The effect of superoxide dismutase and catalase on the extended preservation of the ex vivo heart for transplantation

The applicability of heart transplantation remains limited in part by the inability to preserve the excised heart for long periods of time. Free radical scavengers have been shown to protect the anoxic myocardium by preventing damage to the cell membrane and may, therefore, be effective in extending successful preservation of donor hearts. We perfused 10 sheep hearts for 8 hours in an ex vivo perfusion system. The effect of superoxide dismutase combined with catalase, 60,000 units/L, was studied in five sheep, and five received placebo. Control determinations and determinations after 8 hours of preservation were obtained with the heart perfused with autologous blood at 37°C at an aortic perfusion pressure of 60 mm Hg and flow of 180 to 200 ml/min. After control readings, the hearts were arrested and perfused with a cold (6° to 8°C) oxygenated buffered crystalloid solution with or without superoxide dismutase and catalase at a perfusion pressure of 30 cm H₂O for 8 hours. Left and right ventricular compliance was measured sequentially with separate intraventricular balloons. After 8 hours of ex vivo preservation, heart receiving superoxide dismutase and catalase had significantly better left and right ventricular performance, higher myocardial oxygen consumption, and lower lactate production than the control group. The hearts preserved with superoxide dismutase and catalase showed significantly better left and right ventricular compliance, much less increase in heart weight, and no change in the diastolic pressures. The results suggest that superoxide dismutase with catalase may be effective in extending ex vivo preservation of hearts for cardiac transplantation.