Atrial Substrate Progression in AF Patients: Insights From Unipolar Mapping

BACKGROUND: Atrial substrate progression is common among patients with atrial fibrillation (AF). Unipolar voltage mapping more comprehensively characterizes the atrial substrate compared with bipolar mapping. OBJECTIVE: This study aimed to characterize atrial substrate progression in patients with recurrent AF using unipolar mapping after pulmonary vein isolation. METHODS: In this single-center retrospective study, consecutive AF patients undergoing index and redo ablations were enrolled. Electroanatomic maps from both ablations were compared and assessed by unipolar and bipolar voltage. Low-voltage zone (LVZ) was defined as bipolar voltage <0.5 mV or unipolar voltage <1.6 mV. Patients were categorized into progression (n = 35) and nonprogression (n = 15) groups. RESULTS: , p = 0.007) and LVZ burden (0.20 vs. 0.14, p = 0.002). The progression group showed a higher LVZ burden (unipolar: 0.27 vs. 0.12, p = 0.007; bipolar: 0.16 vs. 0.09, p = 0.019) and a greater ratio of total unipolar to bipolar LVZ area (Uni/Bi) (1.75 vs. 1.34, p = 0.042) during index ablation compared with the nonprogression group. Linear regression revealed a positive correlation between index-ablation Uni/Bi ratio and the degree of Bi-LVZ area expansion at redo ablation (β = 7.20, p < 0.001). CONCLUSION: Uni-LVZ characterizes the atrial substrate progression, with the higher Uni/Bi ratio during index ablation indicates greater Bi-LVZ expansion at redo ablation.