Fetal Hypoplastic Left Heart Syndrome

Case of a severe hypoplastic left heart syndrome with mitral and aortic atresia (MA/AA) with retrograde flow in the aortic arch. There is severe aortic valvar annulus hypoplasia with aortic root/ascending aorta hypoplasia and tubular aortic arch hypoplasia. The ductus arteriosus is right to left (PA to Aorta) with retrograde flow in the arch. The foramen ovale is left to right (secondary to mitral atesia). There is left ventricular endocardial fibroelastosis and some degree of mild RV globular dilation. The RV atrio-ventricular valve did not present any clear regurgitation. 

View of the RV dilation and tricuspid valve, as well as the small LV with endocardial fibroelastosis. 

Colour for evaluation of atrio-ventricular regurgitation. There is no clear evidence of tricuspid insufficiency. 

This view outlines the significant aortic annulus hypoplasia, as well as root and ascending aortic hypoplasia. 

Another view by 2D and colour of the RV and significant hypoplastic LV. 

Short axis in 2D with the LV and RV, the RVOT is seen with appropriate caliber of the MPA (which will become the neo-Aorta in the post-natal single ventricular palliation). 

Visualization of the RVOT, Pulmonary valve and MPA. 

In this disease, there is evidence of retrograde Aortic flow necessary to provide blood flow to the coronaries. There is also the presence of a left to right flow through the foramen ovale, which is essential to ensure adequate pulmonary venous drainage. A pulmonary venous doppler may be informative in fetal life about the presence of a restrictive or intact inter-atrial septum (RAS/IAS). RAS/IAS may be an indication for fetal septostomy or immediate post-natal septostomy to alleviate pulmonary venous congestion. Some may develop various degree of pulmonary lymphangiectasia and a fetal MRI may be considered in the context of HLHS-RAS or IAS to evaluate for the presence of "nutmeg" appearance of the fetal lungs - suggestive of underlying lymphangiectasia. 

Case of fetal aortic atresia provided by
Dr Wadi Mawad, Pediatric Cardiologist at the Montreal Children's Hospital

Important articles on potential fetal interventions (aortic valve) in the context of evolving HLHS secondary to fetal aortic valvular obstruction: here and here.

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