alpha- and beta-blockade with labetalol in acute myocardial infarction.

On the hypothesis that the addition of alpha-blockade would mitigate the haemodynamic disadvantages of beta-blockade alone in the early stages of uncomplicated acute myocardial infarction, 15 patients were studied during the intravenous infusion of labetalol (0.5 mg/kg/h). The mean systemic arterial pressure was reduced by an average of 15 mm Hg. In the nine patients haemodynamically evaluated, the cardiac output (thermal dilution) was reduced without change in the heart rate or left heart filling pressure (pulmonary artery occluded pressure); left ventricular stroke work was significantly decreased. The reduction in these major determinants of myocardial oxygen consumption suggests that the combination of alpha- and beta-blockade may be haemodynamically advantageous in normotensive patients in the early stages of uncomplicated acute myocardial infarction.