NEW EXPERIMENTAL-TECHNIQUE TO STUDY BLOOD CARDIOPLEGIA IN THE ISOLATED, PERFUSED RAT-HEART

Blood cardioplegia has been extensively studied clinically and in the large animal experimental model. We describe here a modification of th e original Langendorff technique to study continuous warm blood cardio plegia in the isolated, perfused rat heart. The excised heart is mount ed on the perfusion apparatus and perfused with Krebs-Henseleit buffer . Prearrest hemodynamics are recorded. The shed blood in the mediastin al cavity (8 to 12 mL) is collected, filtered, and reconstituted into cardioplegic solution (hematocrit, 0.20; K+, 15 mmol/L). Hearts are ar rested and maintained at 37-degrees-C by continuous recirculation of b lood cardioplegia for 1 hour. The blood cardioplegia system consists o f a Silastic tubing oxygenator, peristaltic pump, and two filters (40 mum pore size). The heart is reperfused with Krebs-Henseleit solution, and postarrest hemodynamics are recorded. Percentage recovery of peak left ventricular pressure, heart rate, and coronary flow were 98.5 +/ - 3.1, 102 +/- 4.2, and 98.5 +/- 4.5 (mean +/- standard error of the m ean; n = 6), respectively. Myocardial oxygen consumption during arrest was 57 muL . min-1 . g-1 dry wt, which is 10% of the myocardial oxyge n consumption of a beating heart in in-vivo and ex-vivo models. These results suggest the feasibility of studying blood cardioplegia in the isolated, perfused rat heart model under controlled conditions. Contin uous warm blood cardioplegic arrest provided excellent myocardial prot ection for 1 hour in this model.