Intrauterine supraventricular tachycardia.

Six examples of intrauterine supraventricular tachycardia together with 31 previously reported cases are described and analyzed. Among the 37 infants, structural heart disease was present in only four (11%), three of whom died. Males comprised 68% of the group without identifiable heart disease or pre-excitation. Congestive heart failure was evident in 62% of the infants at birth or shortly thereafter; ascites was the predominant finding in three (8%). Neither the duration of SVT nor heart rate was predictive of the clinical status at birth. Infants without underlying heart disease or conduction abnormalities had a benign course after the neonatal period. Thirty-eight percent of the babies converted to sinus rhythm during or shortly after delivery without medication, and most of the others converted after digitalization. The failure of maternal digitalization to convert SVT to sinus rhythm in two of our infants was perhaps related to subtherapeutic maternal and fetal digoxin levels. Newborn infants presenting with unexplained ascites or congestive heart failure should have an ECG to determine whether pre-excitation is present, and their cardiac rhythm should be monitored for several days.