Four-year efficacy of cardiac resynchronization therapy on exercise tolerance and disease progression: the importance of performing atrioventricular junction ablation in patients with atrial fibrillation.

Objectives: The goal of this study was to investigate the effects of cardiac resynchronization therapy (CRT) in heart failure patients with permanent atrial fibrillation (AF) and the role of atrioventricular junction (AVJ) ablation.
Background: Cardiac resynchronization therapy has been proven effective in heart failure patients with sinus rhythm (SR). However, little is known about the effects of CRT in heart failure patients with permanent AF.
Methods: Efficacy of CRT on ventricular function, exercise performance, and reversal of maladaptive remodeling process was prospectively compared in 48 patients with permanent AF in whom ventricular rate was controlled by drugs, thus resulting in apparently adequate delivery of biventricular pacing (>85% of pacing time), and in 114 permanent AF patients, who had undergone AVJ ablation (100% of resynchronization therapy delivery). The clinical and echocardiographic long-term outcomes of both groups were compared with those of 511 SR patients treated with CRT.
Results: Both SR and AF groups showed significant and sustained improvements of all assessed parameters (model p < 0.001 for all parameters). However, within the AF group, only patients who underwent ablation showed a significant increase of ejection fraction (p < 0.001), reverse remodeling effect (p < 0.001), and improved exercise tolerance (p < 0.001); no improvements were observed in AF patients who did not undergo ablation.
Conclusions: Heart failure patients with ventricular conduction disturbance and permanent AF treated with CRT showed large and sustained long-term (up to 4 year) improvements of left ventricular function and functional capacity, similar to patients in SR, only if AVJ ablation was performed.