Delayed recovery of cardiovascular autonomic function after mitral valve surgery: Evidence for direct trauma?

Baroreflex Sensivity (BRS) and heart rate variability (HRV) have significant influence on the patients' prognosis after cardiovascular events. The following study was performed to assess the differences in the postoperative recovery of the autonomic regulation after mitral valve (MV) surgery and aortic valve (AV) surgery with heart-lung machine. 43 consecutive male patients were enrolled in a prospective study; 26 underwent isolated aortic valve surgery and 17 isolated mitral valve surgery. Blood pressure, ECG and respiratory rate were recorded the day before, 24h after surgery and one week after surgery. BRS was calculated according to the Dual Sequence Method, time and frequency parameters of HRV were calculated using standard methods. There were no major differences between the two groups in the preoperative values. At 24 h a comparable depression of HRV and BRS in both groups was observed, while at 7 days there was partial recovery in AV-patients, which was absent in MV-patients: p (AV vs. MV)<0,001. While the response of the autonomie system to surgery is similar in AV- and MV-patients, there obviously is a decreased ability to recover in MV-patients, probably attributing to traumatic lesions of the autonomic nervous system by opening the atria. Ongoing research is required for further clarification of the pathophysiology of this phenomenon and to establish strategies to restore autonomic function.