Abstract 3324: Intravenous Administration of Quinidine Gluconate Prevents Induction of Ventricular Fibrillation in Patients with Brugada Syndrome
Background: Many investigators believe that the implantable cardioverter defibrillator is the only effective therapy for asymptomatic high-risk patients with Brugada syndrome (BS) and inducible ventricular fibrillation (VF). However, quinidine (QND) is a potential alternative therapy for BS because it inhibits the prominent transient outward K+ current (Ito) in the right ventricular (RV) epicardium which is assumed to be responsible for BS.
Purpose: The electrophysiological effects of intravenous administration of quinidine gluconate on inducible VF in patients with BS were evaluated.
Methods: Electrophysiological study was performed in seven asymptomatic BS patients with type 1 ECG (n=4, 4 male, age: 56±12 years) and type 2 ECG which changed to type 1 ECG by administration of classic antiarrhythmic drug, pilsicainide (n=3, 3 male, age: 49±7 years). Programmed ventricular stimulation (PVS) was performed by delivering up-to 2 extrastimuli from 2 RV apex and outflow tract at pacing cycle lengths of 600 and 400msec. Intravenous QND gluconate (5mg/kg±10 mg/min) was given to all patients. Mean serum QND concentration was 3.1±0.56μg/ml. The effects of QND on arrhythmia inducibility and RV outflow tract (OT) monophasic action potential (MAP) duration were tested. The maximum slope of the RVOT MAP restitution curve (Slopemax) was obtained by delivering a single extra-stimulus at a cycle length of 600msec.
Results: All patients had inducible sustained polymorphic VT/VF with PVS at baseline. No sustained ventricular tachyarrhythmias could be induced with intravenous QND in all patients. QND increased RVMAPD at 90% repolarization at a cycle length of 600 msec from 217.7±5.0msec to 260±4.6msec (p<0.01). QND increased effective refractory period of RVOT from 210 ± 18 msec to 248±15 msec (p<0.01) and also increased RVOT MAP duration at the shortest coupling interval from 134±15msec to 191±32msec (p<0.01). QND decreased Slope max from 1.26±0.89 to 0.97±0.59 (p<0.05).
Conclusion: Quinidine is highly effective in preventing VF induction in asymptomatic high-risk BS patients by increasing ERP and MAP duration at baseline, increasing MAP duration at the shortest coupling interval and decreasing the maximum slope of the MAP restitution curve in the RVOT.