Abstracts

Rationale: We report the case of a 24-year old female with a seizure disorder and previously undiagnosed long QT syndrome whose QT interval increased and developed into torsades de pointes after her levetiracetam dose was increased.Methods: Case report.Results: The patient had been having seizures since age 10, managed in her country of origin with carbamazepine with escalating doses as she grew. She initially presented to our clinic after a generalized seizure at age 24, and was started on levetiracetam 250 mg twice daily. At one-month follow up her levetiracetam level was 8.1 mcg/ml and her QT interval on EKG was 520 ms. The dose of levetiracetam was increased twice over the next month, each time after a seizure. The day after her levetiracetam was increased to 1,000 mg twice daily she presented to the emergency department with shortness of breath and an EKG showed a QT interval of 771 ms; later that morning she developed Torsades de Pointes. After stabilization and cessation of levetiracetam and carbamazepine both her drug levels and her QT interval decreased (Figure). Genetic tests showed a Met645Ile point mutation in KCNH2, which is a delayed rectifier potassium channel involved in cardiac repolarization. Mutations in KCHN2 are associated with the LQT2 syndrome, and patients can present with both long QT intervals and seizures.Conclusions: The prolongation of QT interval after increasing the levetiracetam dose was unexpected since levetiracetam has been one of the AEDs thought to have a minimal effect on QT intervals. This case raises the possibility that levetiracetam has an unanticipated effect on cardiac conduction in patients with KCNH2 mutations.