Serial changes of heart rate variability after coronary artery bypass surgery

Aim of the present study was to assess autonomic modulation of heart rate by heart rate variability (HRV) analysis in frequency domain after coronary artery bypass graft surgery (CABG) in patients with coronary artery disease, its relations with clinical variables and dynamics during follow-up period. Twenty patients (mean age 46.8 ± 8.8 years) with coronary artery disease, submitted to CABG, entered the study. All the patients were examined clinically and electrocardiogram, chest X-Ray and two-dimensional echocardiogram were performed. Heart rate variability was assessed by means of frequency-domain analysis (Fourier transform). Investigations were undertaken before, 7 days, 30 days and 3 months after surgery. A significant overall reduction occurred in HRV component's powers after CABG (p < 0.0001), followed by a gradual increase with restoration of preintervention levels in the 3rd month after surgery. The attenuation of HRV indices was dependent on duration of aortic cross clamping time (r = -0.62, p < 0.003) and cardiopulmonary bypass time (r = -0.60, p < 0.004). In conclusion, heart rate variability decreases after coronary artery bypass surgery, with further restoration in the 3(rd) month after surgery. The deterioration of HRV indices is dependent on the duration of cardiopulmonary bypass time and aortic cross-clamping time