Catheter ablation of atrial fibrillation with box isolation of fibrotic areas: Lessons on fibrosis distribution and extent, clinical characteristics, and their impact on long‐term outcome

Introduction The BIFA concept (box isolation of fibrotic areas) supplementing pulmonary vein isolation (PVI) was implemented in atrial fibrillation (AF) patients with fibrotic atrial cardiomyopathy (FACM) to improve catheter ablation outcomes. Methods and results Ninety‐two patients with FACM underwent PVI + BIFA. We investigated patient characteristics (58 persistent/34 paroxysmal, 68 ± 8 years, LA 44 ± 7 mm, CHA2DS2‐VASc 2.6 ± 1.3, FACM I: 15.2%, II: 53.3%, III: 26.1%, IV: 5.4%), periprocedural data concerning fibrosis extent/distribution, and their impact on outcome. Based on severe fibrosis areas (SFAs) of 13.5 ± 13.9 cm2 detected by voltage mapping, 1.4 ± 0.5 boxes (n = 1–3, 2.2–35.3 cm2) were applied in the left atrium. With higher grade FACM, SFAs increased and maximum voltage decreased (I/IV: 6.29/3.18 mV). Anterior (ant.) SFAs were found to be more common and larger than posterior (post.) SFAs (58.3% vs. 42.6%, ant. 8.0 ± 8.0 vs. post. 4.7 ± 6.8 cm2). In 40 of 92 (43%) patients, both atrial walls were affected with rare cases of solely post. fibrosis (6 of 92, 6.6%). Women (39 of 92, 42%) showed FACM III+IV more often than men (P = 0.022) and can still present paroxysmal while persistent males are more likely to have FACM I‐II. Single and multiple procedure (1.2/patient) success was 69% and 83% after 16 ± 8 months with an unfavorable impact of large SFA size, both‐sided fibrosis and reduced maximum voltage, independently of patient characteristics and AF type. Conclusion FACM patients are a challenging AF subgroup for catheter ablation. Women seem to show FACM III+IV more often than men. The distribution of left atrial fibrosis is variable but more pronounced anteriorly. Atrial disease is characterized by SFA size but also maximum voltage reduction, both with implications on ablation outcome. Using BIFA, success rates of patients without fibrosis can be approached but are limited in FACM III+IV.