24-HOUR INTERMITTENT PERFUSION STORAGE OF THE ISOLATED RAT-HEART .2. PERFUSION-PRESSURE AND FUNCTIONAL PRESERVATION

This study investigated the effect of intermittent perfusion (IP) pres sures on functional preservation of the cold-stored isolated rat heart . The heart was flushed with cardioplegic solution #11 with ethylene d iaminetetraacetic acid and 2, 3-butanedione monoxime (CP-11EB), and st ored at 0 degrees C for 24 hr. During storage, the heart was intermitt ently perfused for 3 min at 10 and 17 hr of storage with 25 degrees 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 h eart was: aortic flow (AF), 51.3 +/- 2.2 ml/min; coronary flow (CF), 2 5.8 +/- 1.2 ml/min; cardiac output (GO), 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 m m 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%; a nd 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 mu mole/g dry. As IP pressure decreased to 20 mm Hg, cardia c functional recovery declined significantly to AF, 35 +/- 6%; CF, 33 +/- 2%; CO, 34 +/- 5%; and work, 27 +/- 4% of control (P <.05 vs. 60 m m Hg group). The total IP volume decreased to 10.1 +/- .9 ml, tissue l actate 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 depress ed 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 grou p). IF volume increased to 100.7 +/- 2.4 ml; total LDH release increas ed to 19.1 +/- 1.2 (P <.05 vs. 60 mm Hg group), although tissue lactat e (58.9 +/- 3.9) was not different from the 60 mm Hg group. End-storag e tissue wet/dry weight ratio and myocardial adenosine triphosphate co ntent were not different among the 20, 60, and 100 mm Hg groups. In co nclusion, IP has a broad pressure optimum ranging from 30 to 80 mm Hg for 24-hr hypothermic preservation of the rat cardiac explant. (C) 199 6 Academic Press, Inc.