Flecainide-induced incessant orthodromic atrioventricular reentrant tachycardia in Wolff-Parkinson-White syndrome: Uneven depression of accessory pathway conduction

Introduction During orthodromic atrioventricular reentrant tachycardia (AVRT), ventricles are activated anterogradely through the atrioventricular node and retrogradely through an accessory pathway (AP). Antiarrhythmic drugs are initially used to prevent recurrences of AVRT, whereas catheter ablation is frequently performed as a definitive treatment. Occasionally, catheter ablation can be “proarrhythmic” if the AP is partially damaged but not completely eliminated. A similar proarrhythmic effect has not been described with antiarrhythmic drugs in patients with an AP. In fact, the literature only describes the proarrhythmic effect of flecainide causing atrial flutter or ventricular tachycardia, but not the development of incessant supraventricular tachycardia in subjects with an AP. In the present report we describe a patient with Wolff-Parkinson-White syndrome due to a right paraseptal AP in whom the administration of flecainide resulted in an incessant form of AVRT resembling the permanent form of junctional reciprocating tachycardia.