Favorable neurodevelopmental outcome in a hypothyroid neonate following intracordal amiodarone for cardioversion of refractory supraventricular tachycardia in a fetus

Fetal supraventricular tachycardia (SVT), characterized by a fetal ventricular heart rate faster than 200 beats per minute (bpm), is often diagnosed during routine fetal heart monitoring or prenatal ultrasound examinations. Clinical guidelines for management of fetal SVT have not been determined in standardized trials, nor do we have a clear sense regarding the long-term developmental outcomes and side effects of in utero antiarrhythmic therapy. We describe our approach to the treatment of refractory SVT in a fetus with hydrops using direct umbilical vein treatment with amiodarone coupled with effusion evacuation. We successfully achieved in utero resolution of SVT. There was transient amiodarone-induced hypothyroidism, which we screened for early and treated with Synthroid. Ultimately our patient had normal long-term growth and development as measured by modified Denver office checklists and Ages and Stages questionnaires. Our experience advocates for vigilant screening and management of hypothyroidism in fetuses exposed to in utero amiodarone and suggests that it is possible to achieve good outcomes in high-acuity refractory cases of SVT.