Effect of Epicardial Fat Pad Ablation on Acute Atrial Electrical Remodeling and Inducibility of Atrial Fibrillation

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Background: Atrial electrical remodeling (AER) is the underlying mechanism of atrial fibrillation (AF). The present study investigated the impact of epicardial fat pad (FP) ablation on acute AER (AAER) and inducibility of AF. Methods and Results: AAER was performed in 28 mongrel dogs through 4-h rapid atrial pacing (RAP). Before RAP, 14 dogs (ablation group) underwent FP ablation, and the other 14 (control group) underwent a sham procedure. The atrial effective refractory period (ERP) and vulnerability window (VW) of AF were measured with and without bilateral cervical vagosympathetic nerve stimulation (VNS) at the high right atrium, ostium of the coronary sinus (CS) and distal CS before and after every hour of RAP. In the control group, ERP was markedly shortened in the first 2 h of RAP and then stabilized. AF was only slightly induced. After RAP, the time course of ERP with and without VNS was similar. VNS significantly shortened ERP and increased VW before and after RAP. In the ablation group, ERP was significantly prolonged after FP ablation. Moreover, neither VNS nor RAP shortened the ERP or increased the VW. AF could not be induced (VW=0). Conclusions: RAP resulted in AAER, which may be mediated and aggravated by autonomic activity. Epicardial FP ablation generated denervation, which not only abolishes AF inducibility but also prevents RAP-mediated AAER.