Postnatal Outcomes in Infants WithaHistory of Fetal SupraventricularTachycardia.

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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. 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. 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. 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 2days 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 (37.6weeks vs 38.9weeks; P≤ 0.01 for each comparison). Compared with infants with a postnatal diagnosis of SVT, infants with a fetal diagnosis presented earlier (median age 0days vs 17days; P< 0.01) and had a lower incidence ventricular dysfunction at presentation (5% vs 42%; P< 0.01). One-half of infants with fetal SVT had postnatal SVT, nearly all within 2days of life. These data and predictors of postnatal SVT may influence parental counseling and postnatal clinical decision-making.