Electrophysiologic characteristics of an Andersen syndrome patient with KCNJ2 mutation.

We report the first case of a patient with Andersen syndrome in whom electrophysiologic study was performed. The patient was a 19-year-old woman with familial periodic paralysis, abnormal QT-U complex, and nonsustained ventricular tachycardia. Mutation analysis revealed a missense mutation in KCNJ2, a component of Kir2.1. Monophasic action potential recordings showed a delayed afterdepolarization (DAD)-like hump in the left ventricle. Initiation of epinephrine-induced premature ventricular contractions always coincided with both the exaggerated DAD-like hump and the U wave. These findings suggest that reduced Kir2.1 current contributes to the development of DAD and ventricular arrhythmias in Andersen syndrome.