Effect of infarct size limitation by propranolol on ventricular arrhythmias after myocardial infarction.

These experiments show that pretreatment with propranolol was able to achieve significant infarct size reduction in this particular animal model of LAD occlusion followed by reperfusion through a critical stenosis. Despite infarct size reduction, the propranolol pretreatment prolonged the time course of spontaneous ventricular arrhythmias after acute myocardial infarction in the conscious dog. In contrast to this, propranolol pretreatment did not appear to protect against inducible ventricular arrhythmias in the late postinfarction period in the conscious dog. While it is, of course, impossible to extrapolate the results of animal studies to the clinical situation, future clinical studies designed to limit infarct size by pharmacologic intervention should specifically address the question of electrophysiologic instability after myocardial infarction, both in the early and late phases. The possibility exists that pharmacologic limitation of infarct size may preserve viable but potentially jeopardized areas of myocardium, leaving the risk of subsequent malignant arrhythmias and sudden death.