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.