Background:Shensong Yangxin (SSYX),a traditional Chinese herbal medicine,has long been used clinically to treat arrhythmias in China.However,the mechanism of SSYX on atrial fibrillation (AF) is unknown.In this study,we tested the hypothesis that the effect of SSYX on the progression of paroxysmal AF is correlated with the regulation of autonomic nerve activity.Methods:Eighteen mongrel dogs were randomly divided into control group (n =6),pacing group (n =6),and pacing + SSYX group (n =6).The control group was implanted with pacemakers without pacing;the pacing group was implanted with pacemakers with long-term intermittent atrial pacing;the pacing + SSYX group underwent long-term intermittent atrial pacing and SSYX oral administration.Results:Compared to the pacing group,the parameters of heart rate variability were lower after 8 weeks in the pacing + SSYX group (low-frequency [LF] component:20.85 ± 3.14 vs.15.3 ± 1.89 ms2,P =0.004;LF component/high-frequency component:1.34 ± 0.33 vs.0.77 ± 0.15,P ＜ 0.001).The atrial effective refractory period (AERP) was shorter and the dispersion of the AERP was higher after 8 weeks in the pacing group,while the changes were suppressed by SSYX intake.The dogs in the pacing group had more episodes and longer durations of AF than that in the pacing + SSYX group.SSYX markedly inhibited the increase in sympathetic nerves and upregulation of tumor necrosis factor-alpha and interleukin-6 expression in the pacing + SSYX group.Furthermore,SSYX suppressed the decrease of acetylcholine and α7 nicotinic acetylcholine receptor protein induced by long-term intermittent atrial pacing.Conclusions:SSYX substantially prevents atrial electrical remodeling and the progression of AF.These effects of SSYX may have association with regulating the imbalance of autonomic nerve activity and the cholinergic anti-inflammatory pathway.