Echocardiographic predictors of neonatal illness severity in fetuses with critical left heart obstruction with intact or restrictive atrial septum.

Background: Neonates with critical left heart obstruction and intact atrial septum (IAS) or restrictive atrial septum (RAS) are at risk for hypoxia within hours of birth and remain a group at high risk for mortality.

Methods: Prenatally diagnosed fetuses with critical left heart obstruction and IAS or RAS with follow-up from January 1, 2005, to February 14, 2017, were included. Primary outcome was a composite measure of severe neonatal illness (pH < 7.15, venous pH < 7.10, bicarbonate < 16 mmol/L, lactic acid > 5 mmol/L, or median oxygen saturation < 60% within 2 hours of birth).

Results: Of 68 live born fetuses, 52 (76.5%) had hypoplastic left heart syndrome, 14 (20.5%) had critical aortic stenosis, and two (3%) had complex anatomy with mitral stenosis/atresia. There were 27 (39.7%) fetuses with IAS and 41 (60.3%) with RAS. Severe neonatal illness was present in 36 (52.9%). The strongest discriminators for severe neonatal illness were a pulmonary vein A:R VTI ≤ 2.7 (P < 0.001, AUC 0.93) and larger pulmonary vein diameter (P = 0.025, AUC 0.77). A:R VTI ≤ 2.7 predicted death or transplant (log-rank P = 0.03).

Conclusions: In neonates with hypoplastic left heart syndrome and IAS or RAS, A:R VTI ≤ 2.7 is predictive of severe neonatal instability. This threshold can help guide resource planning, delivery management, and improve fetal intervention criteria.