Abstract 2696: Decreased Sympathetic Nerve Activity Increases the Risk of Ventricular Fibrillation in Brugada Syndrome
[Background] In patients with Brugada syndrome (BS), ventricular Fibrillation (VF) occurs mainly at the nocturnal periods characterized by bradycardia, suggesting that autonomic nervous activity may be an important factor that increases the arrhythmic events. Accordingly, we examined the circadian rhythm of heart rate (HR) dynamics and variability (HRV) using Holter ECG.
[Methods] Thirty-nine consecutive BS patients were studied. Group VF(+) consisted of 11 BS with spontaneous documented VF (53.4±12.4 yrs old). Group VF(-) consisted of 28 BS without spontaneous VF (45.7±12.8 yrs old; P=NS). Circadian rhythm of HR and HRV were analyzed during 24hours and every six hours (0:00 – 6:00, 6:00–12:00, 12:00–18:00,18:00–24:00).
[Results] In Group VF(+), average HR was significantly decreased than that in Group VF(-) during 24hours, and nocturnal period (18:00–24:00). (24hours: 62.8±8.9 vs. 69.2±8.2 bpm, P<0.05 )( 18:00–24:00: 63.2±9.4 vs 70.9±9.5 bpm, P<0.05 ) Although, there was no significant difference in HF components between the groups, L/H components ratio was significantly smaller in Group VF (-) than that in Group VF (-). ( 24hours:2.8±1.6 vs 3.8±2.1 ) during 24hous and nocturnal period ( 18:00–24:00: 2.8±1.3 vs 4.3±2.2. P<0.05 ). In logistic regression analysis, decreased average HR and L/H ratio had a significant positive correlation to the spontaneous occurrence of VF (P<0.05 ).
[Conclusion]These data suggests that sinus bradycardia modulated by decreased sympathetic nerve activity increases the risk of VF occurrence in patients with Brugada syndrome.