Inability of Left Ventricular Decompression to Limit Myocardial Infarct Size

Abstract

Although the restoration of blood flow is the treatment of choice for myocardial ischemia, uncontrolled reperfusion itself may be injurious. We wished to determine whether unloading the beating left ventricle at the onset of reperfusion could limit myocardial infarct size. We studied isolated rabbit hearts, perfused with blood from a support rabbit and electrically paced at 200 beats/min. Rabbits were chosen because of the lack of preformed coronary collateral vessels. Four groups of rabbits were studied; all hearts underwent 60-min coronary artery occlusion and 2 h of reperfusion. The experimental conditions were as follows: In group 1, hearts contracted isovolumetrically on a fluid-filled balloon in the left ventricle during both occlusion and reperfusion. In group 2, the balloon was present only during occlusion, and the heart was vented during reperfusion. Group 3 hearts were vented during both occlusion and developed pressure during reperfusion. Hearts in group 4 were vented during both occlusion and reperfusion. Total coronary flow was measured by timed collection of effluent blood. Infarct size was assessed by the triphenyl tetrazolium method, and expressed as a percent of the area at risk, as determined with fluorescent particles. Perfusion pressure and coronary flow were not different between groups.