Chronic Intermittent Low Level Stimulation of Tragus Reduces Cardiac Autonomic Remodeling and Ventricular Arrhythmia Inducibility in a Post Infarction Canine Model.
OBJECTIVES This study investigated whether chronic low level tragus stimulation (LL TS) inhibits cardiac sympathetic remodeling and reduces ventricular arrhythmia inducibility in a post infarction canine model. BACKGROUND Low level vagal stimulation has been shown to suppress cardiac sympathetic activity, which plays an important role in ventricular arrhythmia after myocardial infarction (MI) Our previous studies reported a noninvasive approach to deliver vagal stimulation by transcutaneous stimulation at the tragus, where the auricular branch of the vagus nerve is located. METHODS Twenty two beagles were randomized to the normal control (n 6) MI (left anterior descending coronary artery ligation without LL TS [n 8] and TS (MI plus LL TS [n 8] groups. LL TS was delivered 2 h each day at 80% below the threshold which slowed sinus rate. RESULTS At 2 month follow up, LL TS was found to significantly reduce ventricular arrhythmia inducibility (arrhythmia score: 1.8 0.8 vs. 3.6 0.7, p 0.01, compared to the MI group) decreased left stellate ganglion (LSG) activity (frequency: 32 15 vs. 112 29 impulses/s; and amplitude: 0.15 0.12 mV vs. 0.38 0.12 mV, compared to MI group) and attenuated cardiac sympathetic remodeling induced by chronic MI. The nerve growth factor (NGF) protein was down regulated, whereas the small conductance calcium activated potassium channel type2 (SK2) protein was up regulated in the LSG by chronic LL TS. CONCLUSIONS Chronic LL TS could reduce the ventricular arrhythmia inducibility, LSG neural activity and sympathetic neural remodeling in a post infarction canine model. Down regulation of NGF protein and up regulation of SK2 protein in the LSG contribute to the salutary effects of LL TS.
JACC. Clinical electrophysiology