Atrial Substrate Progression in AF Patients: Insights From Unipolar Mapping

Atrial substrate progression is common among patients with atrial fibrillation (AF). Unipolar voltage mapping more comprehensively characterizes the atrial substrate compared with bipolar mapping.

This study aimed to characterize atrial substrate progression in patients with recurrent AF using unipolar mapping after pulmonary vein isolation.

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.

A total of 50 patients (mean age 59.5 ± 12.6 years; 40 males) were enrolled. Compared with index ablation, redo ablation demonstrated significantly larger bipolar LVZ (Bi-LVZ) total area (21.25 vs. 15.86 cm², 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).

Uni-LVZ characterizes the atrial substrate progression, with the higher Uni/Bi ratio during index ablation indicates greater Bi-LVZ expansion at redo ablation.