Effect of propranolol on experimental periinfarction block and myocardial ischemia.

The effects of propranolol on periinfarction block, myocardial ischemic injury and left ventricular performance following anterior descending coronary artery occlusion were studied. Experiments were made in 14 dogs anesthetized with pentobarbital sodium. Two minutes of reversible myocardial ischemia was induced by occlusion of descending left coronary artery. The severity of myocardial ischemia estimated by summing S-T segment elevation (sigma ST) from epicardial ECG mapping, heart rate, femoral arterial pressure and left ventricular (LV) dp/dt was determined before, during coronary occlusion alone and following propranolol infusion (0.25 mg/Kg) and coronary occlusion. Periinfarction block aspects on epicardial ECG appeared in four dogs following five repeated coronary occlusions. Propranolol infusion before coronary occlusion prevented the periinfarction block in every animal. The decrease of myocardial ischemia (sigma ST elevation), heart rate, arterial blood pressure and LV dp/dt following propranolol and coronary occlusion might be partly due to the beneficial effect of this drug on periinfarction block.