Effect of reperfusion temperature and pressure on the functional and metabolic recovery of preserved hearts.

Reperfusion conditions significantly affect recovery following global myocardial ischemia. Using an isolated dog heart model, we investigated the effect of initial (first 10 minutes) reperfusion temperature and pressure on the metabolic and functional recovery of the preserved heart. Four groups of five or six dogs each underwent 2 hours of ischemic cardioplegic arrest at 15 degrees C following single-dose crystalloid cardioplegia. Hearts were initially reperfused at 37 degrees C (high temperature) or 28 degrees C (low temperature) and at 50 mm Hg (low pressure) or 80 mm Hg (high pressure), giving four groups: (1) high-temperature, high-pressure; (2) high-temperature, low-pressure; (3) low-temperature, high-pressure; and (4) low-temperature, low-pressure. Septal temperatures were continuously recorded. Ventricular function curves 1 and 2 hours following reperfusion were significantly depressed in the high-temperature, high-pressure group (70%, p less than 0.01, and 83%, p less than 0.02) and the low-temperature, high-pressure group (78%, p less than 0.03, and 85%, p less than 0.03) but were normal in the low-temperature, low-pressure and the high-temperature, low-pressure groups. All groups showed edema 1/2 hour after reperfusion as measured by water and sodium content in myocardial biopsy specimens but only the high-temperature, high-pressure and the low-temperature, high-pressure groups showed persistent edema at 3 hours (3.95 +/- 0.2 ml H2O/gm dry weight, p less than 0.03 and 3.99 +/- 0.16 ml/gm, p less than 0.02, respectively). Only low-temperature, high-pressure reperfusion resulted in statistically significant reductions in adenosine triphosphate (ATP) 1/2 hour and 2 hours following reperfusion (a 15% reduction from baseline). Maximum rewarming rates were measured for each group. High-temperature, high-pressure = 2 degrees C per second; low-temperature, high-pressure = 1 degree C per second; high-temperature, low-pressure = 0.75 degrees C per second; and low-temperature, low-pressure = 0.4 degrees C per second. High-pressure reperfusion following global myocardial ischemia results in rapid rewarming and is associated with prolonged myocardial edema, depressed ATP levels, and delayed functional recovery. Therefore, we employ 10 minutes of low-pressure reperfusion in our patients undergoing potassium cardioplegic arrest.