Newly detected atrial fibrillation in patients with an implantable cardioverter-defibrillator is a strong risk marker of increased mortality

BackgroundAtrial fibrillation (AF) has been associated with higher rates of all-cause mortality in patients with heart failure (HF). The risk of newly detected AF in patients receiving implantable cardioverter-defibrillator (ICD) therapy is unknown.MethodsNewly detected AF was evaluated in all patients enrolled in the Inhibition of Unnecessary RV Pacing with AV Search Hysteresis in ICDs (INTRINSIC RV) study. The relationships between AF and endpoints (total mortality, ICD shocks, and HF hospitalizations) were analyzed retrospectively with proportional-hazards models.ResultsAt 108 centers, 1530 patients meeting VITALITY AVT ICD indications were followed for 12 months. Of these, 1356 (89%) had no history of AF at the time of implant. Patients with a history of AF had a higher prevalence of HF (52% vs. 36%; P <.01) and had higher rates of HF hospitalization (hazard ratio [HR] 2.14 [1.29–3.54], P <.01), death (HR 2.22 [1.26–3.92], P <.01), and any ICD shock (HR 1.75 [1.19–2.58], P <.01) compared with those with no history. AF incidence during the first 3 months of implant was available in 1317 (86%; 1170 no AF, 147 history of AF) patients. New-onset AF during the first 3 months of implant (45 of 1170, 4%) was associated with a significant increased risk of death (HR 2.86 [1.02–8.05], P = .05) but not with inappropriate ICD shock (HR 2.43 [0.87–6.75], P = .09) or HF hospitalization (HR 1.17 [0.28–4.82], P = .83).ConclusionHistory of AF at the time of ICD implant identifies additional risk of HF and death. Newly detected AF is associated with significantly higher rates of death. The relationship between newly detected AF and inappropriate ICD shock or HF hospitalization is uncertain and requires further study.