Combined administration of nitroglycerin and propranolol to patients with acute myocardial infarction

Hemodynamic effects of combined nitroglycerin and propranolol administration were investigated in patients with acute myocardial infarction. After nitroglycerin infusion decreased the mean arterial pressure by 20 mm Hg for one hour, nitroglycerin was continued, and patients were given 0.033 mg/kg of propranolol every five minutes for a total dose of 0.1 mg/kg, or until there was a decrease in heart rate to less than 60 beats/min, an increase in left ventricular filling pressure (LVFP) to greater than 15 mm Hg, or a decrease in systolic arterial pressure to less than 85 mm Hg. Seven of eight patients with initial LVFP less than or equal to 15 mm Hg and three of seven with initial LVFP greater than 15 mm Hg received 0.1 mg/kg of propranolol. Propranolol significantly decreased heart rate. Although pressure time/minute decreased significantly, the magnitude of its decrease was small, suggesting only a minimal effect on myocardial oxygen demands. The LVFP increased after giving propranolol but remained less than the control value. Simultaneous administration of nitroglycerin likely prevented further increases, since LVFP increased after cessation of nitroglycerin infusion, and three patients subsequently had pulmonary edema. Propranolol administration resulted in a significant increase in peripheral vascular resistance and a decrease in cardiac output.