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

## TL;DR

This study examines fetal heart syndrome with a specific heart defect and finds that a certain heart structure pattern and a lung condition are linked, with treatment showing some improvement.

## Contribution

The study identifies four distinct atrial septal morphology patterns in fetuses with HLHS and RAS, and shows that VTI ratio correlates with PL improvement after intervention.

## Key findings

- Most fetuses with HLHS and RAS had a hypoplastic left atrium.
- Pulmonary venous VTI ratio correlated with PL on fetal lung MRI and improved with fetal atrial septal intervention.

## Abstract

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.

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.

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.

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.

What's already known about the topic?◦Hypoplastic left heart syndrome with restrictive or intact atrial septum has high mortality, partly due to in utero development of pulmonary lymphangiectasia.◦Fetal atrial septal invention may modify the high mortality risk; however, patient selection is challenging owing to highly heterogeneous but poorly characterized atrial septal morphology.What does this study add?◦We identified four different atrial septal morphology patterns in fetuses with hypoplastic left heart syndrome and variants with restrictive or intact atrial septum. Contrary to a prior study, we found that most fetuses had a hypoplastic left atrium.◦Pulmonary venous VTI ratio correlated with pulmonary lymphangiectasia on fetal lung MRI, and most improved with fetal atrial septal intervention.

What's already known about the topic?

Hypoplastic left heart syndrome with restrictive or intact atrial septum has high mortality, partly due to in utero development of pulmonary lymphangiectasia.

Fetal atrial septal invention may modify the high mortality risk; however, patient selection is challenging owing to highly heterogeneous but poorly characterized atrial septal morphology.

What does this study add?

We identified four different atrial septal morphology patterns in fetuses with hypoplastic left heart syndrome and variants with restrictive or intact atrial septum. Contrary to a prior study, we found that most fetuses had a hypoplastic left atrium.

Pulmonary venous VTI ratio correlated with pulmonary lymphangiectasia on fetal lung MRI, and most improved with fetal atrial septal intervention.