Circadian pattern of fibrillatory events in non-Brugada-type idiopathic ventricular fibrillation with a focus on J waves

Background The circadian pattern of ventricular fibrillation (VF) episodes in patients with idiopathic ventricular fibrillation (IVF) is poorly understood. Objective The purpose of this study was to assess the circadian pattern of VF occurrence in patients with IVF. Methods Excluding Brugada syndrome and other primary electrical diseases, the circadian pattern of VF occurrence was determined in 64 patients with IVF. The clinical and electrocardiographic characteristics were compared among patients with nocturnal (midnight to 6:00 AM) VF and nonnocturnal VF in relation to J waves. A J wave was defined as either notching or a slur at the QRS terminal >0.1 mV above the isoelectric line in contiguous leads. Results The overall distribution pattern of VF occurrence showed 2 peaks at approximately 6:00 AM and around 8:00 PM. Nocturnal VF was observed in 20 patients (31.3%), and J waves were present in 14 of these 20 individuals (70.0%), whereas J waves were less frequent in the 44 nonnocturnal patients with VF: 16 (36.4%) ( P = .0117). Among patients with J waves, nocturnal VF was observed in 46.7% with a peak at approximately 4:00 AM. Nocturnal VF was less common in patients without J waves, occurring in only 17.6% ( P = .0124). Both the type and location of J waves and the pattern of the ST segment were similar between the nocturnal and nonnocturnal VF groups. J waves were associated with a VF storm and long-term arrhythmia recurrence. Conclusion In IVF, the presence of J waves may characterize a higher nocturnal incidence of VF and a higher acute and chronic risk of recurrence.