VP22.22: Prenatal diagnosis of Shone's syndrome: ultrasonographic findings and parental counselling

Shone's syndrome (SS) is a rare congenital heart disease (CHD) characterised by four defects: supravalve mitral membrane, parachute mitral valve, subaortic stenosis and aortic coarctation. Incomplete forms of SS are more common and consist in the coexistence of only two or three of these left heart obstructive anomalies. To date there is limited data on prenatal diagnosis of this CHD. We report an incomplete SS diagnosed prenatally and discuss its parental counselling. A 44-year-old, G3P2, healthy woman was referred to our Fetal Medicine Department at 21 weeks of gestation with ultrasound features of CHD. There was no family history of cardiac defects and the first trimester screening for chromosomal abnormalities and major defects was normal. Fetal echocardiography identified mitral and aortic valves stenosis, with turbulent anterograde flow, subaortic interventricular communication with bidirectional flow, hypoplastic ascending aorta and aortic arch with retrograde flow to its distal portion, dilatation of right atrial and ventricle and hypoplastic left ventricle. No extracardiac anomalies were observed. There were no abnormal findings in karyotype and microarray analysis of the amniotic fluid. After a multidisciplinary evaluation, parents were informed about the clinical prognosis and opted for termination of pregnancy. Anatomopathological study corroborated the ultrasound findings. A congenital mitral valve obstruction is the main pathological event that leads to the maldevelopment of left heart outflow tract. The degree of this underdevelopment will influence clinical presentation at birth, need for medical/surgical intervention and morbimortality. In this case, prenatal echocardiography revealed features compatible with incomplete SS that was progressing to a hypoplastic left heart syndrome. These findings were crucial to provide parents the proper counseling, including implications underlying this pathology and therapeutic options.