Electrical Remodeling and Low Voltage Areas in Atrial Fibrillation Patients with Functional Mitral Regurgitation: A Multicenter Evaluation

Background: Atrial fibrosis may act as a substrate for atrial fibrillation (AF) and atrial functional mitral regurgitation (MR); thus, recognition is required to select the optimal therapeutic intervention. Methods: We examined clinical data from 1045 consecutive patients in three centers who underwent catheter ablation for persistent AF between 2020 and 2022. 75 patients met the moderate and severe MR criteria and completed a 1-year follow-up. Voltage mapping during the ablation procedure was reviewed to classify the extent of atrial fibrosis. Results: Significant atrial fibrosis was found in 34 patients (45.3%), and these patients had a higher prevalence of congestive heart failure (New York Heart Association (NYHA) II–III: 76.5% vs. 36.6%, p < 0.001) and an increased incidence of biatrial enlargement at baseline than the mild fibrosis group. At the 1-year post-ablation period, the entire cohort exhibited a decrease in left atrial size (41.6 ± 6.5 mm vs. 45.5 ± 5.3 mm, p < 0.001), and a significant reduction in MR was achieved in 70.7% of patients. The significant fibrosis group had a higher recurrence rate of atrial arrhythmias (55.9% vs. 22.0%, log-rank p = 0.002) and no significant change in atria size compared with baseline diameters (left atrium, 44.4 ± 6.4 mm vs. 47.2 ± 5.6 mm, p = 0.068; right atrium, 44.7 ± 11.2 mm vs. 46.7 ± 6.2 mm, p = 0.427). Conclusions: This study revealed a considerable proportion of significant fibrosis in patients with atrial functional MR and AF, leading to limited effectiveness in reducing atrial size following catheter ablation. Optimal intervention to reduce atrial size and recurrent arrhythmias in this population requires further investigation.