Epicardial adipose tissue in paroxysmal and persistent atrial fibrillation ablation using photon counting CT and automated 3D atrial segmentation: The Prospective AFAT Study.

BACKGROUND: Epicardial adipose tissue (EAT) may contribute to atrial fibrillation (AF) pathogenesis and recurrence after catheter ablation, but data using precise volumetric quantification alongside systematic body composition assessment are limited. OBJECTIVE: To quantify biatrial EAT using photon-counting CT (PCCT) with semiautomated 3D segmentation and assess its association with arrhythmia recurrence after first-time catheter ablation in paroxysmal and persistent AF. METHODS: In this prospective observational study, 210 adults undergoing first-time catheter ablation at the German Heart Centre Munich underwent preprocedural PCCT with 3D biatrial EAT reconstruction and protocolized whole-body composition assessment. The primary endpoint was freedom from any atrial arrhythmia at one year following an 8-week blanking period, assessed by 7-day Holter monitoring at 3, 6 and 12 months. RESULTS: Median age was 68.0 years and median body mass index 27.0 kg/m2 (IQR 24.5-30.0). Median left atrial (LA) EAT volume was 30.4 mL (IQR 23.5-40.1) and right atrial EAT 31.2 mL (IQR 23.8-38.0); the two were strongly correlated (r = 0.92, P < 0.0001). Patients with persistent AF had higher LA and right atrial EAT than those with paroxysmal AF (32.1 vs 28.0 mL and 33.4 vs 27.7 mL; P < 0.01). One-year arrhythmia freedom was 81.9% in paroxysmal and 57.3% in persistent AF (P = 0.005). In multivariable Cox regression, greater LA EAT per 10-mL increase was associated with recurrence in persistent AF (HR 1.51, 95% CI 1.06-2.15) but not paroxysmal AF (HR 0.79, 95% CI 0.54-1.15; P for interaction = 0.014). LA EAT was not associated with low-voltage substrate. CONCLUSION: PCCT enables precise biatrial EAT quantification. LA EAT was associated with arrhythmia recurrence in persistent but not paroxysmal AF, supporting its potential as an imaging biomarker.