A Case of Idioventricular Fibrillation Associated with J Waves rather than Intermittent WPW Syndrome

A 35-year-old man who had shown intermittent Wolf-Parkinson-White (WPW) syndrome and a history of syncope in the early morning was admitted to our hospital for the treatment of WPW syndrome. Ventricular fibrillation (Vf) as the cause of syncope was confirmed by the emergency crews and he was successfully resuscitated using an automatic external defibrillator. He fortunately recovered without any neurological complication. Ischemic heart disease had already been ruled out. He had been suspected as Vf due to atrial fibrillation associated with WPW syndrome and amiodarone had been started. Terminal QRS notches (J wave) in V3–V5 without delta wave were observed in his ECG upon admission. Electrophysiological study revealed the appearance of delta wave after isoproterenol infusion. Effective refractory period of antegrade Kent bundle was more than 600 msec, suggesting that intermittent WPW syndrome could not be a cause of Vf. Vf was easily induced by right ventricular extrastimuli after Kent ablation. We finally diagnosed idiopathic Vf with J wave. Therefore, we implanted an intracardiac defibrillator (ICD) and substituted cibenzoline for amiodarone. He has never experienced shock during 10 months after ICD implantation. We report a case here that the cause of syncope was thought to be an idiopathic Vf associated with J waves rather than a Vf due to atrial fibrillation associated with intermittent WPW syndrome.