Imipramine for incessant ventricular arrhythmias in 2 unrelated patients with Andersen-Tawil syndrome.

Abstract

Introduction The clinical triad of periodic muscle paralysis, ventricular ectopy, and distinctive dysmorphic features was first described by Andersen et al in 1971. In 1994, Tawil et al better defined the syndrome, currently known as AndersenTawil syndrome (ATS). Periodic paralysis in ATS might be associated with elevated, normal, or most commonly reduced serum potassium. The weakness might occur after prolonged rest or after exertion. Mild permanent weakness is common. The characteristic facial features include low-set ears, hypertelorism, and a small mandible. They also tend to be short in stature and have clinodactyly of the fifth fingers, scoliosis, and syndactyly. Mild intellectual disability is also described. The majority of patients with ATS have a mutation in the KCNJ2 gene. This group is referred to as ATS1, to differentiate it from ATS2, where no genetic cause has been identified. One prominent feature of ATS is a propensity to marked ventricular arrhythmias. These may present as frequent, isolated premature ventricular contractions (PVCs), and sometimes bidirectional or polymorphic tachycardia. Torsades de pointes (TdP) is not commonly seen. Ventricular arrhythmias tend to be slow and hemodynamically well tolerated. The density of PVCs and nonsustained ventricular tachycardia (VT) on Holter monitoring can be striking. The corrected QT (QTc) interval is generally mildly prolonged, but can be markedly so if the often prominent U waves are included in the calculation of the QTc interval. Many reports note that ventricular arrhythmias seen in ATS respond poorly to antiarrhythmic medications,