Session P74.4

Depression of Cardiovascular Autonomic Function after Open Heart Surgery: Effects of Surgical Trauma

B Retzlaff*, H Malberg, N Wessel, G Brockmann,
C Uhl, R Lange, R Bauernschmitt

German Heart Center
Munich, Germany

The well-known depression of cardiovascular autonomic function following cardiac surgery is related to a variety of reasons like anesthesia and the use of the heart-lung-machine. The role of direct surgical trauma to the autonomic nerves (AN) is still unclear. The following study was performed comparing patients with isolated aortic valve replacement (AV, the surgical trauma to AN is considered to be low) or isolated mitral valve surgery (MV, high surgical trauma to AN is expected). 62 consecutive patients undergoing single aortic or mitral valve surgery were analysed. Patients with concomitant coronary heart disease were excluded for the known effects of atherosclerosis. Perioperative medication was standardized. After 10-min equilibrations to the environment, non-invasive blood pressure signals were collected from the radial artery by a tonometer (Colin Medical Instruments) at 1000 Hz. Simultaneously, breathing excursions and a standard ECG were monitored. Data were sampled for a 30-min period the day before surgery, 24h and seven days after surgery. Care was taken to perform the measurements during the same time of the day in each patient. Heart rate variability (HRV) and Baroreflex Sensitivity (BRS) were calculated using standard methods. There were no major differences among the two groups preoperatively. At 24h after surgery, both groups showed a comparable depression of HRV and BRS. One week after surgery, however, marked differences were present: SDNN 14+/-6 (MV) vs. 38+/-34 (AV); p<0.001. HF 0.01+/-0.01 (MV) vs. 0.31+/- 0.59 (AV); p<0.02. BRS bradycardic 4.5+/-1.7 (MV) vs. 6.3+/-3.6 (AV); p<0.02. The similar depression in both groups observed at 24h may reflect the effects of standardized anesthesia and perioperative treatment being comparable in all patients. While AV-patients showed a clear tendency to recover after one week, no recovery was recorded in MV-patients. This is the first evidence of higher direct surgical trauma to AN, if the atria are dissected.

(Abstract Control Number: 191)