Low-level carotid baroreflex stimulation suppresses atrial fibrillation by inhibiting left stellate ganglion activity in an acute canine model.

Background: Low-level carotid baroreflex stimulation (LL-CBS) appears to have a potential antiarrhythmogenic effect.
Objective: The purpose of this study was to investigate effects of short-term LL-CBS on an atrial fibrillation (AF) canine model.
Methods: Group 1 (LL-CBS in the 6 hour-rapid atrial pacing model): Anesthetized dogs underwent 6 hours of rapid atrial pacing (RAP) with concomitant LL-CBS in last 3 hours (LL-CBS group; n = 7) or without (control group; n = 6). Effective refractory period (ERP), ERP dispersion, and window of vulnerability to AF were determined. Left stellate ganglion (LSG) neural activity and heart rate variability were analyzed. Group 2 (LL-CBS on electrically or mechanically induced AF with acetylcholine): In subgroup 1, sustained AF was induced by injecting acetylcholine (Ach; 10 mM) into the anterior right ganglionated plexus at baseline and after 3-hour LL-CBS (n = 7) or sham operation (n = 6). In subgroup 2, Ach was applied onto the right atrial appendage. The time of duration of AF and the average AF cycle length were determined in both subgroups.
Results: Group 1: LL-CBS reversed the RAP-induced ERP shortening and increase in ERP dispersion and window of vulnerability (P < .05). The activation of LSG, decrease in high frequency, and increase in low frequency and low frequency/high frequency ratio induced by RAP were also reversed by LL-CBS (P < .05). After 6-hour RAP, plasma norepinephrine and angiotensin II concentrations were significantly lower in the LL-CBS group than in the control group (P < .05). Group 2: The AF duration was shortened and the average AF cycle length was prolonged markedly in both subgroups (P < .01) by LL-CBS.
Conclusion: LL-CBS can reverse RAP-induced atrial electrical remodeling and suppress electrically or mechanically induced AF with Ach, and the anti-AF effect is attributed to attenuation of autonomic nerve remodeling, including inhibition of the LSG activity.
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