日本小児循環器学会雑誌 Pediatric Cardiology and Cardiac Surgery

In long QT syndrome (LQTS), torsade de pointes (TdP) sometimes develops syncope into epileptiform convulsion. Therefore, LQTS is often misdiagnosed as epilepsy, regardless of electroencephalography (EEG) findings. A school-based electrocardiographic screening program identified a 7-year-old boy who showed QT prolongation without any episodes of syncope. His sister, who was 2 years older, also showed QT prolongation. Gene analysis showed KCNQ1 mutation (LQTS type 1). We started administration of beta-blocker and recommended exercise restriction. At 10 and 12 years of age, the patient experienced episodes of syncope and tonic seizure on falling asleep. He recovered quickly from the syncope episodes, and TdP was not recognized at any point. Interictal EEG showed no seizure-related discharge after the first episode. However, some spikes were evident in the left centrotemporal area after the second episode. Subsequently, He has not presented with syncope or seizure without antiepileptic drugs for two years. The syncope episodes appeared to differ from typical LQTS type 1 attacks, which are mainly triggered by exercise and might have been associated with localization-related epilepsy. This suggests that in cases of LQTS without definite TdP, we should repeatedly evaluate EEG and seizure-related discharge to ensure that adequate pharmacotherapy (including antiepileptic drugs) is provided and inadequate exercise guidance is avoided.