VAGAL MODULATION OF VENTRICULAR TACHYARRHYTHMIAS INDUCED BY LEFT ANSAE SUBCLAVIAE STIMULATION IN RABBITS

Previous evidence has shown that vagal nerve activity modulates ventri cular arrhythmias in patients and in animal models. However, the effec ts of direct vagus nerve stimulation on ventricular tachyarrhythmias b rought by direct sympathetic nerve stimulation have not been elucidate d. In the present study, the effects of electrical stimulation of the left cervical vagus nerve on ventricular tachycardia (VT) which was in duced by electrical stimulation of the left ansae subclaviae (LAS) in rabbits were assessed. Monophasic action potentials (MAPs) of the left ventricular endocardium were recorded simultaneously with surface EGG . In 27 rabbits tested, the stimulation of LAS induced VT in 19 rabbit s. Polymorphic VT (PVT) was induced in 14 rabbits (PVT group), whereas monomorphic VT (MVT) was induced in 5 rabbits (MVT group). Vagus nerv e stimulation during the sympathetically-induced PVT led to a restorat ion of sinus rhythm in 10 of 14 rabbits, while that during the sympath etically-induced MVT did not restore sinus rhythm in any of the 5 rabb its. Vagus nerve stimulation during the stimulation of LAS, which was of subthreshold intensity for the induction in VT, did not result in a n induction of PVT in any of the 14 rabbits in the PVT group, while it induced slow MVT in 3 of 5 rabbits in the MVT group. These results in dicate that vagus nerve stimulation preferentially exerts protective a ntiarrhythmic effects against PVT induced by sympathetic neural stimul ation in this model, while it occasionally induces slow MVT under cond itions in which sympathetic nerve activity is potentially elevated.