Abstract 2697: Blunted Response of Vagal- and Bradycardia-Induced QT prolongation Induces Ventricular Fibrillation in Patients with Brugada Syndrome
[Background] It has been reported that autonomic nervous activity, especially increased vagal activity, is an important factor that increases ventricular fibrillation (VF) in Brugada syndrome (BS). It has been also reported that vagal activity influences QT interval as well as RR interval. Accordingly, we examined the dynamic changes of QT and RR intervals with vagal activity that defined heart rate variability (HRV) using Holter ECG.
[Methods] Total forty BS patients with VF (n=11, 53.4±12.4 yrs.), without VF (n=29, 45.4±12.4 yrs.) were studied. QT, RR intervals, and high frequency (HF) components of HRV (LnHF; 0.15– 0.40 Hz) were obtained from Holter recordings. Circadian rhythm of QT/RR and QT/LnHF relationships were analyzed during 24-hours and every six hours.
[Results] The slope of QT/RR were significantly decreased in GroupVF(+) during 24-hours and nocturnal periods(0:00 – 6:00, 18:00–24:00). The slope of QT/LnHF were significantly decreased in GroupVF(+).
[Conclusion] These data demonstrates that bradycardia-induced QT prolongation during night period was significantly suppressed in VF(+) of BS patients. Blunted response of QT interval to the vagal activity may be associated with VF occurrence in BS.