Influence of ablated cardiac fat pad on atrial fibrillation induced by a single extra-stimulus in dogs

Objective: To study the influence of ablated cardiac fat pad on atrial fibrillation induced by a single extra-stimulus in dogs. Metbods: Twenty-two dogs were anesthetized and their chest cavity was openned through a median sternotomy (2 dogs died of fibrillation immediately after opening) to expose the 3 cardiac fat pads: the medial superior vena cava and aortic root fat pad (SVC-Ao FP), the right pulmonary vein-atrial junction fat pad (RPV FP), and the inferior vena cava-left atrial junction fat pad (IVC-LA fat pad). The atrial effective refractory period (AERP), dispersion of AERP (dAERP), and pulmonary vein effective refractory period (PVERP) were measured under baseline and after ablation of the 3 fat pads. The left superior pulmonary veins were stimulated by S₁S₁ bursting stimulation and S₁S₂ program stimulation to induce atrial fibrillation before and after ablation. Results: After ablation, AERP increased from (137±16) ms to (147±16) ms and PVERP increased from (131±14) ms to (141+9) ms, while dAERP decreased from (17.0±4.6) ms to (12.0±4.3) ms (P<0.05). After ablation, S₁S₁ cycle length decreased from (173+25) ms to (145±21) ms when used for restimulation after ablation (P<0.05 ). S₁S₂ could not induce AF again. Conclusion: Ablation of the 3 cardiac fat pad can influence the electrical remodeling of the atrial and the pulmonary vein, which may hamper the induction of atrial fibrillation.