Abstract 1829: Circadian Changes in ST-RR and QT-RR Relationships During Daily Life of Patients with Brugada Syndrome

Abstract

In patients with Brugada syndrome, abnormal rate-dependent repolarization dynamics has been proposed as a modulating factor of arrhythmogenesis. In the present study, we assessed the hypothesis that circadian changes in both ST-RR and QT-RR relationship could relate to occurrence of ventricular fibrillation (VF) in daily life of patients with Brugada syndrome. Methods: Thirty-five male patients with Brugada syndrome who had the type I ST elevation were categorized into 14 symptomatic (with documented VF or syncope) and 21 asymptomatic groups. Unipolar V 2 and V 5 leads digital Holter ECG was recorded, and ST level in V 2 and QT interval in V 5 were automatically measured. Both ST-RR and QT-RR relationships were evaluated by means of ST-RR and QT-RR linear regression lines according to four 6-hour periods. In all 14 symptomatic patients, the time of spontaneous episodes of VF were investigated from the implantable cardioverter defibrillator stored data. Results: In symptomatic patients, ST-RR slope was highest during 18:00–24:00 and was lowest during 0:00 – 6:00; however, these circadian changes were blunted in asymptomatic patients. ST-RR intercept was not different between the 2 groups and didn’t show distinct circadian changes in both groups. The QT-RR slope was always lower, except during 6:00–12:00, in symptomatic patients than in asymptomatic patients. Circadian changes in QT-RR relationship were not evident in both groups. QT-RR intercept was not different between the 2 groups and didn’t show distinct circadian changes in both groups. Nineteen (59%) of total 32 episodes of spontaneous VF of 14 symptomatic patients occurred between 18:00 and 24:00, and 9 episodes (28%), between 0:00 and 6:00. VF seldom occurred during the daytime. Conclusions: In symptomatic patients with Brugada syndrome, a combination of augmentation of ST elevation with inhibited prolongation of QT interval during bradycardia could relate to an occurrence of VF in the late evening. Circadian Changes in ST-RR and QT-RR Slopes