Arai S, Kawamura M, Gokan T, et al. - Since it is likely that subclinical‐atrial fibrillation (AF) go untreated in the routine care of patients with cardiac resynchronization therapy defibrillator (CRT‐D), therefore, researchers investigated whether subclinical‐AF is related to heart failure (HF) hospitalization and increasing an inappropriate therapy. Participants were 153 patients exhibiting an ejection fraction less than 35%. Three groups were defined: subclinical‐AF (n = 30), clinical‐AF (n = 45) and no‐AF (n = 78). Participants were observed for 50 months following classification of the groups. According to the findings, a significantly increased risk of HF hospitalization was observed in relation to subclinical‐AF after CRT‐D implantation. Experts inferred that the risk of HF hospitalization might be impacted by the loss of the biventricular pacing and increasing an inappropriate therapy.