Son MK, Park JJ, Lim NK, et al. - Researchers investigated the prognostic worth of atrial fibrillation (AF) in patients experiencing heart failure (HF) and preserved, mid-range or reduced ejection fraction (EF). In a prospective, observational, multicentre cohort study, the Korean Acute Heart Failure registry, patients hospitalised for acute HF were recruited between March 2011 and February 2014. The types of HF included reduced EF [HFrEF, left ventricular EF (LVEF) < 40%], mid-range EF (HFmrEF, LVEF 40%–49%) or preserved EF (HFpEF, LVEF ≥ 50%). Findings revealed a more common prevalence of AF with increasing EF. Only patients with HFpEF demonstrated a link between AF and increased mortality. A link of AF with an increased risk of stroke was identified in patients with HFrEF or HFpEF.