Improvement in exercise tolerance in patients with impaired left ventricular function following coronary revascularization

We retrospectively investigated the effects of coronary artery bypass grafting on exercise tolerance in 17 patients with triple vessel disease and diminished ejection fraction (21 to 40%; 31.8 ± 7.3). The patients (42-63 years; 54.8 ± 5.7), were stratified into an impaired ejection fraction group, (30 to 40%; 36.6 ± 3.4; n = 11); and a severely impaired group, (20 to 29%; 23 ± 2.1; n = 6). Patients were subjected to a maximal exercise tolerance test using a Bruce protocol, prior to and 3.8 ± 1 months after surgery. Repeated measures Analysis of Variance revealed a significant (p < 0.05) enhancement in variables with no between-group interaction suggesting a similar post-surgery test response. Significant improvement in exercise tolerance for the study population was demonstrated by a: 36% increase in exercise intensity, (5.5 ± 2.5 to 7.5 ± 2.9 METS); 47% increase in exercise duration, (5.9 ± 2.2 to 8.7 ± 2.4 min); 12% increase in peak heart rate, (121 ± 21 to 136 ± 24 beats x min -1 ); and 18% increase in peak rate pressure product, (182.8 ± 55 to 217.3 ± 65). In addition, subjective measures for test termination changed from dyspnea and chest pain to muscle fatigue in a majority of subjects. Exercise tolerance was equally enhanced in both the impaired and severely impaired groups following bypass surgery. Further investigation examining the effects of surgical intervention in these patient populations as well as the mechanisms responsible for the improvement is warranted.