Clinical data
The medical records of all VF patients were investigated for age at VF development, sex, family history of sudden death at ≤ 45 years, patient’s activity at the onset of VF, and medications. Activity status at the onset of VF was classified as sleep if VF occurred during sleeping, arousal at rest if VF occurred when the patient was awake without body movement, or physical effort if VF occurred during exertion. Electrophysiologic studies were performed on 27 patients.
After ICD implantation, all patients visited the outpatient clinic every 3–6 months for ICD interrogation. During the follow-up, patients were considered to have VF recurrence if VF was documented by ICD interrogation. An electrical storm was defined as three or more VF events recorded within 24 hours. The beginning of the observation period was the day of ICD implantation. ECGs were recorded in the 3rd and 4th ICSs at clinic visits; however, none of the patients diagnosed with IVF showed type 1 Brugada ECGs during the follow-up.