[Clinical study of the month. The MERIT-HF study]

MERIT-HF study was a multicenter, double-blind randomized placebo-controlled study which enrolled 3.991 class II-IV heart failure patients with a left ventricular ejection fraction < or = 40% who were already treated by optimal standard therapy (diuretic + ACE inhibitor or equivalent). Three thousand nine hundred ninety one patients were enrolled in the study: 2.001 received a placebo; 1.990 were assigned to metoprolol administration at the initial dose of 25 mg/day (12.5 mg for class III-IV patients) and progressively increased to a maximum daily dose of 200 mg. The study was prematurely stopped because, after an observation period of 3.980 patients x years, it demonstrated a significant mortality reduction in the treated group. All cause mortality was reduced by 34% (7.2% per patient x year vs 11%). Sudden death mortality and mortality due to progression of heart failure were reduced by 41% and 49%, respectively.