Interrumption of Subintrant Episodes of Ajmaline-Induced Paroxysmal Tachycardia Due to "Fatigue" of the Retrograde Conduction in the Anomalous Pathway

pp 369-373

Abstract

A fifteen-year old patient presenting with Wolff-Parkinson-White, negative ajmaline test and frequent episodes of supraventricular orthodromic paroxysmal tachycardia was treated with amiodarone 400 mg/day. The symptoms disappeared during the following 4 years of treatment, with persistence of Wolff-Parkinson-White pattern. At nineteen, another ajmaline test showed a block of the anomalous pathway and subintrant episodes of orthodromic supraventricular paroxysmal tachycardia were observed. The episodes were interrupted by the blocking of the efferent limb of the circuit probably due to fatigue in the anomalous pathway. After five minutes the supraventricular paroxysmal tachycardia turned into atrial fibrillation with a high ventricular response and progressively increasing conduction through the accessory pathway. This arrhythmia disappeared after the IV administration of flecainide 150 mg. The importance of this case lies in the presentation of anajmaline- induced arrhythmia and shows the disease of the anomalous pathway probably favored or accelerated by chronic amiodarone therapy. The fatigue of retrograde conduction induced by ajmaline is regarded as an evidence of disease of the anomalous pathway.