Abstract

Metoprolol (200 mg daily) and propranolol (160 mg daily) were each given for one week to 11 normal subjects. The order of administration was randomized and not known to us during the study. Each period of treatment with active drug was followed by one week during which placebo tablets were taken. M-mode echocardiograms and blood pressure were recorded before entry to the trial, twice during each week of treatment with metoprolol or propranolol, and daily for three days and on the seventh day after stopping the drugs. Septal and posterior wall endocardial echoes were traced with an X-Y digitiser and left ventricular minor axis dimensions derived every 10 ms with a minicomputer. Both drugs reduced heart rate, cardiac output, and blood pressure. Systemic vascular resistance was increased significantly by propranolol, and with both agents was inversely related to heart rate, cardiac output, left ventricular diastolic dimension, and indices of contractility.