Background: Warm ischemia is a major cause of cardiac allograft failure in transplants from non-heart-beating donors. To minimize myocardial ischemia, we used a continuous myocardial perfusion technique for resuscitation of donor hearts. The purpose of the present study was to investigate an optimal duration of controlled initial reperfusion.
Methods: Cardiac arrest was induced by asphyxia in 18 donor pigs. The hearts were harvested 30 minutes after global warm ischemia. Continuous myocardial reperfusion was immediately commenced from the aortic root with blood cardioplegic solution (20 degrees C, 40 mm Hg) and then with oxygenated blood (20 degrees to 37 degrees C, 40 to 60 mm Hg). Animals were divided into three groups according to the duration of the initial reperfusion: group I = 5 minutes, group II = 20 minutes, and group III = 60 minutes. Orthotopic transplantation was performed while keeping the heart beating by continuous myocardial perfusion. Cardiac function was evaluated before anoxia and after transplantation. Lactate extractions were determined during reperfusion. Myocardial edema was assessed by heart weight and posterior wall thickness of the left ventricle.
Results: Recovery rates of cardiac function in group II hearts after transplantation were better than in groups I and III (cardiac output, 61% +/- 9% versus 41% +/- 5% versus 44% +/- 4%, respectively; p < 0.05; left ventricular end-systolic pressure-volume ratio, 64% +/- 8% versus 36% +/- 9% versus 42% +/- 6%, respectively; p < 0.05). Lactate extractions in groups II and III returned to 0 within 20 minutes of reperfusion. Myocardial edema after transplantation in group II hearts was less than in groups I and III.
Conclusions: The best recovery was observed in the non-beating donor hearts resuscitated by continuous myocardial perfusion when the initial controlled reperfusion with lukewarm blood cardioplegic solution at 40 mm Hg lasted for 20 minutes.