Left atrial intramyocardial fat at pulmonary vein reconnection sites during atrial fibrillation redo ablation

AIMS: Electrical reconnections between pulmonary veins (PVs) and the left atrium (LA) are frequently responsible for atrial fibrillation (AF) recurrences after pulmonary vein isolation (PVI). Multidetector computed tomography (MDCT)-derived images can be post-processed to detect intramyocardial fat (inFAT) by signal radiodensity thresholding. The role of inFAT on PV-LA reconnections remains unknown. The aim of this study was to analyse the relationship between inFAT localization at pre-procedural MDCT-derived inFAT maps from first AF ablation and PV-LA reconnections in patients with AF recurrence undergoing redo ablation. METHODS AND RESULTS: We included 45 consecutive patients who underwent AF redo ablation presenting at least one PV-LA reconnection. First AF ablation pre-procedural MDCT-derived data were post-processed with ADAS 3D™ to create 3D LA inFAT maps, which were loaded into CARTO3 navigation system and merged with the electroanatomical map for reconnection site analysis. In 103 out of 156 (66.0%), PV-LA reconnection points inFAT was identified in the 6 mm diameter tag point depicted in the navigation system. When dividing the PVI line into standardized segments, those identified as containing PV-LA reconnection points (i.e. reconnection segments) exhibited significantly higher total inFAT volumes compared with non-reconnection segments (8.05 ± 6.56 vs. 5.40 ± 5.18 μL, P < 0.001). Additionally, reconnection segments showed greater volumes of inFAT components, specifically dense inFAT (0.06 ± 0.06 vs. 0.03 ± 0.04 μL, P < 0.001) and fat-myocardial admixture (7.98 ± 6.52 vs. 5.37 ± 5.16 μL, P < 0.001). CONCLUSION: Intramyocardial fat is co-localized with two-thirds of PV-LA reconnection points in patients undergoing AF redo ablation. Reconnection segments exhibit significantly higher inFAT volumes compared to non-reconnection segments. This proof-of-concept study suggests that inFAT may play a role in PV-LA electrical reconnections following PVI.