Improvement in symptoms and exercise tolerance by metoprolol in patients with dilated cardiomyopathy: a double-blind, randomized, placebo-controlled trial.

Abstract

It has been suspected that the increased sympathetic activity seen in patients with chronic congestive heart failure from dilated cardiomyopathy may be harmful. We therefore tested the long-term effect of metoprolol on eight patients in a double-blind, randomized protocol and 12 patients in an unblinded, crossover protocol who were treated for 12 months (range 10 to 24), and compared them with 16 similar subjects who were treated with placebo for 10 months (range 6 to 12) in a double-blind, randomized protocol. Patients were followed by serial clinical assessment, treadmill testing, radionuclide ventriculography, and echocardiography. Metoprolol-treated patients had an improvement in mean exercise capacity by 3 mets (p less than .0001) while experiencing a significant improvement in functional classification (p less than .001) during both the double-blind and open-label crossover studies and had an improved ejection fraction during the double-blind study (p less than .02). These improvements were not seen in matched control subjects receiving placebo. Seven of 20 patients receiving long-term metoprolol therapy had resolution of nearly all symptoms of heart failure, doubled their exercise capacity, and had progressive improvement in resting radionuclide left ventricular ejection fraction (12.6 +/- 3% to 26.9 +/- 6%) and echocardiographic left ventricular end-diastolic dimension (7.7 +/- 0.5 to 6.5 +/- 0.5 cm). Only one of 21 patients treated was intolerant of metoprolol. We conclude that metoprolol can be given safely to a select group of patients with dilated cardiomyopathy in doses that substantially reduce both resting and exercise heart rates. Long-term beta-blockade improved functional class and exercise capacity in 14 of 20 patients while producing an exceptional clinical response in seven that was accompanied by improved resting parameters of left ventricular function.