Twenty-Four-Hour Intermittent Perfusion Storage of the Isolated Rat Heart: II. Perfusion Pressure and Functional Preservation

Abstract

This study investigated the effect of intermittent perfusion (IP) pressures on functional preservation of the cold-stored isolated rat heart. The heart was flushed with cardioplegic solution #11 with ethylene diaminetetraacetic acid and 2, 3-butanedione monoxime (CP-11EB), and stored at 0°C for 24 hr. During storage, the heart was intermittently perfused for 3 min at 10 and 17 hr of storage with 25°C oxygenated CP-11EB. The IP pressures studied were: 20, 30, 40, 50, 60, 70, 80, and 100 mm Hg. Poststorage recovery of function was assessed with 30 min of working reperfusion. Control function of the unstored heart was: aortic flow (AF), 51.3 ± 2.2 ml/min; coronary flow (CF), 25.8 ± 1.2 ml/min; cardiac output (CO), 77.7 ± 2.3 ml/min; work, 92.0 ± 4.9 g-m/min; and coronary vascular resistance (CVR), 2.64 ± .21 mm Hg-min/ml. Functional return in the 30, 40, 50, 60, 70, and 80 mm Hg groups was similar. Recovery in a representative group (60 mm Hg) was: AF, 52 ± 3%; CF, 41 ± 2%; CO, 48 ± 3%; work, 42 ± 3%; and CVR, 225 ± 10% of the control. The total IP volume in this group was 71.0 ± 1.7 ml; total lactate dehydrogenase (LDH) release during IP was 8.62 ± .37 units/g dry; and end-storage tissue lactate was 52.6 ± 6.4 μmole/g dry. As IP pressure decreased to 20 mm Hg, cardiac functional recovery declined significantly to AF, 35 ± 6%; CF, 33 ± 2%; CO, 34 ± 5%; and work, 27 ± 4% of control (P< .05 vs. 60 mm Hg group). The total IP volume decreased to 10.1 ± .9 ml, tissue lactate content rose to 87.1 ± 10.9 (P< .05 vs. 60 mm Hg group), but LDH release fell to 5.59 ± .46 (P< .05 vs. 60 and 100 mm Hg groups). When IP pressure increased to 100 mm Hg, cardiac function was depressed with AF recovered to 25 ± 3%; CF, 30 ± 3%; CO, 26 ± 3%; work, 21 ± 3%; and CVR, 294 ± 26% of control (P< .05 vs. 60 mm Hg group). IP volume increased to 100.7 ± 2.4 ml; total LDH release increased to 19.1 ± 1.2 (P< .05 vs. 60 mm Hg group), although tissue lactate (58.9 ± 3.9) was not different from the 60 mm Hg group. End-storage tissue wet/dry weight ratio and myocardial adenosine triphosphate content were not different among the 20, 60, and 100 mm Hg groups. In conclusion, IP has a broad pressure optimum ranging from 30 to 80 mm Hg for 24-hr hypothermic preservation of the rat cardiac explant.