Reduction in infarct size following experimental coronary occlusion by administration of verapamil.

The effect of verapamil, a calcium antagonist and antiarrhythmic and anti-anginal actions, were studied on the size of infarct in open-chest anesthetized dogs with left anterior descending coronary artery occlusion. Hemodyamic functions were monitored by standard techniques, and infarct size was assessed by epicardial electrocardiography. Myocardial blood flow was measured by radioactive microspheres, and regional metabolism was studied by measuring lactate concentration in the venous drainage of the ischemic myocardium. Verapamil produced a significant reduction to ST segment elevation in the epicardial electrocardiogram and prevented the hemodynamic deterioration seen in the control animals in which ST segment elevation persisted. The drug had no effect on either total collateral blood flow or on the relative distribution of flow to the inner and outer halves of the ventricular wall. No significant differences were found between the levels of coronary venous lactate in the control animals and those in the verapamil-treated group. The results raise the possibility that the apparent protective effect of verapamil in myocardial ischemia may be due to its electrophysiological action on the cardiac membrane in relation to its calcium-antagonistic properites in excitable tissues.