Atypical proarrhythmia with dofetilide: monomorphic VT and exercise-induced torsade de pointes.

Proarrhythmia with dofetilide has most typically taken the form of torsade de pointes (TdP) and generally occurs early with therapy, such that in-hospital initiation of dofetilide with 3 days of continuous electrocardiogram monitoring is recommended. This article reports two unusual variants of ventricular proarrhythmia with dofetilide: (1) nonsustained runs of monomorphic ventricular tachycardia shortly after taking the first dose of dofetilide, confirmed by rechallenge; and (2) TdP that followed the development of isolated ventricular premature beats during an exercise test in a patient with neither excessive QT prolongation on dofetilide nor any ectopy whatsoever during in-hospital telemetric monitoring but with significant QT interval prolongation after the postectopic pause. These cases demonstrate that clinicians must be alert to the appearance of proarrhythmia with dofetilide at times other than early during drug initiation if the electrophysiological milieu is altered during nonhospital activity and/or of a pattern other than TdP.