A novel algorithm increases the delivery of effective cardiac resynchronization therapy during atrial fibrillation: The CRTee randomized crossover trial

BACKGROUND Cardiac resynchronization therapy (CRT) requires a high percentage of ventricular pacing (%Vp) to maximize its clinical benefits. Atrial fibrillation (AF) has been shown to reduce %Vp in CRT due to competition with irregular intrinsic atrioventricular (AV) conduction. We report the results of a prospective randomized crossover trial evaluating the amount of effective CRT delivered during AF with a novel algorithm (eCRTAF). OBJECTIVE The purpose of this study was to determine whether eCRTAF increases the amount of effective CRT delivered during AF compared to a currently available rate regularization algorithm. METHODS Patients previously implanted with a cardiac resynchronization therapy-defibrillator and with a history of AF and intact AV conduction received up to 4 weeks of control (Conducted AF Response) and up to 4 weeks of eCRTAF in a randomized sequence. The percent effective CRT (%eCRT) pacing, which excludes beats without left ventricular capture, %Vp, and mean heart rate (HR) were recorded during AF and sinus rhythm. RESULTS The eCRTAF algorithm resulted in a significantly higher % eCRT during AF than control (87.8% +/- 7.8% vs 80.8% +/- 14.3%; P < .001) and % Vp during AF than control (90.0% +/- 5.9% vs 83.2% +/- 11.9%; P< .001), with a small but statistically significant increase in mean HR of 2.5 bpm (79.5 +/- 9.7 bpm vs 77.0 +/- 9.9 bpm; P < .001). CONCLUSION In a cohort of CRT patients with a history of AF, eCRTAF significantly increased % eCRT pacing and %Vp during AF with a small increase in mean HR. This algorithm may represent a novel noninvasive method of significantly increasing effective CRT delivery during AF, potentially improving CRT response.