• vascular ring
• right aortic arch
• prenatal diagnosis
• fetus
• arterial duct

Aim: to study the different characteristics of arterial duct (AD) in a series of right aortic arch (RAA) prenatally detected.
Method: among 832 congenital heart diseases (CHD), referred to a tertiary center between 2005-2019, 98 cases of RAA were identified. Based on location, body planes alignment, and relationship with the trachea, we classified the AD in 7 types: 1) left-sided, transverse; 2) left-sided, vertical; 3) from the undersurface of AA, vertical; 4) right-sided, mirror-image “V”, transverse; 5) right-sided, “H” shaped, transverse; 6) bilateral; 7) absent or unidentifiable. Type 1 cases were further distinguished in: a) with aberrant subclavian artery (ALSA), b) mirror-image branching and c) double aortic arch (DAA).
Result: type 1 was the largest group (42/98), 4 cases had CHD, none pulmonary outflow obstruction (POO). Symptoms were present in 12/29 of cases. Proximal stenosis of ALSA was detected in 26% of type 1a cases. Prenatal misclassification between mirror-image branching and DAA with atretic segment was common. Type 2, type 3 and type 7 AD were associated with tetralogy of Fallot (TOF) or equivalents. In type 5 associated with CHD, none had POO; in isolated, 3 had asymptomatic hypoplasia of left pulmonary artery (LPA). Two cases with type 6 AD had disconnection of LPA.
Conclusion: in RAA, symptomatic vascular rings were limited to type 1 AD. POO is always present when the AD lies on a vertical plane or is absent but not when on the transverse plane. Bilateral AD is rare and entails the risk of functionary loss of the left lung after birth.