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Afib May Not Up Death Risk in Heart Failure

By Todd Neale, Senior Staff Writer, MedPage Today
Published: August 02, 2011
Reviewed by Robert Jasmer, MD; Associate Clinical Professor of Medicine, University of California, San Francisco and Dorothy Caputo

Action Points
Explain that atrial fibrillation may not be an independent risk factor for death in patients optimally treated for heart failure, a finding that is in contrast to prior studies.

Point out that there was a high rate of adherence to guideline-recommended medical therapy for heart failure in these patients, as evidenced by 88.4% of patients who received ACE inhibitors, angiotensin receptor blockers, or both, and 82.8% who used beta-blockers.
Atrial fibrillation may not be an independent risk factor for death in patients optimally treated for heart failure, a Norwegian study showed.

After adjustment for several confounders, having atrial fibrillation was not associated with a greater mortality risk in patients treated at specialized heart failure clinics (HR 1.03, 95% CI 0.90 to 1.19), according to Arnljot Tveit, MD, PhD, of Baerum Hospital in Rud, Norway, and colleagues.

The finding, however, contrasts with that of a 2009 meta-analysis, the researchers reported online in Clinical Cardiology.

Half of the 12 studies included in the meta-analysis from Mamas et al. did not demonstrate that atrial fibrillation was an independent risk factor for death (Eur J Heart Fail 2009; 11: 676–683).

Tveit and colleagues noted, too, that the percentage of patients taking guideline-recommended medical therapy for heart failure was higher in the current study than in the studies included in the meta-analysis.

"This improved medical treatment of heart failure and optimized thromboprophylaxis in atrial fibrillation may have reduced the impact of atrial fibrillation on prognosis in heart failure patients," they wrote.

Although several previous studies -- including observational studies and subset analyses of randomized trials -- have shown that atrial fibrillation is associated with a greater mortality risk in patients with heart failure, a few have shown that the relationship disappears after controlling for other risk factors.

To further explore the issue, Tveit and colleagues analyzed data from patients referred to 24 Norwegian specialized heart failure clinics -- which focused on optimization of treatment and patient education -- from October 2000 to February 2008. Mortality information came from the national statistics bureau.

The analysis included 4,048 patients with heart failure; about one-third (34.4%) had atrial fibrillation.

Overall, adherence to guideline-recommended medical therapy was high -- 88.4% of patients received ACE inhibitors, angiotensin receptor blockers, or both, and 82.8% used beta-blockers. Of the patients with atrial fibrillation, 85.9% were on warfarin.

Without adjusting for any confounders, there was a higher risk of death through a median follow-up of 28 months among patients with atrial fibrillation than among those in sinus rhythm (HR 1.18, 95% CI 1.04 to 1.33, P=0.008).

However, after adjustment for confounders -- including age, heart failure severity, coronary artery disease as the main cause of heart failure, use of any loop diuretic, hemoglobin level, and serum creatinine -- the relationship was no longer significant (HR 1.03, 95% CI 0.90 to 1.19, P=0.619). Age was the strongest confounder and adjusting for that factor alone rendered the association nonsignificant.

Researchers suggested that the higher mean age of those with atrial fibrillation in this study (74 years) compared with other studies is more representative of the general atrial fibrillation population. On average, those with atrial fibrillation were six years older than those without Afib.

The findings nullifying atrial fibrillation as a predictor of death were similar in the subgroups of patients with ischemic heart disease as the main cause of heart failure and those with less severe heart failure (NYHA Class I/II).

The authors acknowledged some limitations of the analysis, including the lack of information on the rate of implantable cardioverter-defibrillator use, on use of anti-arrhythmic drugs and digoxin, and on the temporal pattern or duration of atrial fibrillation.

In addition, they wrote, the findings may not be applicable to patients treated outside of a specialized heart failure clinic.