A long journey to birth: a case of refractory fetal SVT

Abstract

Fetal tachyarrhythmias occur in approximately 0.4-0.6% of pregnancies, with supraventricular tachycardia (SVT) representing the most common subtype. Although digoxin has traditionally been used as first-line therapy, accumulating evidence indicates that monotherapy is frequently insufficient, particularly in sustained or accessory pathway–mediated SVT. Nevertheless, the optimal timing and escalation strategy for combination therapy remain controversial. We report a case of sustained fetal SVT diagnosed at 29 weeks of gestation in a non-hydropic fetus, managed using a response-guided, stepwise escalation approach. Initial dual transplacental antiarrhythmic regimens failed to achieve sinus rhythm despite therapeutic maternal drug levels and close surveillance. Owing to persistent tachycardia, triple therapy with digoxin, sotalol, and flecainide was initiated under intensive maternal–fetal monitoring, resulting in successful and sustained conversion to sinus rhythm without maternal or fetal adverse effects. This case underscores the importance of individualized, decision-oriented treatment escalation rather than prolonged reliance on monotherapy. Careful maternal electrocardiographic monitoring combined with serial fetal echocardiography enabled the safe administration of triple therapy and was associated with a favorable perinatal outcome.