Fetal Supraventricular Tachycardia Treated with Transplacental Flecainide: A Case Report

Abstract

Introduction: Fetal arrhythmias occur in 1–2% of pregnancies; however, only a minority have significant clinical repercussions. Supraventricular tachycardia (SVT) is the most frequent fetal tachyarrhythmia and may be associated with hemodynamic compromise, fetal heart failure, and hydrops fetalis if not diagnosed and treated promptly. Diagnosis by fetal echocardiography and transplacental treatment are essential to improve prognosis. We describe the diagnosis, treatment, and clinical course of fetal SVT, followed by a review of recommended management. Methodology: 29-year-old primigravida at 25+1 weeks of gestation referred for suspected fetal growth restriction. The diagnosis of SVT without hydrops fetalis was made by fetal echocardiography. Hospitalization, maternal cardiologic evaluation, and transplacental treatment with Flecainide were indicated, with serial clinical and ultrasound follow-up. Results: After initiating Flecainide, normalization of the fetal heart rate was achieved within 5 days, without maternal adverse effects. Follow-up demonstrated normal fetal growth and Doppler ultrasound findings. At 31+3 weeks, the patient presented recurrence associated with threatened preterm labor, which was managed with tocolysis and antenatal corticosteroid therapy, with favorable maternal and fetal outcomes. Discussion: Transplacental pharmacologic treatment is the strategy of choice in most cases, with Flecainide considered a first-line alternative because of its high efficacy and favorable fetal bioavailability. Conclusion: Fetal SVT is a potentially serious condition that requires timely diagnosis and management. Transplacental treatment with Flecainide is an effective and safe option, especially in the absence of fetal hydrops. This case highlights the importance of a multidisciplinary approach and serial ultrasound monitoring to optimize perinatal outcomes.