Effects of cardiac rehabilitation and exercise training on autonomic regulation in patients with coronary artery disease

BACKGROUND: Although cardiovascular rehabilitation and exercise training have substantial benefits in various ischemic heart disease (IHD) risk factors and subsequent prognosis after major IHD events, there is a paucity of information about its effects on autonomic regulation (such as heart rate variability [HRV] and baroreflex gain), particularly considering its arterial and cardiopulmonary components. METHODS: We studied 40 patients (aged 60 +/- 6 y) after major IHD events, including 29 who underwent a comprehensive phase II cardiac rehabilitation and exercise training program and 11 controls who did not attend cardiac rehabilitation. Specifically, we determined whether active training improves prognostic indices of autonomic regulation of the SA node and whether changes in baroreflex gain could be ascribed to the arterial or to the cardiopulmonary component of the overall arterial pressure/heart period baroreflex. RESULTS: Only patients with IHD undergoing active rehabilitation demonstrated a significant increase in R-R interval, in its variance, in overall gain of arterial pressure/heart period baroreflex (7.44 +/- 1.20 ms/mm Hg to 12.12 +/- 1.48 ms/mm Hg, P <.001) and in peak oxygen consumption (Delta = 2.45 mL/kg/min, P <.001). Separate examination of the selective arterial and cardiopulmonary components showed that only the latter increased significantly (6.17 +/- 1.09 ms/mm Hg to 10.62 +/- 1.56 ms/mm Hg; P <.01). CONCLUSIONS: Cardiac rehabilitation is associated with significant improvements in autonomic markers of neural regulation of the SA node, such as increases in R-R variance and the gain of the overall spontaneous baroreflex, with specific improvements in the cardiopulmonary component as opposed to the arterial baroreflex component of this system. These improvements may further explain the reduction in morbidity and mortality noted after formal cardiac rehabilitation and exercise training programs.