Arrhythmia may confound heart failure treatment
medwireNews: Meta-analysis findings question whether beta-blocker treatment remains effective in patients who have heart failure (HF) with reduced left ventricular ejection fraction (LVEF) if they also have atrial fibrillation (AF).
Beta-blocker treatment did not significantly reduce mortality among patients with AF, contrasting with the beneficial effect seen among those in sinus rhythm, report Dirk Van Veldhuisen (University Medical Center Groningen, the Netherlands) and team in the Journal of the American College of Cardiology: Heart Failure.
The meta-analysis covered four randomized controlled trials, involving four different beta blockers and 8680 patients with HF, 1677 (19%) of whom also had AF. The researchers caution that their analysis involved a subgroup that was not prespecified and assumed a class effect, ie, that the four beta blockers studied would have very similar effects.
Editorialists Michael Bristow and Ryan Aleong, from the University of Colorado in Aurora, USA, agree that the study is hypothesis generating and prospective studies are therefore needed.
"In that regard, it would appear to be ethical to compare placebo to a β-blocker in AF-HFREF [HF with reduced LVEF] patients in that available data support equipoise," they say.
Overall, patients in sinus rhythm had a significant 37% reduction in mortality risk when given a beta blocker versus a placebo, whereas AF patients had a nonsignificant 14% reduction.
Although there was a high proportion of AF patients in the four trials and they had 145 endpoint events between them, the researchers say that the study may still have been slightly underpowered for a survival analysis. If the treatment benefits were reduced, rather than completely abolished, in AF patients, then they may have lacked the statistical power to detect it.
However, they did find a significant interaction between AF status and treatment effect, supporting a reduced or absent effect in AF patients.
Bristow and Aleong note that beta blockers are not the first drugs for HF to prove less effective if patients also have AF. In the reverse scenario, some rate and rhythm control treatments for AF have adverse effects in HF patients.
"The clinician is thus faced with a relative lack of therapeutic options in the AF-HFREF patient," they say. "Based on the relatively high prevalence of AF and evidence that it worsens mortality rate in HF patients, treatment of AF-HFREF is a major unmet need in cardiovascular therapies."
medwireNews (www.medwirenews.com) is an independent clinical news service provided by Springer Healthcare Limited. © Springer Healthcare Ltd; 2013
By Eleanor McDermid, Senior medwireNews Reporter