BackgroundCongestive heart failure patients with reduced left ventricular ejection fraction (HFrEF) and sleep-disordered breathing (SDB) are at an increased risk of nocturnal cardiac arrhythmias. SDB can be effectively treated with adaptive servo-ventilation (ASV). Therefore, we tested the hypothesis that ASV therapy reduces nocturnal arrhythmias and heart rate in patients with HFrEF and SDB.