Beta-adrenergic blockade in dilated cardiomyopathy, ischemic cardiomyopathy, and other secondary cardiomyopathies.

Beta-blockers were initially given to patients with chronic heart failure due to ischemic heart disease and resting tachycardia. The prompt effect on severe backward heart failure was directly associated with an immediate fall in heart rate. This observation led to long-term administration to patients with idiopathic dilated cardiomyopathy and, later, to patients with ischemic cardiomyopathy and secondary cardiomyopathies as well. Due to marked down-regulation of beta receptors, patients with heart failure are extremely sensitive to beta blockade. A test dose of metoprolol 5 mg b.i.d. for 2 days is recommended to select patients for long-term beta-blockade, followed by careful titration with increment in dose over 6 weeks. One important effect of beta-blockade in the early phase of treatment is a reduction in the myocardial energy demand early after the onset of long-term treatment. After 1 month of treatment with beta-blockers, marked improvement of diastolic function is observed. This effect might be attributed to inhibition of calcium overload. After 3 months of treatment, an increase in ejection fraction can be observed, which might be attributed to upregulation of beta receptors. The withdrawal of long-term treatment was followed by a deterioration of heart function in 61% of patients and improvement was seen after reinstitution of beta-blockade. There was an increase in cardiac index and stroke work index at rest as well as during supine exercise. A marked fall in left ventricular filling pressure at rest and unchanged filling pressure during supine exercise was noted, while exercise capacity increased by 25%. A similar pattern was seen in patients with ischemic cardiomyopathies and other secondary cardiomyopathies. However, the increase in ejection fraction in the ischemic cardiomyopathy group was lower (0.06) compared to the groups with dilated cardiomyopathy and other secondary cardiomyopathies (0.18).