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.