Impact of atrial fibrillation/flutter on outcomes of patients with implantable cardioverter defibrillators: A sub-analysis of the Nippon Storm study

Background: Implantable cardioverter-defibrillator and cardiac resynchronization therapy using a defibrillator (ICD/CRT-D) are established means of reducing mortality due to ventricular arrhythmia. Although atrial fibrillation/flutter (AF) is the most common cardiac arrhythmia in patients with heart disease, the impact of AF on the prognosis of patients with ICD/CRT-D remains controversial. Methods and Results: We analyzed data from the Nippon Storm Study, a prospective observational study of 1570 patients that was conducted at 48 Japanese ICD centers. We allocated 1549 participants to AF and non-AF groups, compared their clinical data at the time of enrollment, and monitored the incidences of mortality, hospitalization, and appropriate and inappropriate ICD/CRT-D therapy during a median 28 months. When the AF (n = 257, 16.6%) and non-AF-(n = 1292, 83.4%) groups were compared, the AF group was older (67.7 vs. 61.4 years; p<0.0001), and had lower left ventricular ejection fraction (38.0 ± 17.0% vs. 43.5 ± 18.9%; p<0.0001). During follow up, mortality was significantly higher in the AF than the non-AF group (p<0.0001). In multivariate analysis, AF was significantly associated with all-cause mortality [p = 0.013; hazard ratio (HR)=1.62]. Inappropriate ICD/CRT-D therapy occurred in 40/257 patients (15.6%) and AF was associated with a higher prevalence of inappropriate ICD/CRT-D therapy (p<0.0001; HR=2.25). Conclusion: The presence of AF at ICD/CRT-D implantation carries subsequent independent risks of 1.62-fold for death and 2.25-fold for inappropriate therapy.