EP09.87: Large thrombus in the left ventricle in a fetus with hypoplastic left heart syndrome

A 33-year-old woman, gravida 3, para 1, was first referred at 21+1 weeks for the second trimester anomaly scan. Antenatal follow-up was complicated by bleeding at 6+3 weeks. Combined first trimester screening test demonstrated low risk for common aneuploideas and PE/FGR and normal heart anatomy. The second trimester anomaly scan showed complex malformation of fetal heart. The fetal echocardiography showed hypoplastic left heart syndrome: right ventricle forms the apex of the heart, left ventricle is rounded with a poor contractility and presence of endocardial fibroelastosis. Large mass in the left ventricle cavity – a thrombus 10,6mm x 5,9mm, no flow in the left ventricle was seen. Aortic valve was hyperechogenic, immobile, no flow; mitral valve hypoplasia, mitral valve stenosis; no interventricular communication; flow across the foramen ovale was from left to right; mitral valve stenosis, mild tricuspid valve regurgitation, ascending aortic hypoplasia, main pulmonary artery dilatation, reversed flow in aortic arch were found. The results of a chromosomal microarray analysis and karyotype of an amniotic fluid sample were normal. The family opted for termination of pregnancy. The autopsy confirms hypoplastic left heart syndrome. The formation in the left ventricle corresponds to a thrombus, on histological examination it consists mainly of erythrocytes. Histological examination of the myocardium reveals a thickened fibrosed endocardium. Conclusions. The large thrombus may appear in the left ventricle due to poor myocardial contractility. Detection of thrombus in the fetal period is rare and rarely has been described in the literature.