Cardiac rehabilitation after coronary artery bypass graft surgery: its effect on ischaemia, functional capacity, and a multivariate index of prognosis

Abstract

Objective: To assess the effect of cardiac rehabilitation on indices of ischaemia, functional capacity, and exercise test derived indices of prognosis in patients who undergo coronary artery bypass grafting (CABG).Patients and Methods : Prospective study of 150 consecutive cardiac rehabilitation patients who underwent coronary artery bypass grafting (CABG). Patients entered a hospital-based multidimensional cardiac rehabilitation programme with at least 2 months of regular supervised aerobic exercise as a main component. All patients underwent Bruce protocol exercise stress testing as a diagnostic procedure prior to surgery (ETT₁) and after surgery but prior to cardiac rehabilitation (ETT₂). A further exercise test was performed after 2 months of cardiac rehabilitation (ETT₃). Standard measurements during exercise ECG were obtained, including a Duke multivariate risk score. No restrictions were made on medical therapy. A total of 33 patients did not undergo a presurgery test, either because of unstable angina pectoris, or because of aortic stenosis. 2 patients did not complete the post rehabilitation exercise test. The data from 115 patients are presented. Results: Improvements in effort tolerance were seen at ETT₂ and ETT₃. (ETT₁ 3.8±0.4 min; ETT₂ 5.3±0.5 min; ETT₃ 6.4±0.5 min; all 2p<0.0001). Substantial improvements were seen after surgery in indices of ischaemia (ST segment shift and chest pain) and these were not further affected by cardiac rehabilitation (mean ST depression pre surgery 1.2±0.2 mm; ST depression post surgery and rehabilitation both 0.2±0.1 mm; 2p<0.0001 for change from ETT₁ only). Cardiac rehabilitation further enhanced effort tolerance, and increased maximal attainable systolic blood pressure (SBP). Maximal heart rate was unaffected (Maximal SBP: ETT₁ 161±5 mm Hg, ETT₂ 174±5 mm Hg, ETT₃ 182±5 mm Hg; 2p<0.0001 for ETT₂ vs ETT₁; 2p=0.003 for ETT₃ vs ETT₂). The Duke multivariate score improved after surgery, but a further improvement was seen after cardiac rehabilitation (Duke Score ETT₁ −5.4±1.3; ETT₂ +3.8±0.7; ETT₃ +4.7±0.8; 2p ETT₂ vs ETT₁ <0.0001; 2p ETT₃ vs ETT₂ >0.002).Conclusion : Dramatic benefits occur after cardiac surgery for symptoms of ischaemic heart disease. Cardiac rehabilitation does not have a further impact on either symptoms (lack of chest pain) or indices of ischaemia (ST segment depression). Cardiac rehabilitation does however further improve effort tolerance, increase maximal double product, and improve Duke prognostic score.