Myocardial protective effect of deep hypothermic cardiac arrest without aortic cross clamp in neonatal hearts: comparison with cardioplegic arrest in a rabbit model.

Using an isolated perfusion model of neonatal rabbit hearts aged 3 to 6 days, cardioplegic arrest (CPA) using crystalloid cold cardioplegia with aortic cross clamp (AXC: 60 min, n = 15) and continuous deep hypothermic perfusion (DHP) at 15 degrees C without AXC (n = 15) were compared. The hearts were divided into two subgroups: intact hearts (n = 18) and with preceding 40 min warm ischemia (stressed hearts, n = 22). In the intact hearts, there were no significant differences between the CPA and DHP groups in left ventricular function, myocardial water content, and myocardial mitochondrial score after reperfusion. In the stressed hearts, recovery of cardiac output and left ventricular work was significantly higher in the DHP group than in the CPA group. The post-reperfusion myocardial mitochondrial score was significantly better in the DHP group than in the CPA group. These results suggest that non-AXC DHP may be advantageous in the setting of stressed hearts with preceding ischemic injury where conventional CPA cannot provide adequate myocardial protection.