Effect of initial reperfusion temperature on myocardial preservation

The effect of initial postischemic reperfusion temperature on myocardial preservation was studied in the isolated working rat heart model. After baseline measurement of aortic flow rate, coronary flow rate, and heart rate, 40 hearts were subjected to 60 minutes of ischemic arrest at 15°C induced with a single dose of cold potassium cardioplegic solution. Hearts were then revived with a 10 minute period of nonworking reperfusion at 28°, 31°, 34°, or 37° C (10 hearts each), followed by 5 minutes of nonworking reperfusion at normothermia, followed by 30 minutes of working perfusion. Repeat measurements of function were obtained and postischemic release of creatine kinase into coronary effluent was determined. Recovery of aortic flow was significantly reduced at lower initial reperfusion temperatures (75% at 28°C versus 88% at 37°C) and the effect was approximately linear throughout the range studied (p < 0.05). Release of creatine kinase into coronary effluent was greater at lower initial reperfusion temperatures (421 ImU/min/gm wet weight at 28°C versus 115 ImU/min/gm wet weight at 37°C), also in a linear manner (p < 0.05). In this model, initial postischemic hypothermic reperfusion is deleterious to cellular integrity and functional recovery of the preserved myocardium. Studies in higher animals and humans are warranted to further evaluate the effect of initial reperfusion temperature on myocardial preservation.