Experimental evaluation of hypothermic intermittent coronary perfusion

Abstract

The recovery of the myocardial contractility of blood-perfused papillary muscle from the rabbit hearts was used to determine if hypothermia would minimize the myocardial injury associated with intermittent aortic cross-clamping (IACC). Continuous normothermic coronary perfusion for 2 hours with either cross circulation or a membrane oxygenator had only minimal adverse effects on contractility. None of the hearts tolerated normothermic IACC (45 minutes of anoxia and 10 minutes of reperfusion, repeated twice), When the myocardial temperature was reduced to 32 degrees C., the recovery following IACC was 41.25 +/- 11.21 percent (n=8). With hypothermia of 28 degrees C., it was 70.43 +/- 13.03 percent (cross circulation group, n=7) or 68.36 +/- 13.11 percent (membrane oxygenator group, n=7). If the hearts were cooled to 24 degrees C., the recovery of the myocardial contractility following IACC was 90.95 +/- 5.42 percent (n=11). The improvement of the degree of recovery by hypothermia was statistically highly significant (p less than 0.005). Creatine phosphokinase (CPK) and isoenzymes (CPK-MB) were also measured in some groups, but the results warrrant further studies before they can be correlated with the myocardial function.