Documented sudden cardiac death in prolonged QT syndrome.

Documentation of the mechanism of sudden death is described in a patient with a prolonged QT interval. Ventricular tachycardia was initiated by a ventricular premature beat (VPB) with a prematurity index similar to previous isolated VPBs. This event occurred despite the fact that the patient was receiving phenytoin sodium, a drug known to shorten the QT interval.