The results of the US and Australia-New Zealand trials were as follows:

Slowing Progression of Heart Failure: One US multicenter study (366 subjects) had as its primary end point the sum of cardiovascular mortality, cardiovascular hospitalization, and sustained increase in heart failure medications. Heart failure progression was reduced, during an average follow-up of 7 months, by 48% (p = 0.008).

In the Australia-New Zealand study, death and total hospitalizations were reduced by about 25% over 18 to 24 months. In the 3 largest US studies, death and total hospitalizations were reduced by 19%, 39%, and 49%, nominally statistically significant in the last 2 studies. The Australia-New Zealand results were statistically borderline.

Functional Measures: None of the multicenter studies had NYHA classification as a primary end point, but all such studies had it as a secondary end point. There was at least a trend toward improvement in NYHA class in all studies. Exercise tolerance was the primary end point in 3 studies; in none was a statistically significant effect found.

Subjective Measures: Health-related quality of life, as measured with a standard questionnaire (a primary end point in 1 study), was unaffected by carvedilol. However, patients' and investigators' global assessments showed significant improvement in most studies.

Mortality: Death was not a pre-specified end point in any study, but was analyzed in all studies. Overall, in these 4 US trials, mortality was reduced, nominally significantly so in 2 studies.

COMET Trial: In this double-blind trial, 3,029 patients with NYHA class II-IV heart failure (left ventricular ejection fraction ≤35%) were randomized to receive either carvedilol (target dose: 25 mg twice daily) or immediate-release metoprolol tartrate (target dose: 50 mg twice daily). The mean age of the patients was approximately 62 years, 80% were males, and the mean left ventricular ejection fraction at baseline was 26%. Approximately 96% of the patients had NYHA class II or III heart failure. Concomitant treatment included diuretics (99%), ACE inhibitors (91%), digitalis (59%), aldosterone antagonists (11%), and "statin" lipid-lowering agents (21%). The mean duration of follow-up was 4.8 years. The mean dose of carvedilol was 42 mg per day.

The study had 2 primary end points: All-cause mortality and the composite of death plus hospitalization for any reason. The results of COMET are presented in Table 3 below. All-cause mortality carried most of the statistical weight and was the primary determinant of the study size. All-cause mortality was 34% in the patients treated with carvedilol and was 40% in the immediate-release metoprolol group (p = 0.0017; hazard ratio = 0.83, 95%CI 0.74-0.93). The effect on mortality was primarily due to a reduction in cardiovascular death. The difference between the 2 groups with respect to the composite end point was not significant (p = 0.122). The estimated mean survival was 8.0 years with carvedilol and 6.6 years with immediate-release metoprolol.

Table 3. Results of COMET

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