Effect of Beta-Blocker Treatment on V O2peak in Patients With HF
What is the effect of prolonged beta-blocker treatment on peak oxygen consumption (V˙O2peak) in patients with chronic heart failure (HF)?
A systematic search was conducted of relevant databases (inception to March 2017) for randomized controlled trials that assessed beta-blocker treatment effects on V˙O2peak in patients with chronic HF. Meta-analysis was performed to determine standardized mean difference between the effects of beta-blocker compared with placebo treatment on V˙O2peak. Two secondary outcomes, peak exercise performance and New York Heart Association (NYHA) functional class, and potential moderating factors were analyzed using sub-group analysis comparing studies grouped by qualitative variable (agent/type of beta-blocker treatment and methodology of exercise testing).
Fourteen randomized controlled trials met the inclusion criteria and amounted to 616 patients with chronic HF, 324 of whom were allotted to beta-blocker and 292 to placebo. The V˙O2peak range was 13.5-22 mL/kg/min, and the NYHA functional class range was 1.6-2.8. Eight studies used beta-1-selective beta-blocker, and 6 used non-selective beta-blocker, for a range of 3-24 months. Regardless of beta-blocker treatment characteristics, type, or exercise testing modality, beta-blocker had no effect on V˙O2peak compared with placebo. Meta-regression analyses revealed no influence of potential moderating quantitative variables. In beta-blocker treatment compared with placebo, peak exercise performance (11 studies, n = 493) did not differ, and NYHA functional class (7 studies, n = 347) was improved. No heterogeneity was detected among studies.
The blunting of peak heart rate is a well-documented mechanism that attenuates the adrenergic over-activation that characterizes HF. However, this meta-analysis demonstrates that prolonged beta-blocker treatment in chronic HF does not affect V˙O2peak, a consistent finding across a variety of beta-blocker intervention characteristics. Additionally, peak exercise performance is preserved and NYHA functional class is improved in patients with beta-blocker treatment in chronic HF.
Prolonged life and reduced hospitalizations are valuable primary endpoints of beta-blocker treatment in chronic HF. Considering the poor prognosis for HF, functional benefits, such as preserved exercise capacity and improved functional class, offer important quality-of-life benefits as well.
Keywords: Oxygen Consumption, Heart Failure, Adrenergic beta-Antagonists, Exercise Test, Heart Rate, Quality of Life
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