Treatment of cardiac myopathies with beta blockers. What do we know, where do we go from here?

The increase in sympathetic nervous system activity noted in heart failure of several etiologies has beneficial effects in the short term; in the long term, though, it may be detrimental. This provides a rationale for use of beta-blocker therapy in patients with cardiac myopathies of various etiologies. Postinfarction trials in patients with ischemic heart disease have suggested that beta blockade provides a substantial mortality benefit, and beta blockers are accepted as first-line therapy for hypertrophic cardiomyopathy. The use of beta-blocking drugs for dilated cardiomyopathy (DCM), however, is currently investigational. Early trials reporting benefits in functional class, exercise capacity, and myocardial function stimulated further interest in this application of beta blockade. Recent studies comparing metoprolol with placebo or standard treatment have shown promising improvements in functional class and exercise capacity. The patients who will benefit most from beta-blocker therapy in DCM may be those with a high resting heart rate and a short duration of symptoms and, perhaps, feminine gender. Marked structural abnormality on cardiac biopsy (eg, fibrosis) may suggest a poor response to treatment. A multicenter controlled study of metoprolol in dilated cardiomyopathy is in progress. If the outcome is favorable, beta-blocker therapy in DCM may become an accepted, rather than an experimental, treatment.