Left-ventricular function and autonomic cardiac adaptations after short-term inpatient cardiac rehabilitation: a prospective clinical trial.

OBJECTIVE Cardiac rehabilitation is associated with cardiac autonomic and physiological benefits. However, it is unclear whether baseline left ventricular function (LVF) impacts on training-induced cardiac autonomic adaptations. The aim of this study was to assess the cardiac autonomic adaptations in patients with varying left ventricular function profiles undergoing coronary artery bypass grafting and cardiac rehabilitation. DESIGN Assessor-blinded prospective trial. PATIENTS Forty-four patients undergoing coronary artery bypass grafting, divided into normal LVFN (≥ 55%, n = 23) or reduced LVFR (35-54%, n = 21) were evaluated. METHOD Cardiac autonomic function was evaluated by heart rate variability indexes obtained both pre- and post-cardiac rehabilitation. All patients participated in a short-term (approximately 5 days) supervised inpatient physiotherapy program. RESULTS There were differences in heart rate variability indexes, correlation dimension and SD2 according to time and group (e.g. interaction time (effect of cardiac rehabilitation) vs group (LVFN vs LVFR), p = 0.04). Simple main effects analysis showed that the LVFR group benefited to a greater degree from cardiac rehabilitation compared with the LVFN group. Heart rate variability indexes increased significantly in the former group compared with the latter. CONCLUSION Among post-coronary artery bypass grafting patients engaged in short-term inpatient rehabilitation, those with reduced left ventricular function are most likely to have better cardiac autonomic adaptations to exercise-based rehabilitation.