Paradoxical long-term proarrhythmic effects after ablating the head station ganglionated plexi of the vagal innervation to the heart

Background: The ganglionated plexi (GP) located at the junction of the superior vena cava, aorta, and right pulmonary artery (SVC-Ao GP) was proposed to be the head station between the extrinsic and the intrinsic cardiac autonomic nervous system (ECANS and ICANS, respectively). Objective: To investigate the chronic effects after interrupting the ECANS-ICANS connections by ablating the SVC-Ao GP. Methods: A right thoracotomy in 10 dogs allowed stimulation at the right superior and inferior pulmonary veins (RSPV and RIPV, respectively), right atrial appendage (RAA), and SVC to determine effective refractory period (ERP) and atrial fibrillation (AF) inducibility in the first operation. Group 1 (n = 5) received SVC-Ao GP ablation; group 2 (n = 5) received no ablation. A second operation and the same measurements were made 10 weeks later. A pacemaker with lead implanted at the RSPV recorded atrial fibrillation or tachycardia (AF/AT). Results: During the first operation in group 1, ERPs increased significantly in the SVC but not at the RSPV, RIPV, or RAA site immediately after ablation, whereas ERPs decreased significantly in the RSPV, RIPV, and RAA but not the SVC in the second operation performed 10 weeks later (compared to the ERP in the first operation). ERPs decreased and AF/AT burden increased significantly from weeks 4 and 5, respectively, after the first operation in group 1 dogs. The ERP and AF/AT burden in group 2 remained unchanged between operations. Conclusions: Ablation of the head station GP between the ECANS and the ICANS prolonged the ERP acutely, but shortened regional ERPs and increased AF/AT burden chronically, suggesting that the ECANS may tonically inhibit the ICANS activity.