Effects of metabolic stimulation on cardiac allograft recovery

Background. We previously demonstrated that continuous perfusion of cardiac allografts during hypothermic storage with donor blood harvested at the time of organ retrieval improves myocardial recovery after transplantation. However, myocardial metabolism and function remain depressed compared to base line values. This study evaluated the use of a continuous infusion of donor blood enhanced with insulin to augment aerobic myocardial metabolism during and after hypothermic storage. Methods. Yorkshire pigs (45 to 50 kg) were used to perform 14 orthotopic cardiac transplants using either continuous perfusion with donor blood (blood group, N = 7) or perfusion with donor blood enhanced with 10 IU/L insulin (insulin group, N = 7). After heparinization, hypothermic (4°C) cardioplegic arrest, and donor heart extraction, donor blood (2844 ± 210 mL) was harvested in both groups and perfused at room temperature (20°C) at a pressure of 60 mm Hg for 3 hours. Blood cardioplegia was delivered after each anastomosis in both groups and arterial and coronary sinus blood samples were obtained to examine myocardial metabolism. A Millar micromanometer was used to measure left ventricular developed pressure and the rate–pressure product at varying preloads. Results. There were no differences in either myocardial lactate or acid release between the two groups. Hearts in the insulin group displayed higher myocardial oxygen extraction than those in the blood group. The recovery of developed pressure was higher in the insulin group compared to the blood group (91% ± 19% vs 73% ± 2%, p = 0.04). Conclusions. In this model, continuous perfusion of cardiac allografts with donor blood and insulin preserves myocardial metabolism during hypothermic storage and improves metabolic and functional recovery after orthotopic cardiac transplantation.