Epilepsy Misdiagnosed as Long QT Syndrome: It Can Go Both Ways

Cardiogenic seizures are common and could be the sentinel event heralding the presence of congenital long QT syndrome (LQTS). Distinguishing a cardiogenic seizure from a neurogenic one is of the utmost importance. Herein, we present the case of a 12‐year‐old boy with recurrent episodes of syncope and seizures. Despite absence of QT prolongation on electrocardiogram, absence of documented arrhythmias, a negative LQTS genetic test, and recurrent episodes while on nadolol beta‐blocker therapy, he was diagnosed with LQTS and implanted with an implantable cardioverter defibrillator (ICD). When syncope and seizure occurred with normal sinus rhythm documented on the ICD, he was referred to neurology, and an electroencephalogram was positive for numerous bursts of bilaterally synchronous generalized discharges. He was started on antiepileptic treatment after which his seizures resolved. His LQTS diagnosis was removed, beta‐blocker therapy discontinued, and his ICD was explanted. He has been seizure‐free for over 2 years.     

Efficacy of Ventricular Pacing in the Treatment of an Arrhythmic Storm Associated with a Congenital Long QT Mutation

Long QT syndrome in the infant with 2:1 atrioventricular block is a malignant form of disease associated with frequent torsade de pointes in some cases. Those patients that do not respond to antiarrhythmic therapy are particularly challenging to manage. Ventricular pacing in this patient population has been shown to reduce arrhythmic events. We report a case of a newborn with frequent torsade de pointes requiring defibrillation and cardiopulmonary resuscitation with immediate shortening of the QTc interval with ventricular pacing and subsequent resolution of torsade de pointes.     

Congenital long QT syndrome: Severe Torsades de pointes provoked by epinephrine in a digenic mutation carrier

Congenital Long QT Syndrome (LQTS) is a potentially lethal cardiac channelopathy characterized by prolongation of the corrected QT (QTc) interval on the surface electrocardiogram. The hallmark phenotypic features are syncope, seizure or sudden death, however most of the mutation carriers are asymptomatic and their risk for arrhythmias such as Torsade de pointes (TdP) are low. We report a case of Long QT syndrome with a corrected QT of 520 ms. For symptom – arrhythmia correlation a loop recorder was implanted with no documented arrhythmias. Epinephrine testing was performed for clinical risk stratification leading to Torsades de pointes during recovery phase which required defibrillation. Genetic testing discovered two pathogenic heterozygous mutations in two different LQT genes (SCN5A and KCNQ1). We propose a calcium homeostasis mechanism for the interaction of both mutations that exaggerated the phenotype, while each mutation by itself is causing a relatively modest phenotype.