Effect of metoprolol in postinfarction patients with increased heart size

Mortality was analysed in relation to clinical and radiological signs of left ventricular failure in a double-blind randomized comparison of 154 post-myocardial infarction patients assigned to metoprolol (100 mg b.i.d.) and 147 patients assigned to placebo treatment. The maximal respiratory rate in the coronary care unit and the relative heart size measured by chest X-ray examination prior to discharge from hospital were used for evaluation of myocardial function. In the placebo group mortality was higher in those with elevated maximal respiratory rate (11% vs. 27%, P less than 0.05) and in those with larger hearts (8% vs. 33%, P less than 0.001). No increase in mortality in patients with findings of left ventricular dysfunction was found in the metoprolol treated group. This was not due to an excess mortality in patients with preserved left ventricular function, but rather due to a reduction in mortality among patients with impaired left ventricular function. In patients with relative heart sizes greater than 460 ml m-2 (= median), mortality was higher in the placebo treated patients as compared to metoprolol treated patients (33% vs 16%, P less than 0.05). During the three year follow-up, repeat chest X-ray examination showed similar heart sizes in the two treatment groups. Furthermore, treatment with digitalis and diuretics were similar in the two treatment groups although more patients in the metoprolol group were withdrawn due to uncontrolled left ventricular heart failure (7 vs 1, P less than 0.05). We conclude that elevated maximal respiratory rate in the coronary care unit and heart enlargement on a pre-discharge chest X-ray, indicate a worsened prognosis. This excess mortality is reduced by metoprolol treatment during a three year follow-up.