Effects of verapamil on the acute experimental myocardial ischemia

The hemodynamic effects of verapamil in conditions of myocardial ischemia and its influence on the atrio-ventricular conduction were investigated in 13 dogs with transient repeated occlusions of the anterior descending coronary artery. Verapamil 0.25 mg/kg was administered after control determinations of heart rate, LV dp/dt, systolic and diastolic arterial pressure and the mean sum of S--T segment elevations recorded by means of 9 epicardial electrodes. Comparison of the differences between the control data and those after occlusion, on the one hand, and those before and after occlusion + verapamil, on the other hand, showed that the drug did not induce significant hemodynamic changes. Arterial pressure was slightly lowered; the increase of LV dp/dt noted after occlusion without verapamil did not occur any more and the S-T segment and T wave disturbances were also less marked, suggesting a protective effect on the ischemic lesion. Larger doses of verapamil (0.50-0.75 mg/kg) induced second and third degree A-V blocks in three animals. These effects could be controlled in two animals by previous or subsequent administration of Carbocromen.