Substrate Unmasking via High‐Density Omnipolar Mapping Under Rapid Pacing in Atrial Fibrillation

Background Substrate mapping for atrial fibrillation (AF) ablation commonly relies on sinus rhythm (SR) maps, which may overlook rate‐dependent electrophysiological changes. Objective This study aimed to evaluate the diagnostic and prognostic value of rate‐dependent substrate characterization using high‐density omnipolar mapping under rapid pacing. Methods In a prospective cohort of 46 patients (5 controls, 22 paroxysmal AF [PAF], 19 persistent AF [PeAF]), bi‐atrial conduction velocity (CV) and low‐voltage zones (LVZ) were assessed across seven mapping conditions: SR and graded pacing (600, 400, 300 ms) from the distal coronary sinus (CSD) and high right atrium (HRA). Results CV decreased with faster pacing across all cohorts. At 300 ms, PeAF patients exhibited significantly slower CV than PAF and controls (0.60 ± 0.07 vs. 0.72 ± 0.06 vs. 0.90 ± 0.05 m/s; p < 0.001). The global LVZ burden was greater in PeAF than PAF at 300 ms (58.71 [39.84–68.69] vs. 26.18 [20.94–37.40]; p = 0.009). Decremental pacing was associated with progressive bi‐atrial conduction slowing in AF, most pronounced in PeAF (0.76 ± 0.08 vs. 0.74 ± 0.06 vs. 0.69 ± 0.02 vs. 0.60 ± 0.07 m/s; p < 0.001). Rapid pacing at 300 ms showed the numerically highest discriminative capacity. Patients with global CV < 0.67 m/s (AUC 0.749; p = 0.019) or LVZ% > 43.4% (AUC 0.681; p = 0.008) at 300 ms were associated with a higher risk of recurrence. Conclusion Rapid pacing at 300 ms reveals latent bi‐atrial substrate occult during SR and may improve risk stratification.