Delayed sodium channel inactivation mimics long QT syndrome 3.

DPI 201-106 delays sodium channel inactivation. Acute administration of DPI 201-106 prolonged the QT interval, provoked spontaneous torsades de pointes in one patient, and facilitated stimulation-induced polymorphic ventricular tachyarrhythmias in two patients. Similar to the observations in animal studies, delaying sodium channel inactivation is a new form of the acquired long QT syndrome, mimicking long QT syndrome type 3.