Hemodynamic Effects of the Cardioselective β‐Blocking Agent Metoprolol in Acute Myocardial Infarction

Abstract

Hemodynamic changes were studied in ten patients with uncomplicated transmural myocardial infection during 24 hours on β‐blockade. The cardloselective β‐adrenergic blocking drug metoprolol was injected (15 mg i.v.) within the first 24 hours after onset of chest pain and was followed by oral therapy (25–50 mg at 6‐hour intervals). There was a decrease in heart rate, systolic BP, and cardiac output, which was most marked after the injection. The stroke volume and diastolic BP for the whole group of patients remained unchanged. The pulmonary artery end diastolic pressure did not change significantly after the injection but a continuous fall was obtained in three out of four patients with initially elevated values. The preejection period, measured born the ECG and carotid pressure curve, was initially short and was prolonged in all patients after administration of the β‐blocking drug. It is concluded that the cardioselective β‐blocking drug metoprolol may be used in selected patients in the acute phase of myocardial infarction without danger of hemodynamic deterioration during the first 24 hours of therapy. The selection of patients can be based on clinical criteria. In this study signs of left heart failure, hypotension, poor peripheral circulation, bradycardia, and AV block were regarded as contraindications.