Recent studies have shown multiple benefits from beta-blocker therapy in some patients with congestive heart failure (CHF) who remain symptomatic despite triple therapy with digoxin, diuretics and angiotensin-converting enzyme inhibitors. Metoprolol was one of the earliest and most frequently studied beta blockers in patients with heart failure. It is a second-generation agent that is commonly used despite the fact that it has no vasodilating properties. Carvedilol, a third-generation beta blocker, is the only one of these agents labeled by the U.S. Food and Drug Administration specifically for the treatment of heart failure. Carvedilol has been shown to improve left ventricular ejection fraction and may reduce mortality. To date, there has been no direct prospective comparison of carvedilol with other beta blockers. Kukin and associates evaluated the effectiveness of carvedilol and metoprolol in treating patients with CHF.
Patients with a diagnosis of symptomatic, stable CHF were eligible for the study. Those whose condition was secondary to obstructive valvular disease, recent acute myocardial infarction or active angina were excluded from the study. Baseline vital signs and laboratory studies were obtained from all patients, and quality of life questionnaires and a heart failure symptom score checklist were completed for each patient. In addition, ejection fraction measurements were obtained and exercise tests were conducted on all patients. Those who met the study criteria were randomized to receive either carvedilol or metoprolol in addition to standard therapy for CHF. Both medications were started at a low dosage and titrated up slowly. The target dosage for both medications was 25 mg twice daily; in patients who weighed more than 187 lb (85 kg), the target dosage was 50 mg twice daily. After four and six months of continuous maintenance therapy, all baseline studies were repeated.
A total of 67 patients met the study criteria, with 30 assigned to the metoprolol group and 37 to the carvedilol group. Baseline characteristics were similar between groups. Target dosages were achieved in 83 percent of the metoprolol group and 81 percent of the carvedilol group. Overall, 53 patients showed significant but parallel improvements in all clinical and exercise parameters. Heart failure symptom scores improved in both groups. Ejection fraction measurements increased about 5 percent in both groups over a six-month period. However, patients receiving carvedilol experienced a greater decrease in heart rate.
The authors conclude that carvedilol and metoprolol appear to be equally effective in treating CHF and emphasize that the results of this study confirm that beta-blocker therapy should be continued in patients with CHF.