Heart failure (HF) is associated with a high incidence of ventricular tachycardia (VT) and fibrillation (VF). Patients with HF in whom these lethal arrhythmias can be induced by electrophysiological (EP) testing carry a high risk of sudden cardiac death. We showed that chronic electrical carotid baroreflex activation therapy (BAT) with the Rheos® System (CVRx, Inc.) improves LV function, attenuates LV remodeling and restores autonomic sympathetic-parasympathetic balance in dogs with HF. This study examined the effects of long-term therapy with BAT on the induction of VT or VF in dogs with coronary microembolization-induced HF (LV ejection fraction ~20%). Eleven dogs with HF underwent EP testing at baseline prior to therapy and after 3 and 6 months of therapy with BAT and again 6 weeks after withdrawal of BAT therapy (n = 7) or no therapy at all (Control, n = 4). Programmed ventricular stimulation was performed from the right ventricular apex and included delivery of up to 4 extrastimuli at progressively shorter coupling intervals (in steps of 10 msec). The extrastimuli were delivered following 8 ventricular paced beats with a drive cycle length between 600 and 200 msec. If a sustained monomorphic VT or VF could not be induced, isoproterenol infusion was initiated to increase the sinus rate by ~30% and the EP stimulation protocol was repeated. At baseline, a sustained VT or VF was induced in all 11 dogs (100%). After 3 and 6 months of follow-up, all Control dogs (100%) were induced into sustained VT or VF. After 3 months of BAT, only 3 of 7 dogs (43%) were induced into sustained VT or VF. After 6 months of BAT, only 2 of 7 dogs (29%) were induced into sustained VT or VF. Finally after withdrawal of BAT therapy, all dogs (100%) were again induced into systained VT or VF. In addition to improving LV function and attenuating LV remodeling, long-term monotherapy with BAT markedly increases the threshold for lethal ventricular arrhythmias in dogs with chronic HF. This is a marked improvement over inducibility of lethal arrhythmias seen in historical untreated controls. This benefit of BAT supports the continued exploration of this device as a therapeutic modality for treating patients with chronic HF and increased risk of sudden cardiac death.
