Study population
We enrolled 50 consecutive patients, between 2003 and 2018, who were referred to our institution for resuscitated VF not linked to structural heart disease. IVF was diagnosed in 35 patients and BrS was diagnosed in other 15 patients. During hospitalization, all patients received implantable cardioverter defibrillator (ICD) therapy. Patients with structural heart disease were excluded using 12-lead ECGs, transthoracic echocardiography, cardiac computed tomography, cardiac magnetic resonance imaging, coronary arteriography including spasm induction, and left ventriculography. Patients with long QT syndrome, short QT syndrome, and catecholamine-induced polymorphic ventricular tachycardia were also excluded. Institutional review board approval was obtained.
All patients without spontaneous type 1 Brugada ECGs received sodium channel blocker test. BrS was diagnosed when type 1 ST-segment elevation was observed either spontaneously or during sodium channel blocker test in at least one right precordial lead (V1 and V2), which was placed in a baseline standard or high (second or third) intercostal space.10
Twelve-lead ECGs recorded in the absence of antiarrhythmic drugs were compared between patients with IVF and control subjects who were matched to patients based on gender and age (patient: control ratio, 1:3). Control subjects without cardiovascular disease or medication use were included. Subjects with bundle branch block, intraventricular conduction disturbances, and/or abnormal QT intervals in ECGs were excluded.