and group 2 patients (86±17 and 96±18%). Also the ischaemic threshold, when normalized for predicted workload at peak exercise, occurred earlier in group 1 (67±22%) than in group 2 (87±19%). The time-related (Δ)VO2/Δwork relationship showed a significant flattening above the anaerobic threshold in group 1 (7.4±2.2 versus 9.4±1.4 ml/watt per minute, P