Periatrial Epicardial Adipose Tissue as a Predictor of Substrate Distribution and Atrial Arrhythmia Recurrence in Patients with Early Atrial Remodeling.

BACKGROUND: Epicardial adipose tissue (EAT) is hypothesized to induce atrial remodeling. However, no prior studies have evaluated the spatial relationship between EAT and early atrial substrate. Given atrial fibrosis may progress from epi- to endocardium, unipolar voltage may be a more sensitive marker of early remodeling. OBJECTIVE: To evaluate the relationship between left atrial (LA) EAT, local unipolar and bipolar voltage, and post-ablation arrhythmia recurrence in patients with early atrial remodeling. METHODS: Consecutive patients underwent high-resolution LA electroanatomic mapping before index AF ablation. Patients with bipolar low voltage (≤0.5mV) area ≥5% were excluded. LA and regional unipolar scar was defined by the 5th percentile cutpoint in a healthy control cohort. EAT was segmented on pre-procedural CT. For each voltage point, EAT presence within 3 voxels was determined. Multivariable modeling was used to identify predictors of voltage at non-scar points. Atrial arrhythmia recurrence was evaluated over 12-months follow-up. RESULTS: Fifty patients (56±11 years, 78% paroxysmal) were included. Unipolar voltage cutpoints identified an additional 9.2% of points that had preserved bipolar voltages, as scar. EAT presence was a significant predictor of local bipolar voltage (p=0.010). This EAT-voltage relationship was most pronounced on the posterior wall where EAT presence predicted both unipolar (p=0.027) and bipolar (p=0.007) voltage. The posterior:LA EAT ratio was the only independent predictor of atrial arrhythmia recurrence amongst paroxysmal AF patients. CONCLUSION: EAT plays an early and likely causal role in atrial substrate development, particularly on the posterior wall. Unipolar voltage mapping may provide additive value in identifying early atrial substrate.