[Use of beta-blockers in the acute phase of myocardial infarction]

Several experimental studies have demonstrated that the early administration of beta blockers in the setting of an acute myocardial infarction (in the first six hours) tended to diminish the area of myocardial necrosis. Numerous attempts to limit infarct size with beta blockers have occurred over the past ten years. Without a reliable and reproducible method to measure necrosed tissue, it has been difficult to evaluate the effectiveness of this therapy. Presently available studies have demonstrated, however, that beta blockers are well tolerated in the setting of an acute infarction as long as none of the usual contraindications are present. The majority (but not all) of these studies indicated improvement in parameters used to determine the amount of tissue necrosis and a tendency (not always significant due to the small numbers studied) to decrease morbidity and mortality during hospitalization. One study using metoprolol administered during the acute phase and continued during the first three months demonstrated a significant decrease in mortality. The results of this study are very demonstrative, nevertheless, once the acute necrotic phase is over, it is difficult to ascertain whether diminished tissue necrosis or the preventive effect of beta blockers is responsible for these findings until a recurrence or sudden death occurs.