Postnatal Outcomes of Fetal Supraventricular Tachycardia: a Multicenter Study

Supraventricular tachycardia (SVT), the most common fetal tachycardia, can be difficult to manage in utero. We sought to better understand predictors of the postnatal clinical course in neonates who experienced fetal SVT. We hypothesized that fetuses with hydrops or those with refractory SVT (failure of first-line SVT therapy) are more likely to experience postnatal SVT. This was a retrospective multicenter cohort study of subjects diagnosed with fetal SVT between 2006 and 2014. Fetuses with structural heart disease were excluded. Descriptive comparative statistics and univariate analysis with logistic regression were utilized to determine factors that most strongly predicted postnatal SVT and preterm delivery. The cohort consisted of 103 subjects. Refractory SVT was found in 37% (N = 38) of the cohort with this group more likely to be delivered prematurely (median = 36 vs. 37.5 weeks, p = 0.04). Refractory SVT did not increase the risk of postnatal SVT (p = 0.09). Postnatal SVT was seen in 61% (N = 63). Of those, 68% (N = 43) had postnatal SVT at ≤2 days of age. Postnatal SVT was associated with a later fetal SVT diagnosis (median = 30 vs. 27.5 weeks, p = 0.006). We found a strong correlation between postnatal SVT and later gestational age at fetal SVT diagnosis. Subjects with refractory SVT or hydrops did not have a higher risk of postnatal SVT. We propose strong consideration for term delivery in the absence of significant clinical compromise. Further studies to assess whether outcomes vary for preterm delivery versus expectant management in those with refractory SVT should be performed.