Studies of the effects of ventricular fibrillation on the adequacy of regional myocardial flow: I. Electrical vs. spontaneous fibrillation

Abstract

This study compares the effects of spontaneous and electrically maintained ventricular fibrillation on the adequacy and distribution of regional myocardial flow and metabolism in nonhypertrophied normothermic hearts. With spontaneous fibrillation, the left ventricle consumes approximately 50 per cent more oxygen than the beating empty heart, the proportion of total left ventricular flow delivered to the subendocardium increases significantly (P < 0.01), and no deleterious effects on myocardial metabolism or function result. When the ventricular fibrillation is maintained electrically with a 60 cycle AC stimulus (1.5 to 4 v.) coronary flow becomes redistributed away from the left ventricular subendocardium, left ventricular oxygen consumption falls, biochemical evidence of left ventricular ischemia develops, and ventricular performance becomes impaired (P < 0.01). These studies suggest that left ventricular oxygen consumption fails to rise because the fibrillating stimulus impedes oxygen delivery to the left ventricular subendocardium and causes ischemia.