Acquired long QT syndrome and ventricular tachycardia in a patient on flecainide therapy.

This case report describes a 54-year-old man presenting with loss of consciousness due to acquired long QT syndrome shortly after flecainide therapy. The patient had no common risk factors for acquired long QT syndrome. Prior to onset of ventricular tachycardia, bradyarrhythmia and short-long-short sequence were observed with a prolonged QT interval of 710 ms. However, the morphology of induced tachycardia was uniform rather than torsades de pointes. We presumed that the properties of flecainide, such as slowing conduction, contribute partly in a use-dependent manner to development of uniform tachycardia. In addition, we believe that prolongation of QT by flecainide is exceedingly rare; however, it may be one of the mechanisms of flecainide-induced proarrhythmia.