Long QT syndrome: Presenting as fetal bradycardia

Long QT syndromes (LQTSs) are inherited disorders of abnormal myocardial repolarization. It is characterized by prolonged QT interval, T wave abnormalities, and tachyarrhythmias such as Torsade de Pointes. Previous literature on congenital LQTS in neonates had reported presentations of cardiac arrhythmias leading to sudden death in the postnatal period. We present here a case of a neonate who presented initially with fetal bradycardia; postnatally developed ventricular tachyarrhythmias which after stabilization showed prolonged QT interval in electrocardiography leading to the diagnosis of LQTS due to a rare mutation in the ankyrin B gene. Acute ventricular tachyarrhythmia was managed with lidocaine and magnesium infusion. We used propranolol to sustain the reduction in QT interval to prevent tachyarrhythmias and Torsades de Pointes and thereby sudden death. On follow-up, the infant showed normal growth and neurodevelopment with QT interval maintained below 500 ms on propranolol prophylaxis. Fetal bradycardia can also be one of the initial manifestations of LQTS due to rare genetic mutations involving the ankyrin B gene.