Cardiac rehabilitation (CR) offers a highly effective causative treatment of atherosclerotic coronary and peripheral disease. The life style and risk factor modifications achieved by CR have been shown to halt disease progression, and to reduce cardiovascular mortality and the rate of non-fatal myocardial infarction in patients with coronary artery disease. CR programs consist of exercise training, medical counseling, cardiovascular disease education, and psychosocial support. This comprehensive approach has significant benefits on exercise capacity, coronary risk factors, and health-related quality of life. In addition, CR reduces all-cause mortality as well as cardiovascular events. In general, CR programs consist of 3 stages : acute stage (phase I), convalescent stage (phase II), and chronic stage (phase III). In addition to this preventive approach, exercise-based intervention programs are also effectively used for chronic heart failure (CHF). Since exercise intolerance in CHF is primarily related to the degree of peripheral changes (such as muscle atrophy, reduced peripheral perfusion due to endothelial dysfunction, abnormalities in ventilation), regular aerobic training in CHF has been shown to improve peak oxygen uptake, to reduce peripheral vascular resistance, to retard or reverse muscle wasting, and to reduce morbidity. Despite its documented clinical effectiveness, rehabilitation and a preventive approach are still widely underutilized in Japan. However, it becomes increasingly clear that the use of interventional and surgical procedures is suboptimal therapy in the absence of simultaneous lifestyle modifications, including regular physical exercise and controlling cardiovascular risk factors.

The time constants of beat-by-beat heart rate decay for the first 30 seconds (T30) after exercise is a specific index for the vagally mediated component of heart rate recovery. The aim of our study was to determine whether cardiac rehabilitation (CR) can accelerate T30 in patients after coronary artery bypass grafting (CABG) . Thirteen male patients who underwent CABG (aged 60.5±7.7years) were assigned to 7-21 day Phase I CR. Exercise training consisted of 30 minutes of aerobic exercise (bicycle ergometer) at the anaerobic threshold 2 times per day. T30 was measured as the heart rate decay regulated in patients who rested immediately after 5 minutes of pedaling exercise. After CR, T30 significantly improved from 413.3±129.7 to 300.1±124.5 sec (p<0.01) . Peak oxygen uptake (peak V02: 14.0±4.0 16.7±3.2mlin/kg: p<0.01) and heart rate at anaerobic threshold (HR @ AT: 111.9±13.4 103.6±11.7 beatsin: p<0.01) also improved significantly. There was no correlation between ΔT30 (Δ: difference before and after CR) and Δpeak VO₂or ΔHR @ AT. These results suggest that CR for patients following CABG accelerates vagally mediated heart rate recovery after dynamic exercise.