Intermittent Perfusion of Ischemic Myocardium

Intermittent restoration of coronary flow during ischemia reduced myocardial damage and improved recovery of function. The mechanisms of the protective effects of intermittent perfusion were investigated in isolated rat hearts. Ventricular function was assessed as the product of developed pressure (left ventricular systolic pressure minus end-diastolic pressure) and heart rate. Recovery of function was calculated by division of the product at the end of reperfusion by that before ischemia. After 40 minutes of sustained global ischemia, intracellular Na+ (Na;) increased from 11 to 74 ,umol/g dry wt. During 30 minutes of reperfusion, these hearts took up a large amount of 45Ca2' (10 ,umolUg dry wt), recovered only 24% of preischemic function, and had an increased left ventricular end-diastolic pressure (48 mm Hg). When the 40-minute period of ischemia was interrupted at 10-minute intervals by intermittent perfusion (three periods of 3 minutes) with either oxygenated or hypoxemic buffer, Na; increased to only 12 or 17 ,umol/g dry wt, and reperfusion resulted in much lower 45Ca21 uptake (0.5 and 0.5