Exaggerated Reactivity of Parasympathetic Nerves Is Involved in Ventricular Fibrillation in J‐Wave Syndrome

Reactivity of Vagal Nerves Is Involved in VF Introduction Brugada syndrome (BrS) and early repolarization syndrome (ERS) are termed the J‐wave syndrome. In most cases of J‐wave syndrome, ventricular fibrillation (VF) often occurs around midnight or in the early morning when parasympathetic tone is augmented. Objective The purpose of this study was to clarify the relationship between VF and autonomic nervous activity in patients with J‐wave syndrome. Methods and Results We enrolled 28 consecutive patients with J‐wave syndrome (20 BrS and 8 ERS) in whom implantable cardioverter defibrillators (ICDs) were implanted between January 2002 and December 2014. Eleven patients (39%) experienced ICD shock delivery due to VF recurrence after ICD implantation (recurrent‐VF group). We investigated baroreflex sensitivity (BRS) using the phenylephrine method, heart rate variability (HRV) with Holter electrocardiography, plasma levels of norepinephrine, and cardiac 123 I‐metaiodobenzylguanidine (MIBG) scintigraphy to estimate autonomic nervous function. Upon measurement of HRV, plasma levels of norepinephrine, and 123 I‐MIBG testing, there was no significant difference between recurrent‐VF and nonrecurrent‐VF groups. However, BRS was significantly higher in the recurrent‐VF group than in the nonrecurrent‐VF group (P = 0.03). Kaplan–Meier curves suggested that high‐BRS patients had higher VF recurrence than those with nonhigh‐BRS (P = 0.04). Cox proportional hazards regression analyses showed that high BRS was associated independently with VF recurrence (P = 0.002). Conclusions Our results suggest that exaggerated reactivity of parasympathetic nerves, as represented by increased BRS, may underlie VF in patients with J‐wave syndrome.