Adrenergic beta-blocking agents in congestive heart failure due to idiopathic dilated cardiomyopathy

The use of Beta-blockers for treatment of chronic heart failure due to idiopathic dilated cardiomyopathy has now begun to be accepted among cardiologists after having been used sporadically for 19 years. Pooled data from several minor controlled trials performed during the last 13 years which have shown consistent improvement of myocardial function, specifically in patients with idiopathic dilated cardiomyopathy, have recently been confirmed by two major trials using the selective beta-blockers metoprolol (MDC trial) and bisoprolol (CIBIS trial). There was a decrease of 34% in the combined number of deaths and patients needing a heart transplantation (P = 0.058) in the MDC trial. Bisoprolol, as well as reducing the overall mortality significantly, was found, in a retrospective subgroup analysis, to reduce mortality in idiopathic dilated cardiomyopathy. The MDC trial showed improvement in ejection fraction by 7 units compared with placebo and 13 units compared with baseline after 12 months treatment (P < 0.0001). There was also an increase in exercise time compared with placebo at 12 months follow-up. There was a 39% reduction in the number of readmissions to hospital due to heart failure and arrhythmias (P < 0.04) and a 32% reduction in the CIBIS trial (P < 0.01). Possible mechanisms for improvement after beta-blockers are improvement in myocardial energetic balance, protection against calcium overload or normalization of myocardial catecholamine kinetics. The role of upregulation of beta-adrenergic receptors remains controversial since this could not be seen in the action of all beta-blockers. The question of whether mortality can be reduced remains unsolved and will require large prospective trials which are now in progress.