Alterations in spectral characteristics of heart rate variability as a correlate of cardiac autonomic dysfunction after esophagectomy or pulmonary resection

Background: Both esophagectomy and pulmonary resection are associated with postoperative cardiac complications, partly because of autonomic perturbations involving the heart, This study was undertaken to determine whether heart rate variability (HRV), employed as an index of cardiac autonomic function, changes in patients undergoing esophagectomy or pulmonary resection. Methods: Electrocardiographic RR intervals were measured in 20 esophagectomized patients, 10 undergoing right and 10 undergoing left pulmonary resection on the preoperative day as baseline data and on postoperative days 1, 3, 5, 7, 14, and 30. Instantaneous heart rate was calculated every 250 ms from 416-s data of RR intervals. Power spectra of HRV for 128 s were computed using a fast Fourier transform and normalized by squared mean heart rate. The averaged ten sets of normalized HRV power were obtained by integrating the following power spectral bands: the low-, (0.06-0.10 Hz), high- (0.15-0.40 Hz), and total-frequency regions (0.01-0.40 Hz). Results: In the esophagectomy group, mean low-, high-, and total-frequency HRV power decreased after surgery to 17%, 6%, and 15% of their preoperative values, respectively, and these indexes remained suppressed for up to 30 days. After right pulmonary resection, low- and total-frequency HRV power decreased through 30 and 7 postoperative days, respectively. In the left pulmonary resection group, HRV remained unchanged. in the esophagectomy group, mean (+/-SEM) heart rate increased from 78 (+/-3) bpm to more than 90 bpm throughout the study, and body temperature from 36.5 (+/-0.1)degrees C to more than 37.0 degrees C through 14 postoperative days. Heart rate and body temperature remained increased for 3 days after pulmonary surgery. Mean arterial pressure remained unchanged in the three surgical groups. Conclusions: Reductions in HRV after esophagectomy or right pulmonary resection indicate a substantial and prolonged surgical injury to the autonomic nervous control of pulse rate.