High‐Density Spectral Analysis for Bi‐Atrial Arrhythmogenic Substrate During Non‐Paroxysmal Atrial Fibrillation

ABSTRACT Background Spectral analysis has been utilized to identify localized sites exhibiting high dominant frequency (DF) and high regularity—the critical arrhythmogenic substrate driving atrial fibrillation (AF). This study aimed to elucidate the spectral characteristics of focal activation (FoA) and rotational activation (RoA) sites during AF using a high‐density mapping system. Methods CARTOFINDER mapping was prospectively performed in both atria of 47 consecutive non‐paroxysmal AF patients using the Octaray catheter prior to ablation. Endocardial unipolar electrograms were exported offline for spectral analysis of DF and the regularity index (RI). Results CARTOFINDER assessed a total of 48 153 mapping points. Given substantial inter‐subject variability in mean DF, the difference between each point's DF and the subject‐level mean DF was defined as the dominant frequency deviation (DFD). The left atrium (LA) demonstrated significantly higher DFD and RI than the right atrium (both p < 0.001), with the LA roof recording the highest values across all segments. Both FoA and RoA sites exhibited significantly higher DFD and RI compared with sites without FoA and RoA (both p < 0.001). DFD and RI increased progressively with increasing FoA repetitions (both p < 0.001). In contrast, high‐repetition RoA sites (> 16 repetitions) showed a significantly higher RI (0.42 ± 0.13 vs. 0.36 ± 0.12, p < 0.001) but a paradoxically lower DFD (0.14 ± 0.64 Hz vs. 0.26 ± 0.74 Hz, p < 0.001) compared with low‐repetition RoA sites. Conclusions The combination of CARTOFINDER mapping and spectral analysis may contribute to the mechanistic understanding of non‐paroxysmal AF.