The interaction between atrial fibrillation and mitral regurgitation: Insights from the CABANA randomized clinical trial

Abstract Aims Atrial fibrillation (AF) and mitral regurgitation (MR) frequently coexist. While catheter ablation is a key rhythm‐control strategy in AF, its impact on MR severity remains uncertain. This study evaluates the effects of catheter ablation on AF recurrence, functional status, and MR progression in patients with AF and baseline MR. Methods and results This sub‐analysis included 1423 patients (65% of the overall CABANA cohort) with available baseline echocardiography. Participants were randomized to catheter ablation or pharmacological therapy. The primary endpoint was the composite of all‐cause mortality and cardiovascular hospitalization. Secondary endpoints included AF recurrence, changes in MR severity, and functional status. At baseline, 722 patients (52%) had MR, including 582 with mild and 140 with ≥moderate MR, with characteristics suggestive of an atrial functional mechanism. Catheter ablation significantly reduced AF recurrence compared to pharmacological therapy (odds ratio [OR] 0.56, 95% confidence interval [CI] 0.50–0.62, p < 0.001). The presence or absence of MR did not interact with randomization in terms of its neutral effect on all‐cause mortality and cardiovascular hospitalization ( p for interaction = 0.115). Baseline MR increased the risk of AF recurrence (OR 1.46, 95% CI 1.40–1.74, p < 0.001). However, the benefit of ablation on functional status was greater in patients with MR compared to those without ( p for interaction < 0.001). Follow‐up echocardiography ( n = 248) showed a greater reduction in MR severity in the ablation group versus drug therapy ( p for interaction = 0.040). Conclusion Catheter ablation was superior to pharmacological therapy in rhythm control and may reduce MR severity over time. These findings highlight ablation's potential structural and symptomatic benefits, pending specifically designed clinical trials.