Early and late effects of coronary artery occlusion on canine Purkinje fibers.

The electrophysiological characteristics of subendocardial Purkinje and myocardial cells were studied during acute (within 30 minutes) and chronic (after 10 days) phases of myocardial infarction. Endocardial Purkinje and myocardial electrograms were recorded in vivo with bipolar electrodes before and after occlusion of the anterior descending coronary artery. Also, intracellular and extracellular potentials were recorded in vitro from the endocardial surface of infarcted regions of hearts excised during the acute and chronic phases. In the acute phase, Purkinje and myocardial potentials within the ischemic zone deteriorated in vivo, but they were not markedly delayed. Intracellular recordings in vitro showed partial depolarization of both Purkinje and myocardial cells. In the chronic phase, extracellular and intracellular Purkinje potentials recorded in vivo and in vitro from the infarcted zone usually did not differ from normal. No myocardial potentials were recorded from the endocardial surface of the chronic infarcts. Thus, subendocardial Purkinje and myocardial cells are affected early in infarction, but many Purkinje cells survive and return to normal.