Reduction of the size of acute, experimental myocardial infarction by Verapamil

The effect of 0.1 mg/kg Verapamil on the extent of the ischemic area following ligation of a branch of the left descending coronary artery was studied in anesthetized open chest dogs. The sum of the ST-segment elevation during the entire period of occlusion in the epicardial ECG was 15 mV in control infarction compared to 9 mV (p smaller than 0.0005) when Verapamil was infused after ligation. Mean flow in the left descending coronary artery was reduced by coronary ligation alone on the average by 23%, but augmented by Verapamil for 5% above pre-occlusion control flow. Corresponding to the rise in the coronary flow and the drop in perfusion pressure under the influence of Verapamil, the increase of left coronary artery resistance induced by coronary occlusion was diminished. The positive effect of Verapamil on the size of myocardial infarction as estimated from the epicardial ST-segment changes is probably not induced by coronary vasodilatation, but by the Ca-antagonizing effect of this drug, as described by other authors.