EP07.11: Prenatal ultrasound diagnosis of fetal hypoplastic left heart syndrome with left ventricular enlargement: a case report

Hypoplastic left heart syndrome (HLHS) is a congenital cardiac malformation characterised by severe hypoplasia of the left ventricle and left ventricular outflow tract, which occurs in approximately 2 of every 10,000 live births. It usually presents with left ventricular narrowing and aortic atresia with mitral stenosis or atresia. There are fewer reports of HLHS with an enlarged left ventricle. The pregnant woman was 30 years old, G2P0. At 22 weeks of gestation in this singleton pregnancy, we performed ultrasound screening for the second trimester malformations suggesting fetal aortic valve atresia, aortic stenosis with regurgitation, mitral valve atresia, and a markedly enlarged left ventricle, which was considered HLHS. The pregnancy was terminated at our hospital, and subsequently underwent genetic testing with results of heterozygous variants in the NOTCH1 gene (NM_017617.3:c.1955C>A(p.Ser652*), Heterozygote, de novo). This variant, not reported in the literature, can lead to aortic valve disease type 1 (aortic valve disease 1(109730), AD, aortic valve dystrophy, aortic constriction or dilatation, aortic stenosis or aortic valve hypoplasia) and Adams-Oliver syndrome 5 (616028), AD. Autopsy findings were aortic valve atresia, mitral valve widening and thickening, left ventricular enlargement with myocardial infarction, and multiple organ congestion. Combined with the prenatal ultrasound presentation, genetic test results, and pathologic diagnosis, the underlying pathology in this case favoured aortic valvulopathy type 1 (with aortic atresia as the predominant clinical phenotype), resulting in HLHS. The causative gene NOTCH1 is located at 9q34.3, and the mode of pathogenesis is generally autosomal dominant and somatic. The NOTCH1 variant in this case is de novo. Although the risk of recurrence of the de novo variant is low, gonadal chimerism cannot be excluded, and prenatal diagnosis of this variant is required in the next pregnancy.