Heart rate and outcome in heart failure with reduced ejection fraction: Differences between atrial fibrillation and sinus rhythm-A CIBIS II analysis

Background: Heart rate has been associated with prognosis in patients with heart failure with reduced ejection fraction (HFREF) and sinus rhythm; whether this also holds true in patients with atrial fibrillation (AF) is unknown.

Hypothesis: To evaluate cardiac rhythm and baseline heart rate and the influence of outcome in patients with HFREF enrolled in the Cardiac Insufficiency Bisoprolol Study II.

Methods: In total, 2539 patients were stratified according to their baseline heart rhythm (AF or sinus rhythm) and into quartiles of heart rate ( 90 bpm). The primary outcome was all-cause mortality. Mean follow-up was 1.3 years.

Results: Mean age was 61 years, mean left ventricular ejection fraction was 28%, and 80% were male. A total of 521 (21%) patients had AF at baseline. The risk associated with all-cause mortality for each 5 bpm increase in heart rate in patients with sinus rhythm (hazard ratio [HR]: 1.06, 95% confidence interval [CI]: 1.01-1.11, P = 0.012) was significantly different from those with AF (HR: 1.00, 95% CI: 0.94-1.07, P = 0.90, P for interaction = 0.041). The risk associated with higher heart rate in sinus rhythm was primarily attributable to excess risk in the highest quartile (HR: 1.64, 95% CI: 1.18-2.30, P = 0.003). Allocation to bisoprolol did not modify the interaction between heart rate, rhythm and outcome.

Conclusions: In HFREF patients with AF, a higher heart rate is not associated with increased event rates in contrast to HFREF patients with sinus rhythm.