Eggington, Simon

Introduction: Atrial Fibrillation (AF) is an important contributor to insufficient left ventricular pacing and mortality in patients undergoing cardiac resynchronization therapy (CRT). The incidence and prevalence of AF post-CRT implant, in patients with and without previous history of AF, has not previously been described. Hypothesis: AF prevalence in CRT patients, despite history of AF, is higher than previously understood. Methods: Subjects implanted with a CRT-Defibrillator (CRT-D) enrolled in the PainFree SST study and with device data collection were analyzed. Subjects who exited within 30 days of implant, had < 27 days of available daily AT/AF burden data, or had ≥ 10% of daily AT/AF data missing were excluded. We defined incidence and prevalence of clinically meaningful device documented AF using previously published criteria (≥1 day with AF > 6 hours). History of AF at enrollment was documented based on clinical history. Results: The analysis included 944 patients (68±11 years; 78% male, EF 28±9%, QRS 152±29 ms; 59% NYHA III/IV). The duration from implant to study exit or death was 2.0 ± 0.8 years (IQR 1.5-2.5). History of AT/AF was documented in 37% of patients at baseline. Overall, any AT/AF was found in 85.2 % of subjects during follow-up. Clinically meaningful AT/AF was found in 30.3% of subjects. Of the 345 subjects with history of AF at baseline, 51.9% had clinically meaningful AT/AF during follow-up vs.17.9% for subjects without known AF (p<0.0001). 24.8% of subjects experienced at least one day of ≥ 23h of AT/AF. 6.9% of subjects had ≥ 23h of AT/AF for > 95% of days with data. Conclusions: AF occurs in a substantial proportion of CRT-D patients and clinically documented history of AF prior to CRT-D implant corresponds poorly with device documented AT/AF during follow-up. Device documented AF should be evaluated in CRT-D patients with and without previous history of AF to individualize strategies to maximize left ventricular pacing and minimize disruption due to AF.