Atrial posterior wall fibrosis >25% signals atrial fibrillation recurrence

Background Pulmonary vein isolation (PVI) is the cornerstone of ablation for atrial fibrillation (AF), but recurrence rates remain high. Left atrial (LA) fibrosis, a key factor in AF recurrence, is challenging to assess. Our prior study found that fibrosis>25% in the left atrial posterior wall, measured by 18F-AlF-FAPI PET/MR imaging, was linked to higher AF recurrence after PVI. We hypothesized that this 25% fibrosis threshold may help stratify patients who need treatment intervention beyond PVI. Methods In this prospective cohort study involving 66 patients with paroxysmal or persistent AF undergoing PVI, pre-procedural LA fibrosis was quantified by 18F-AlF-FAPI PET/MR imaging. Patients were categorized into two groups based on LA posterior wall fibrosis levels ≤25% vs. >25%. AF recurrence was evaluated over 12 months using 7-day continuous electrocardiographic monitoring. Results At 12 months, patients with >25% fibrosis experienced more AF recurrence than those with ≤25% (56.5% vs 7.0%, P<0.001). The AF recurrence difference remained apparent in patients with persistent AF (59.09% vs 10.53%, P=0.001). Multivariate analysis confirmed >25% fibrosis as an independent predictor of AF recurrence (OR 6.954–11.075, P<0.01) after adjusting for cardiac function and AF characteristics. ROC analysis showed fibrosis-based models had better discriminative ability (AUC: 85.38%, 95% CI: 76.31-94.44%) than models using only cardiac function and AF characteristics (AUC: 83.88%, 95% CI: 73.42-94.33). Conclusions LA posterior wall fibrosis >25%, detected by 18F-AlF-FAPI PET/MR, predicted higher AF recurrence risk within one-year post-PVI and may help identify patients who need additional treatment intervention beyond PVI.fibrosis severity and AF recurrencefibrosis extent in distinguishing AF rec