Prenatal diagnosis of absent right and persistent left superior vena cava

OBJECTIVE: Persistence of left superior vena cava (LSVC) is a known variant of the systemic venous return. In the setting of an otherwise structurally normal heart, absence of the right superior vena cava (RSVC) but persistence of the LSVC is rare. METHODS: We describe the prenatal findings of a fetus with absent right and persistent LSVC. RESULTS: A dichorionic diamniotic twin pregnancy was referred to our centre with cardiac disproportion. Twin A had disproportion at four-chamber level, an absent right but persistent LSVC draining to an enlarged coronary sinus and a hypoplastic transverse aortic arch (<2 mm). Postnatal echocardiography of the asymptomatic baby confirmed the prenatal diagnosis, and serial echocardiograms demonstrated general hypoplasia of the aortic arch but no discrete coarctation (CoA). No intervention was required and the baby is thriving aged 10 months. CONCLUSION: Persistence of LSVC is a known variant of the systemic venous return. In the setting of an otherwise structurally normal heart, absence of the right but persistence of LSVC is rare.