Cardio-autonomic functions and sleep indices before and after coronary artery bypass surgery

BACKGROUND: Earlier studies showed a short-term impairment of cardio-autonomic functions following coronary artery bypass grafting (CABG). There is a lack of consistency in the time of recovery from this impairment. Studies have attributed the post-CABG atrial fibrillation to preexisting obstructive sleep apnea (OSA) without an objective sleep assessment. The aim of this study was to evaluate the effect of CABG on cardio-autonomic and hemodynamic functions and on OSA indices in patients with ischemic heart disease (IHD). METHODS: Cardio-autonomic function using heart rate variability indices, hemodynamic parameters, and sleep studies were performed in 26 patients with stable IHD before, on day-6, and day-30 post-CABG surgery. RESULTS: The high-frequency powers of normalized R-R intervals significantly (P = 0.002) increased from the preoperative value of 46.09 to 66.52 on day-6 and remained unchanged on day-30 postsurgery. In contrary, the low-frequency powers of normalized R-R interval decreased from 53.91 to 33.48 during the same period (P = 0.002) and remained unchanged on day 30 postsurgery. Baroreceptor sensitivity, obstructive and central apnea indices, desaturation index, and lowest O₂ saturation were not significantly different between preoperative, day-6, and day-30 postsurgery. CONCLUSION: Our study revealed that recovery of autonomic functions following CABG occurs as early as 30 days of postsurgery. CABG does not seem to have short-term effects on sleep study indices. However, long-term effects need further evaluation.