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 (Delta)VO2/Deltawork 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 < 0.01), but not in controls or in group 2. Also the DeltaVO2/Deltawork relationship, above the ischaemic threshold, flattened in group 1, but not in group 2.
Conclusion: The suggestion of major coronary disease in patients with exercise-induced ST changes is given by: (i) a flattening of the DeltaVO2/Deltawork relationship, above both the ischaemic and anaerobic thresholds; and (ii) low VO2 values at anaerobic and ischaemic thresholds.