Background: Guidelines recommend that patients with heart failure receive Î²-blockers in doses used in the trials that have proven their efficacy. Although the adverse effects of Î²-blockade are dose-related, it is unclear whether the benefits are.
Purpose: To determine whether the survival benefits of Î²-blockade in heart failure are associated with the magnitude of heart rate reduction or the Î²-blocker dose.
Data Sources: MEDLINE, EMBASE, CINAHL, SIGLE, Web of Science, and the Cochrane Central Register of Controlled Trials, supplemented by hand-searches of bibliographies.
Study Selection: Randomized, placebo-controlled heart failure trials that reported all-cause mortality.
Data Extraction: Two reviewers independently extracted data on study characteristics, Î²-blocker dosing and heart rate reduction, and death.
Data Synthesis: The mean left ventricular ejection fraction in the 23 Î²-blocker trials ranged from 0.17 to 0.36, and more than 95% of the 19Â 209 patients had systolic dysfunction. The overall risk ratio for death was 0.76 (95% CI, 0.68 to 0.84); however, heterogeneity testing revealed moderate heterogeneity among trials (I2Â = 30%), which was associated with the magnitude of heart rate reduction achieved within each trial (P for meta-regressionÂ = 0.006). For every heart rate reduction of 5 beats/min with Î²-blocker treatment, a commensurate 18% reduction (CI, 6% to 29%) in the risk for death occurred. No significant relationship between all-cause mortality and Î²-blocker dosing was observed (risk ratio for death, 0.74 [CI, 0.64 to 0.86]) in high-dose Î²-blocker trials vs. 0.78 [CI, 0.63 to 0.96] in low-dose Î²-blocker trials; P for meta-regressionÂ = 0.69).
Limitations: The analysis is based on aggregate data and resting heart rates. Few patients in these trials had bradycardia or diastolic dysfunction at baseline.
Conclusion: The magnitude of heart rate reduction is statistically significantly associated with the survival benefit of Î²-blockers in heart failure, whereas the dose of Î²-blocker is not.