Background: Posterior wall isolation (PWI) combined with pulmonary vein isolation (PVI) has been proven effective for persistent atrial fibrillation (AF). Intra-box ablation, defined as application in the “box” area during PWI in this study, is sometimes necessary when linear ablation of the roof and bottom fails to achieve complete isolation. This study aimed to investigate the factors of patients requiring intra-box ablation and to evaluate the effect of intra-box ablation on clinical outcomes.
Methods: This is an observational study including patients who underwent PVI and PWI for persistent AF in the first procedure from June 2017 and March 2020, at the Tokyo Metropolitan Hiroo Hospital. When linear ablation of the roof and bottom failed to complete PWI, intra-box ablation was added. Six months after the procedure, patients undertook follow-up electrophysiological study and additional ablation as the second procedure. Findings of the left atrium (LA) mapping and ablation in the first procedure and posterior wall (PW) reconnection in the second procedure were evaluated. Patient characteristics and outcomes were compared between patients with and without intra-box ablation.
Results: Of the 93 patients included in this study, successful PWI was achieved in 91 (mean age, 67.5±9.8 years; male, 75.3%), and intra-box ablation was needed in 59 (63.4%). Shorter PW activation time (40.3±10.4 vs 51.3±15.2, p=0.026) and larger upward conduction patterns in the PW were significant association with the necessity of intra-box ablation. More PW reconnection in the second procedure was observed in patients with intra-box ablation than in those without intra-box ablation (21/28,75.0% vs 8/20, 40.0%; p=0.020).
Conclusion: We showed that the requirement of intra-box ablation was related to lower durability of PW. Findings of LA mapping suggested the possibility that PW conduction velocity and patterns was one of the mechanisms of failure of linear PWI.
Credits: Sayuri Tokioka; Seiji Fukamizu; Takashi Kimura; Masao Takahashi; Takeshi Kitamura; Rintaro Hojo