Long-term preservation of the mammalian myocardium. Effect of storage medium and temperature on the vulnerability to tissue injury.

Abstract

Human heart preservation for transplantation commonly involves infusion of cold cardioplegic solutions and subsequent immersion in the same solution. The objectives of the present study were (1) to establish the temporal relationship between storage time (at 10 degrees C) and the postischemic recovery of function in the isolated rat heart, (2) to assess, by metabolic and functional measurements, whether storing the heart in fluid as opposed to moist air had any effect on the viability of the preparation, and (3) to ascertain the optimal storage temperature. Isolated rat hearts (at least 6 in each group) were infused for 3 minutes with St. Thomas' Hospital cardioplegic solution No. 2 at 10 degrees C, stored at 10 degrees C for 6, 12, 18, or 24 hours, and then reperfused at 37 degrees C. Mechanical function, assessed by construction of pressure-volume curves (balloon volumes: 20, 40, 60, 80, 100, and 120 microliters), was measured before ischemia and storage and after 60 minutes of reperfusion. Function deteriorated in a time-dependent manner; thus at a balloon volume of 60 microliters the recovery of left ventricular developed pressure was 84.2% +/- 5.3% after 6 hours (p = not significant when compared with preischemic control); 69.1 +/- 3.3% after 12 hours (p less than 0.05); 55.6% +/- 4.4% after 18 hours (p less than 0.05), and 53.0% +/- 6.8% (p less than 0.05) after 24 hours of storage. Other indices of cardiac function, together with creatine kinase leakage and high-energy phosphate content, supported these observations. Since the recovery of the left ventricular developed pressure balloon volume curves were essentially flat after 18 and 24 hours of storage, either 6 or 12 hours of storage were therefore used in subsequent studies. Comparison of storage environment (hearts either immersed in St. Thomas Hospital cardioplegic solution No. 2 or suspended in moist air at 10 degrees C for 6 or 12 hours) revealed no significant differences in functional recovery between the groups. Thus hearts recovered 94.9% +/- 3.5% and 113.7% +/- 12.4%, respectively, after 6 hours of storage and 71.6% +/- 2.4% and 54.2% +/- 7.9%, respectively, after 12 hours of storage. Enzyme leakage and tissue water gain were also similar in both groups of hearts. Finally, hearts (n = 6 per group) were subjected to 12 hours' storage at 1.0 degree, 5.0 degrees, 7.5 degrees, 10.0 degrees, 12.5 degrees, 15.0 degrees, and 20.0 degrees C.(ABSTRACT TRUNCATED AT 400 WORDS)