Management of Fetal Supraventricular Tachycardia: Case Series from a Tertiary Perinatal Cardiac Center

BACKGROUND: Fetal supraventricular tachycardia is a relatively uncommon cardiac rhythm abnormality which is often associated with adverse perinatal outcomes if untreated. Although there are several treatment modalities and protocols in use globally, there is no consensus as to the most effective antiarrhythmic to manage this condition. AIM: This study aimed to evaluate perinatal outcomes following prenatal maternal therapy for fetal supraventricular tachycardia. MATERIALS AND METHODS: This was a 20-year retrospective cohort study. Institutional records were reviewed for antenatal therapy choice and maternal and fetal outcomes. RESULTS: Sixty-nine cases met diagnostic criteria for fetal SVT, of which 56 (81%) received maternal antiarrhythmic therapy. Digoxin was the most common, but least effective, first-line therapy in 28 patients, achieving successful rate reversion in 35.7%. Thirty-one patients (55%) required second-line therapy, and this was most successful with digoxin and flecainide polytherapy achieving rate reversion in 17 of 18 cases (94.5%) at a median of 3 days (1.5-7). Hydrops was present in 23 (33%) cases at initial presentation, 16 of which achieved rate reversion. There was minimal difference in treatment efficacy comparing single- or multiple-agent treatment in the setting of hydrops (50% vs. 42.8%). Side effects occurred in 14/56 treated patients (25%) but were severe in only 8 (14.3%) women, most commonly with digoxin and flecainide polytherapy (6 of 8 cases). There were 3 (4%) fetal deaths amongst the study cohort. CONCLUSIONS: Digoxin and flecainide polytherapy were well tolerated and successfully achieved rhythm and rate control in fetuses with prenatally diagnosed supraventricular tachycardia. The presence of hydrops was a poor prognostic feature.