Circadian and seasonal variations of ventricular tachyarrhythmias in patients with early repolarization syndrome and Brugada syndrome: analysis of patients with implantable cardioverter defibrillator.

INTRODUCTION: The circadian and seasonal patterns of ventricular tachyarrhythmia (VTA) in patients with early repolarization syndrome (ERS) have not been determined. We compared the timing of VTAs in patients with ERS and Brugada syndrome (BS).

METHODS AND RESULTS: We enrolled patients with ERS (n = 14) and BS (n = 53) who underwent implantable cardioverter defibrillator (ICD) implantation. The timing of VTAs, including cardiac arrest and appropriate shocks, was determined. During follow up of 6.4 ± 3.6 years in the ERS group and 5.0 ± 3.3 years in the BS group, 5 of 14 (36%) ERS and 10 of 53 (19%) BS patients experienced appropriate shocks (P = 0.37). Cardiac arrest showed a trend of nocturnal distribution peaking from midnight to early morning (P = 0.14 in ERS, P = 0.16 in BS). Circadian distribution of appropriate shocks showed a significant nocturnal peak in patients with ERS (P < 0.0001) but a trend toward a nocturnal peak in patients with BS (P = 0.08). There were no seasonal differences in cardiac arrest in patients with ERS and BS. However, patients with ERS showed a seasonal peak in appropriate shocks from spring to summer (P < 0.0001). There was no significant seasonal peak in patients with BS. The timing of VTAs (cardiac arrest plus appropriate shock) showed significant nocturnal distributions in patients with ERS and BS (P < 0.01, respectively). A significant clustering of VTAs was noted from spring to summer (P < 0.01) in patients with ERS, but not in patients with BS (P = 0.42).

CONCLUSIONS: Incidence of VTAs showed marked circadian variations with night-time peaks in patients with ERS and BS.