Postnatal Outcomes in Infants With a History of Fetal Supraventricular Tachycardia

Background: Fetal supraventricular tachycardia (SVT) is rare and proposed predictors of postnatal outcomes in fetal SVT have not been validated. Valid predictors can guide postnatal management. Objectives: The authors correlated fetal characteristics to the incidence of postnatal SVT and compared SVT outcomes in infants with and without a history of fetal SVT. Methods: Mother-fetus dyads with fetal SVT and a structurally normal heart were described and compared with a second cohort of infants with a postnatal diagnosis of SVT. Results: SVT was observed in 78 fetuses and 76 survived to delivery. Maternally administered transplacental antiarrhythmics were used in 49 mother-fetus dyads. Rhythm control was achieved in 37 of 49 (76%). Among fetuses with intermittent SVT, there was no ventricular dysfunction or hydrops. Postnatal SVT occurred in one-half of infants (37 of 76), and 94% presented within the first 2 days of life. The following fetal characteristics were associated with postnatal SVT on univariable analysis: sustained SVT (87% vs 56%), ventricular dysfunction (41% vs 15%), lack of conversion to sinus rhythm (49% vs 10%), and earlier gestational age at delivery (37.6 weeks vs 38.9 weeks; P ≤ 0.01 for each comparison). Compared with infants with a postnatal diagnosis of SVT, infants with a fetal diagnosis presented earlier (median age 0 days vs 17 days; P < 0.01) and had a lower incidence ventricular dysfunction at presentation (5% vs 42%; P < 0.01). Conclusions: One-half of infants with fetal SVT had postnatal SVT, nearly all within 2 days of life. These data and predictors of postnatal SVT may influence parental counseling and postnatal clinical decision-making.