Consistency of the beneficial effect of metoprolol succinate extended release across a wide range dose of angiotensin-converting enzyme inhibitors and digitalis

BACKGROUND: The effects of beta-blockade with different extent of angiotensin-converting enzyme inhibitors (ACEI) and digitalization are unknown. To assess the effect of metoprolol succinate controlled release/extended release (CR/XL) combined with high versus low doses of ACEI and digitalis, we analyzed data from The Metoprolol CR/XL Randomized Intervention Trial in Chronic Heart Failure (MERIT-HF) in which patients with heart failure and left ventricular ejection fraction < or =40% were randomized to metoprolol CR/XL versus placebo. METHODS AND RESULTS: Outcome was analyzed separately for those on a low dose (< or =median) of the ACEI or digitalis versus high dose (> median). The mean dose of ACEI in the high-dose group (n = 1457) was 3 times higher than that in the low-dose group (n = 2094). Mortality was reduced to a similar extent in the high- and low-dose ACEI subgroups (RR = .69 versus .64, respectively). Corresponding figures for combined mortality/all hospitalization and for mortality/hospitalization for heart failure were .85 versus .83, and .70 versus .68, respectively. Likewise, reduction in total mortality with metoprolol CR/XL was similar in patients receiving no digitalis (n = 1447; RR = .56), low dose (n = 1122; RR = .71), or high dose (n = 1421; RR = .71). CONCLUSION: This analysis of MERIT-HF demonstrates consistent and similar improvement in outcome of patients receiving metoprolol CR/XL when combined with either a high or low dose of an ACEI or digitalis, or no digitalis at all. Thus regardless of ACEI and digitalis dose and whether patients are treated with digitalis or not, it is very important to add a beta-blocker to the existing heart failure therapy. beta-blockers should not be withheld until target doses of ACEI have been achieved.