Preservation of myocardial function and metabolism at subzero nonfreezing temperature storage of the heart.

Background: The hypothermic simple immersion technique has been widely used to preserve the donor heart for transplantation. However, there is still controversy as to which temperature provides the best protection against prolonged ischemia. The low molecular weight solutes within cells depress the freezing point to -0.6 degree C. In practice, however, most cells do not freeze internally unless they are cooled below -10 degrees C. We investigated the effects of subzero nonfreezing storage at -1 degree C on the preservation of myocardial metabolism and function.

Methods: Isolated Wistar rat hearts were subjected to 6 hours of preservation with the intracellular type University of Wisconsin solution; the hearts of the subzero group were preserved at subzero nonfreezing (-1 degree C) temperature, and the hearts of the control group were at 4 degrees C. Recovery of cardiac function, myocardial adenine nucleotides content, and myocardial water content were evaluated after preservation.

Results: Subzero group resulted in significantly better aortic flow, cardiac output, and aortic systolic pressure than in the control group. Myocardial adenosine triphosphate, adenosine diphosphate, and total adenine nucleotides at end-storage were significantly better preserved in subzero group when compared with the control group. Myocardial water content at reperfusion significantly increased in the control group compared with the subzero group.

Conclusions: Storage in the intracellular type solution at subzero nonfreezing (-1 degree C) temperature as compared with 4 degrees C appears to prolong myocardial preservation with respect to the enhancement of postischemic functional recovery, preservation of myocardial adenine nucleotides during ischemia, and prevention of myocardial edema at reperfusion.