Fetal Diagnosis of Hypoplastic Left Heart Syndrome With Restrictive Atrial Septum—Atrial Septal Morphology, Associated Lung Disease and Outcomes

Objective: Fetuses with hypoplastic left heart syndrome (HLHS) and restrictive/intact atrial septum (RAS) have high mortality, partly due to pulmonary lymphangiectasia (PL). This study aimed to characterize atrial septal morphology in fetuses with HLHS and RAS and evaluate the impact of fetal intervention on PL and outcomes. Method: We retrospectively reviewed clinical data, fetal echocardiograms, and MRIs from all fetuses with HLHS/HLHS-variants and RAS over 20 years. RAS was defined as pulmonary venous forward-to-reverse VTI ratio ≤ 5:1. Results: We identified 54 fetuses (gestational age of 24.2 weeks; 21.2–28.1) with HLHS (81%) or HLHS variant (19%) and RAS. Most had a hypoplastic left atrium (LA, 80%). Four atrial septal morphology patterns were identified. PL was present among all patterns and associated with lower VTI ratio (p = 0.046). Mean VTI ratio improved in fetuses who underwent atrial septal intervention (n = 12), compared to those without (p = 0.001). Among five fetuses with pre-intervention PL and serial MRIs, three improved. Seventeen neonates were live-born with intention-to-treat; 6-months mortality was 38% with no difference by morphology pattern, PL, or fetal intervention. Conclusion: Most fetuses with HLHS and RAS had hypoplastic LA. VTI ratio correlated with PL on fetal lung MRI, and most improved with fetal atrial septal intervention.