Prenatal diagnosis of absent pulmonary valve syndrome

Abstract

© BMJ Publishing Group Limited 2021. No commercial reuse. See rights and permissions. Published by BMJ. DESCRIPTION An 18yearold woman, with a congenital subaortic interventricular communication, was diagnosed with a 17week gestation. On the first echography, at that gestational age, a subaortic ventricular septal defect (VSD) with an overriding aorta (Ao) was identified (figure 1) associated with bilateral feet polydactyly. A foetal echocardiography, a couple weeks later, confirmed the defects previously mentioned and detected a pulmonary valve (PV) agenesis with a stenotic pulmonary ring, pulmonary free insufficiency and right ventricular (RV) predominance. These features were compatible with absent pulmonary valve syndrome (APVS) with Fallot’s Tetralogy characteristics (TOFtype APVS), a rare cardiac outflow tract abnormality. APVS may be associated with chromosomal anomalies, and this relationship is more frequent with the TOFtype APVS. In the case described, amniocentesis was performed but no chromosomal or genetic variations, namely chromosome 22 microdeletion (22q11.2), were found. Nevertheless, given the poor prognosis, the patient requested pregnancy termination at 23 weeks gestation. The anatomopathological examination was concordant with the ultrasound findings. Despite increasing knowledge, prenatal diagnosis of APVS remains a challenge and a major step in parents counselling given its serious postnatal complications. 6 Globally, it is estimated that, absent PV syndrome affects 0.2%–0.4% of the newborns with congenital heart disease. Moreover, a higher frequency of congenital heart defects is known to occur in the offspring of parents who also have a congenital heart disease, namely atrioventricular defects. Pulmonary artery (PA) dilation on prenatal ultrasound may be a normal variation. However, its identification may also be present in isolated PV stenosis, ductus arteriosus constriction, situations of pulmonary hypertension or in TOFtype APVS. Differentiating features of TOFtype APVS include a massively dilated PA and its branches, left and right (5.8 mm, 6.4 mm and 4.2 mm, respectively, in this case) (figure 2A), a typical pattern of high velocities with colour aliasing between the right ventricle and the PA (figure 2B), a VSD, an overriding Ao and absence of ductus arteriosus. 6 The heart structure can be explored by the first trimester echography but mother characteristics (such as obesity), foetal position or physiological adaptations of the foetal heart inuterus may delay a definite diagnosis. Even an experienced sonographer may raise a suspicion of cardiac abnormalities only on the second or third trimester evaluation. Many times, the diagnosis happens just after birth.