Aortic valve replacement: better myocardial protection by cold or warm retrograde blood cardioplegia?

To determine whether warm blood cardioplegia (BCP) is superior to cold BCP in terms of myocardial protection, we compared warm (37 degrees C) and cold (4 degrees C) continuous retrograde administration of BCP in 40 patients undergoing aortic valve replacement (AVR) in a prospective, randomized study.

The main subjects of investigation were the myocardial oxygen consumption and the maintenance of the ultrastructure of the tissue. In addition, we looked at intraoperative recordings of time, heart rhythm disturbances, CK/MB serum levels, and inotropic support.

We found, that oxygen consumption is significantly higher during warm BCP (7.95-10.38 ml/min) than during cold BCP (2.11-3.47 ml/min). Mild, reversible myocardial damage occurs during cold and warm BCP. The intraoperative serum potassium level was significantly higher after warm (7.25 mmol/l) than after cold (6.55 mmol/l) BCP. There was no statistically significant difference in the duration of extracorporeal circulation and of cardiac arrest, the CK/MB serum level or the recorded right and left ventricular performance data in the two groups.

We conclude that continuous retrograde warm BCP is not superior to continuous retrograde cold BCP as far as myocardial protection is concerned. The administration of cold BCP prolongs the tolerated ischemic time of the myocardium and provides a higher safety margin.