IMPROVED RAT-HEART FUNCTION AFTER LOW CA2+ PERFUSED PRESERVATION AT 5-DEGREES-C FOR 18 HOURS

To evaluate the effect of Ca2+ on recovery of heart function after hypothermic preservation, isolated working rat hearts were perfused continuously in different [Ca2+] (0.35-2.0 mM) at 37 degrees C for 30 min, during cooling to 5 degrees C, and then at 5 degrees C for 1, 6 or 18 h. After rewarming to 37 degrees C, contractile functions were assessed in working hearts perfused with Krebs-Henseleit (K-H) solution containing 2.0 mM free Ca2+. Ln normal R-H solution (2.0 mM Ca2+), cardiac function recovered completely after perfusion at 5 degrees C for 1 h (measured by the maximal rate of pressure development, + dP/dt(max), and heart rate x left ventricular systolic pressure, HR x LVSP). After 6 h at 5 degrees C, significant (P < 0.05) loss in function began to appear. Further, 18 h at 5 degrees C resulted in significant decreases in LVSP, + dP/dt(max), and coronary now (CF) and a significant increase in left ventricular diastolic pressure. The deterioration of heart function consequent to hypothermic preservation could be prevented by reducing the Ca2+ in perfusion medium prior to and during cooling and rewarming from hypothermia. The optimal Ca2+ concentration was 0.5 mM. At lower Ca2+ (0.35 mM), reductions in HR, LVSP, +dP/dt(max), and CF after rewarming were evident. Our results indicate that by reducing cellular Ca2+ prior to cooling through perfusion of 0.5 mM Ca2+ K-H solution, significant benefits can be obtained both in prolonging the duration of cardiac preservation and in retaining functional integrity upon rewarming. (C) 1994 Academic Press, Inc.