Failure of intravenous pindolol to reduce the hemodynamic determinants of myocardial oxygen demand or enzymatically determined infarct size in acute myocardial infarction.

Pindolol, a beta blocker with intrinsic sympathomimetic activity, was investigated in a randomised controlled trial of 100 patients presenting within 12 hours of uncomplicated acute myocardial infarction. Pindolol was given intravenously for 24 hours and orally for 48 hours to achieve serum levels above 10 ng/ml. Heart rate and arterial pressure, both systolic and diastolic, fell to a similar degree in actively treated and control patients. There was no significant difference between systolic blood pressure-heart rate product in actively treated and control patients during the first 72 hours of therapy. There was no increased incidence of cardiac failure, bradycardia, or AV conduction disturbance among pindolol-treated patients. Infarct size estimated from cumulative enzyme release did not differ significantly from controls regardless of whether pindolol was given within four hours or between four and 12 hours of symptom onset. However, fewer patients given pindolol within four hours required morphine. Use of pindolol during the acute phase of myocardial infarction did not appear to modify clinical course, hemodynamic determinants of myocardial oxygen demand, or enzymatically determined infarct size.