Abstract 1829: Circadian Changes in ST-RR and QT-RR Relationships During Daily Life of Patients with Brugada Syndrome
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 V2 and V5 leads digital Holter ECG was recorded, and ST level in V2 and QT interval in V5 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.