The Role of Autonomic Nervous System on Right Ventricular OutflowTract Tachycardia

Background: Right ventricular outflow tract ventricular tachycardia (VT) and ventricular premature complexes (VPCs) are characterized as benign in entity with ECG morphology showing LBBB pattern and inferior axis. Pathogenic mechanisms in the genesis of RVOT VT/VPC remain largely unknown. We aimed to investigate the neural mechanism in RVOT VT/VPC in canine model. Methods: Twelve mongrel dogs (13.7 ± 1.3 Kg, 5 male dogs) were studied through midline thoracotomies. High-frequency stimulation (HFS) was applied to the proximal pulmonary artery (PA) to induce RVOT VT/VPC. An EnSite Array and a mapping catheter were used for electroanatomical mapping. The RVOT and PA were surgically excised for immunohistochemistry studies, including tyrosine hydroxylase (TH) stain for sympathetic nerves and choline acetyltransferase (ChAT) stain for parasympathetic nerves. Results: In nine (75%) out of twelve dogs, HFS of the proximal PA induced RVOT-VT/VPC. The density of THpositive nerves was significantly higher than that of ChAT-positive nerves (6803 ± 700 vs. 670 ± 252 μm2/mm2, p<0.001). Moreover, the density of TH-positive nerves was also significantly higher in the VT/VPC origin sites than that in the non-origin sites (18044 ± 2866 vs. 5554 ± 565 μm2/mm2, p=0.002). Catheter ablation of the proximal PA eliminated the inducibility of RVOT VT/VPC successfully. Conclusion: HFS of the proximal PA could induce RVOT VT/VPC. The sympathetic nerves were densely innervated to the origin of RVOT VT/VPC, indicating the critical role of sympathetic hyperactivity in the initiation and perpetuation of RVOT VT/VPC.