Published Online
on October 2, 2009

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Original Article

Low Level Vagosympathetic Stimulation: A Paradox and Potential New Modality for the Treatment of Focal Atrial Fibrillation

Shuyan Li¹; Benjamin J. Scherlag²; Lilei Yu²; Xia Sheng²; Ying Zhang²; Reza Ali²; Yumei Dong²; Muhammad Ghias² and Sunny S. Po^2,3

¹ The Second Hospital of Jilin University, Jilin, China;
² University of Oklahoma Health Sciences Center, Oklahoma City, OK

^* Corresponding author; email: sunny-po{at}ouhsc.edu

Background—We used high frequency stimulation (HFS) delivered during the refractory period of the atrium (A) and pulmonary veins (PVs) to induce focal firing and atrial fibrillation (AF). This study was designed to demonstrate that bilateral low-level vagosympathetic nerve stimulation (LL-VNS) could suppress HFS induced focal AF at atrial and PV sites.

Methods and Results—In 23 dogs, anesthetized with Na-pentobarbital, electrodes in the vagosympathetic trunks allowed LL-VNS at 1 volt below that which slowed the sinus rate or atrioventricular conduction. Multi-electrode catheters were fixed at right and left superior and inferior PV (RSPV, RIPV, LSPV, LIPV) and both atrial appendages (AA). LL-VNS continued for 3 hours. At the end of each hour, the HFS algorithm consisting of a 40 ms train of stimuli, (200 Hz, stimulus duration 0.1-1.0 msec) was delivered 2 ms after the atrial pacing stimulus during the refractory period at each PV and AA site. The lowest voltage of HFS that induced AF was defined as the AF threshold (AF-TH). Five dogs without LL-VNS served as sham controls. Six dogs underwent LL-VNS but after transection of bilateral vagosympathetic trunks. LL-VNS induced a progressive increase in AF-TH at all PV and AA sites, particularly significant (p<0.05) at RSPV, RIPV, LSPV and right AA. Bilateral vagosympathetic transection did not significantly alter the previous findings and the 5 sham controls did not show changes in AF-TH at all sites over 3 hours.

Conclusions—LL-VNS may prevent episodic AF due to rapid PV and non-PV firing.

Key Words: arrhythmia • nervous system, autonomic • vagus nerve • Atrial Fibrillation • vagal stimulation