Background: Neonates with critical left heart obstruction and intact or restrictive atrial septum (IAS or RAS) are at risk for hemodynamic instability, hypoxia and acidosis within hours of birth. Accurate prenatal prediction of which neonates will be acutely ill at birth can provide important information for counseling, delivery and resource planning, and guide patient selection for fetal intervention.
Methods: All prenatally diagnosed fetuses with critical left heart obstruction and IAS or RAS from 1/1/2005 through 1/1/2017 were included. Primary outcome was a composite measure of severe neonatal illness defined as arterial pH <7.15, venous pH <7.10, bicarbonate <16, lactic acid >5 or median oxygen saturation <60% within 12 hours of birth. Secondary outcomes were emergent neonatal AS intervention and death/cardiac transplant.
Results: Of the 68 live born fetuses, 52 (79%) had HLHS, and 41 (60%) had a RAS; 36 (52.9%) had severe neonatal illness. Factors associated with severe neonatal illness were IAS, shorter pulmonary vein (PV) anterograde:retrograde (A:R) flow ratio duration, smaller PFO jet width, higher D-wave and A-wave velocities, lower A:R velocity time interval (VTI) ratio, and larger PV diameter. The strongest discriminator for severe neonatal illness was a PV A:R VTI < 2.7 (sensitivity 91%, specificity 97%; p<0.001, AUC 0.94). A risk prediction model using CART analysis with A:R VTI and PV diameter yielded 100% sensitivity and 74% specificity (see image). Predictors for emergent atrial septal intervention (n=37) were similar. Two-year transplant-free survival was 45%. A:R VTI < 2.7 predicted (p=0.03) death or transplant (2 -year rates 63% versus 45% for A:R VTI>2.7).
Conclusions: In neonates with HLHS and IAS or RAS, A:R VTI < 2.7 is highly predictive of severe neonatal illness and need for emergent intervention. This threshold can help guide resource planning and management at delivery and provide criteria for consideration of fetal intervention.