Clinical studies on beta blockers and heart failure preceding the MERIT-HF trial

With greater understanding of the impact of neuroendocrine stimulation on the adverse outcomes of heart failure, especially lethal arrhythmias and sudden cardiac death, focus has returned to the potential benefits of beta-adrenergic blockade. In patients with myocardial infarction and left ventricular (LV) dysfunction, particularly those prone to life-threatening arrhythmias, beta-blocker therapy has been associated with a lower incidence of arrhythmias and improved survival. Even in the absence of angiotensin-converting enzyme (ACE) inhibition, beta blockade has improved cardiac function and LV contractility in nonischemic heart failure, leading to a decrease in LV end-diastolic pressure and improved clinical status. Both the Metoprolol in Dilated Cardiomyopathy (MDC) trial and the Cardiac Insufficiency Bisoprolol Study (CIBIS) found beta blockade to be associated with decreased mortality rates in patients with nonischemic heart failure. Of the 3 large randomized mortality trials now under way, the Metoprolol CR/XL Randomized Intervention Trial in Heart Failure (MERIT-HF) is specifically designed to investigate the effects of beta blockade on total mortality when used as an adjunct to ACE inhibition in patients with ischemic or nonischemic heart failure. Unresolved issues to be addressed include whether: (1) beta-blocker therapy in heart failure can improve survival and/or reduce the incidence of sudden cardiac death; (2) beta blockade is equally effective in ischemic and nonischemic heart failure; (3) any specific beta blocker may be better tolerated initially and cause fewer adverse effects; and (4) all beta blockers result in improved exercise tolerance and quality of life. (C) 1997 by Excerpta Medico, Inc.