Central haemodynamic effects of metoprolol early in acute myocardial infarction. A placebo controlled randomized study of patients with low heart rate

The central haemodynamic effects of metoprolol in patients withacute myocardiol infarction and with heart rate 65 beats min^–1have been investigated in a randomized double-blind trial. Theaim was to study the tolerance in this selected patient groupand to assess possible differences in haemodynamic responseamongst patients with initially higher heart rates. Exclusioncriteria were: treatment with beta blockers; heart rate 65beats min^–1 systolic blood pressure 110 mmHg; and physicalsigns of serious heart failure. Following pulmonary artery catheterization,22 patients were randomized to metoprolol 15 mg i. v. + 50 mgq.i.d. orally ( N = 12) or placebo (N = 10). Central pressuresand cardiac output were recorded before and during the 24 hoursafter drug administration. There was a significant fall in heartrate, cardiac index, rate pressure product and stroke work indexof 10–20% in the metoprolol, compared with the placebogroup. The differences were most pronounced immediately afterthe metoprolol injection. The pulmonary artery capillary wedgepressure was not significantly changed. The overall haemodynamicresponse to metoprolol was similar to that reported in patientswith acute myocardial infarction and heart rate above 65 beatsmin^–1 Tolerance was good.