Risk of Atrial Fibrillation Recurrence After Modified Cox-Maze IV Surgery: Comparing Atrial Functional Mitral Regurgitation and Rheumatic Mitral Regurgitation

Background: The comparative efficacy of the modified Cox-Maze IV procedure (CMP IV) in treating atrial fibrillation (AF) in patients with atrial functional mitral regurgitation (AFMR) and those with rheumatic mitral regurgitation (RMR) remains inadequately characterized. Therefore, this study aimed to evaluate and compare postoperative AF recurrence rates and clinical outcomes between these two etiologically distinct groups. Methods: A retrospective analysis was conducted on 221 patients (AFMR group: n = 53; RMR group: n = 168) with concomitant long-standing persistent AF who underwent mitral valve surgery combined with modified CMP IV or other concomitant procedures at our institution between January 2019 and September 2024. To address baseline imbalances, propensity score matching was performed at a 1:1 ratio, resulting in well-matched cohorts of 32 patients with AFMR and 32 with RMR patients for the final analysis. The primary endpoint was AF recurrence. Statistical comparisons utilized chi-square tests, t-tests, exact McNemar tests, and paired t-tests. Results: After PSM, 32 patients remained in each group with balanced baselines. The AFMR group showed a higher trend toward postoperative AF recurrence. Pre‑discharge AF recurrence rates did not differ significantly between groups (37.5% vs. 12.5%; p = 0.057), however, the risk of AF recurrence before discharge was significantly higher in the AFMR group (OR = 3.67, 95% CI: 1.02–13.14, p = 0.046). At the 1-year follow-up, a statistically significant difference in AF recurrence was observed between the two groups (31.2% vs 6.2%, p = 0.021), and the risk difference persisted (OR = 9.00, 95% CI: 1.14–71.04, p = 0.037). Kaplan–Meier analysis showed a significant difference in freedom from AF recurrence (log‑rank χ2 = 6.33; p = 0.012), supported by sensitivity analyses (log‑rank χ2 = 6.01; p = 0.014). Mortality did not differ at 30 days (3.1% vs. 0%; p = 1.000) or 1 year (3.1% vs. 3.1%; p = 1.000), with comparable overall survival (log‑rank p = 0.99). Conclusions: In patients undergoing mitral valve surgery with modified CMP IV, those with AFMR exhibit a significantly higher risk of postoperative AF recurrence compared with patients with RMR, despite similar early-term survival outcomes. Postoperative AF monitoring should be intensified in patients with AFMR to improve long-term outcomes.