Effects of low-dose quinidine on ventricular tachyarrhythmias in patients with Brugada syndrome: low-dose quinidine therapy as an adjunctive treatment.

Quinidineis suggested as an effective agent to suppress ventricular fibrillation(VF) in the Brugada syndromeby inhibiting transient outward K + current (Ito) leading to the reduction and abbreviation of the disparity of repolarization in the right ventricular outflow region and ST segment elevation in the right precordial leads of electrocardiogram. We sought to assess the efficacy of low-dose (300-600 mg) quinidinesulfate on the prevention of ventricular fibrillationinduction by programmed electrical stimulation (PES) and spontaneous ventricular fibrillationepisodes during the subsequent follow-up period. Electrophysiologic study was performed in 14 patients with the Brugada syndrome(14 men, mean age 50 ± 11 years, range 32-75) before and during the treatment with low-dose quinidineand evaluated the efficacy of the drug therapy. Ventricular fibrillationwas induced in all the patients by programmed electrical stimulation at baseline. After oral quinidineadministration (300 mg or 600mg/d), programmed electrical stimulation was repeated. Ventricular fibrillationinduction was prevented in 6 of 14 patients (44%). Serum quinidineconcentration was higher in the patients with suppressed VF induction than those without (1.88 ± 0.44 versus 1.31 ± 0.43μg/ml, respectively). After programmed electrical stimulation, 9 of 14 patients (64%), in whom four had implantable cardioverter defibrillatorimplantation, continued to receive quinidine. During a mean follow-up period of 31 months on quinidine, no side effects except one with diarrhea were observed (12.5%). There were no ventricular fibrillationrecurrences in 3 of the 9 patients, who had frequent implantable cardioverter defibrillatordischarges due to ventricular fibrillationattacks before treatment with quinidine. Low-dose quinidinehas a potential as an adjunctive therapy for patients of the Brugada syndromewith frequent implantable cardioverter defibrillatordischarges.