Low-level transcutaneous electrical stimulation of the auricular branch of the vagus nerve: A noninvasive approach to treat the initial phase of atrial fibrillation

BACKGROUND We studied the effects of transcutaneous electrical stimulation at the tragus, the anterior protuberance of the outer ear, for inhibiting atria L fibrillation (AF). OBJECTIVE To develop a noninvasive transcutaneous approach to deliver Low-eve L vagal nerve stimulation to the tragus in order to treat cardiac arrhythmias such as AF. METHODS In 16 pentobarbital anesthetized dogs, multielectrode catheters were attached to pulmonary veins and atria. Three tungsten-coated microelectrodes were inserted into the anterior right ganglionated plexi to record neural activity. Tragus stimulation (20 Hz) in the right ear was accomplished by attaching 2 alligator dips onto the tragus. The voltage stowing the sinus rate or atrioventricular conduction was used as the threshold for setting the Low-eve L tragus stimulation (LL-TS) at 80% below the threshold. At baseline, programmed stimulation determined the effective refractory period (ERP) and the window of vulnerability (WOV), a measure of AF inducibility. For hours 1-3, rapid atria L pacing (RAP) was applied atone, followed by concomitant RAP LL-TS for hours 4-6 (N = 6). The same parameters were measured during sinus rhythm when RAP stopped after each hour. In 4 other animals, bivagal transection was performed before LL-TS. RESULTS During hours 1-3 of RAP, there was a progressive and significant decrease in ERP, increase in WOV, and increase in neural activity vs baseline (all P < .05). With RAP LL-TS during hours 4-6, there was a Linear return of ERP, WOV, and neural activity toward baseline leveLs (all P < .05, compared to the third-hour values). In 4 dogs, bivagal transection prevented the reversal of ERP and WOV despite 3 hours of RAP LL-TS. CONCLUSIONS LL-TS can reverse RAP-induced atria L remodeling and inhibit AF inducibility, suggesting a potential noninvasive treatment of AF.