Heart rate variability after coronary artery bypass graft surgery:: A prospective 3-year follow-up study

Background: Autonomic heart rate control is impaired after CABG. The aim of this study was to establish the temporal pattern of change in the decrease of HRV observed after CABG. Methods and Results: Twelve patients with coronary artery disease were assessed with 24-hour Holter recordings 2 days before CABG and 1 week, 3 months, 6 months, 1 year, and 3 years after CABG. All the time-domain and frequency-domain HRV parameters decreased precipitately after CABG and were mostly recovered 3 months after CABG except mean NN, rMSSD, and pNN50. The ratio of LF to HF showed a slight decrease after surgery, recovered to preoperative values after 3 months, surpassed, and continued to increase 6 months after surgery. At 3 years of follow-up the recovery was complete. The rate of change of time-domain and frequency-domain parameters were calculated and their correlation with aortic cross-clamping time, number of vessels bypassed, the amount of cardioplegic used were sought and no statistically significant correlation was found. Conclusion: The recovery of HRV regardless to the preoperative state of the patients and their postoperative course implies that the early drop of HRV after CABG was related to the acute effects of surgery. Late complete recovery of HRV may be due to resolution of ischemia or use of angiotensin-converting enzyme inhibitor.