CORONARY AUTOREGULATION PROTECTS AGAINST HARMFUL EFFECTS OF COMMONLY USED CARDIOPLEGIA DELIVERY PRESSURE

Objective. Hearts or parts of hearts are often ischemic prior to infus ion of the cardioplegic solution and have a more or less dilated coron ary bed. We made an investigation whether coronary dilation just prior to induction of cardiac arrest by aortic clamping and infusion of cry stalloid cardioplegic solution would influence cardioprotection. Metho ds. Isolated buffer-perfused rat hearts (100 cm H2O pressure (= 73.5 m mHg), 37 degrees C) were used, After a stabilization period the perfus ion of 8 rats (group 1) was stopped and the hearts arrested with 5 ml CS (100 cm H2O, 12 degrees C). Equal amounts of cardioplegic solution were then delivered every 20 minutes for the entire 31/2 hour hypother mic ischemic period. Following ischemia the hearts were reperfused for 60 minutes, In group 2 (n = 8) 1 ml 10(-2) mmol Papaverine was given into the aortic root just prior to the first cardioplegic solution inf usion in order to induce coronary vasodilation. The procedure was iden tical in the two groups during ischemia and reperfusion. Results. Duri ng the ischemic period coronary resistance increased in group 2. Durin g reperfusion group had lower coronary flow (P = 0.001), left ventricl e developed pressure (P = 0.002) and a higher creatine kinase release (P = 0.003) than group 1 hearts, Group 2 also had a lower adenosine-tr iphosphate (6.51 +/- 0.40 mu mol . g(-1) and 14.03 +/- 0.59 mu mol . g (-1). respectively, P = 0.011), creatine phosphate (24.70 +/- 1.02 mu mol . g(-1) and 36.50 +/- 1.31 mu mol . g(-1), respectively, P = 0.020 ) and a larger fall in dry/wet-weight ratio (1.7 +/- 0.4 and 0.8 +/- 0 .5, respectively, P = 0.043). Conclusions. Vasodilation (i.e. ischemia ) just prior to infusion of crystalloid cardioplegic solution may impa ir myocardial protection even when the cardioplegic solution is delive red at a relatively low and presumably safe pressure.