Left atrial geometry in atrial Fibrillation: A comparison between electroanatomical mapping and computed tomography

Atrial fibrillation (AF) involves heterogeneous remodelling of the left atrium (LA), making accurate geometric quantification clinically relevant. CT is the reference standard for anatomical assessment, whereas electroanatomical mapping (EAM) provides intraprocedural reconstruction with electrophysiological information. However, agreement between both modalities remains incompletely characterized.

We retrospectively analyzed 211 patients undergoing first-time catheter ablation with pre-procedural CT imaging. LA volume, surface area, and sphericity were derived from CT and EAM. A common ellipsoidal model was fitted to both datasets for comparison via semi-axes (a, b, c). Agreement was assessed using Pearson correlation and Bland-Altman analysis. Geometric differences were quantified using RMS radial differences and Dice similarity on both original meshes and ellipsoidal approximations.

EAM correlated with CT for volume (r = 0.58), area (r = 0.56), and sphericity (r = 0.49) (all p < 0.001). Bland-Altman analysis demonstrated systematic overestimation of volume (11.1 cm³, 13.2 %) and surface area (8.9 cm², 9.6 %), with slight underestimation of sphericity (-0.01). RMS radial differences were higher for original meshes than ellipsoidal approximations (0.14 vs 0.08), while Dice similarity was higher for ellipsoids than original geometries (0.89 IQR [0.85-0.91] vs 0.81 IQR [0.77-0.83]).

EAM provides a rapid intraprocedural approximation of left atrial geometry but does not fully reproduce CT-derived anatomy. While global shape is partially preserved, systematic scale differences and local discrepancies persist, supporting its role as a complementary rather than substitute modality.