Early studies with selective beta blockers, such as bisoprolol and metoprolol XL, and with nonselective beta blockers, such as carvedilol, have demonstrated survival benefit in patients with congestive heart failure. A more recent trial of bucindolol that did not show a survival benefit suggested that not all anti-adrenergic agents have the same effect. Another study, the Carvedilol or Metoprolol European Trial, currently is comparing mortality and morbidity benefits of carvedilol and metoprolol in patients with moderate and severe congestive heart failure. Until this study is complete, treatment decisions must be based on smaller comparison studies. Rajput and associates reviewed six small studies comparing the efficacies of carvedilol and metoprolol in patients with congestive heart failure and decreased left ventricular function.

In three studies, both drugs significantly improved patients' New York Heart Association class, although there was no significant difference in class improvement between the comparison groups. This functional improvement was associated with improved myocardial contractility. Two studies with longer follow-up periods showed a greater improvement in ejection fraction in patients who took carvedilol. In three of the six studies, patients who took carvedilol for more than six months had a greater increase in left ventricular ejection fraction and a decrease in left ventricular chamber size. Cardiac response to exercise improved more in patients receiving carvedilol therapy.

The authors conclude that although both agents improve cardiac remodeling in patients with congestive heart failure, carvedilol provides superior resolution of left ventricular fraction. Patients who do not respond to metoprolol may improve when switched to carvedilol.