Prediction and perinatal management of severely restrictive atrial septum in fetuses with critical left heart obstruction: clinical experience using pulmonary venous Doppler analysis.

OBJECTIVE: Up to 20% of fetuses with critical left heart obstructive lesions have highly restrictive or intact atrial septae. Although this condition is generally tolerated in utero, severe hypoxemia requiring emergency atrial septostomy often develops in newborns with restrictive atrial septum. We have reported that a pulmonary venous Doppler forward/reverse time-velocity integral ratio less than 5 is highly predictive of the need for emergency atrial septostomy. We reviewed our subsequent experience using fetal pulmonary venous Doppler patterns to identify and manage fetuses with critical left heart obstruction and suspected restrictive atrial septum.

METHODS: A retrospective review of neonates with a prenatal diagnosis of critical left heart obstruction was performed. Fetal restrictive atrial septum was defined as a small/absent interatrial shunt on 2-dimensional imaging and a mean forward/reverse time-velocity integral ratio of 5 or less. Available serial pulmonary venous Doppler data were reviewed. The primary outcome was postnatal confirmation of restrictive atrial septum or severe left atrial hypertension.

RESULTS: Eight of 39 infants had a forward/reverse time-velocity integral ratio of 5 or less. A restrictive atrial septum was confirmed postnatally in 6 of 8 infants. Overall, a forward/reverse time-velocity integral ratio of 5 or less had a sensitivity of 100% and specificity of 94% for emergency atrial septostomy. Lowering the cutoff value to 3 or less would have eliminated false-positive diagnoses in the current series. Serial data demonstrated that late second trimester values did not change in later gestation with respect to either threshold in 30 of 32 fetuses.

CONCLUSIONS: In the fetus with critical left heart obstruction, a threshold forward/reverse time-velocity integral ratio of 3 or less optimizes specificity for predicting emergency atrial septostomy. Most late second trimester values will not change over time with regard to threshold levels.