Prenatal echocardiographic assessment of right aortic arch

Objectives To report our experience with fetal diagnosis of right aortic arch (RAA) variants based on the ductus arteriosus (DA) anatomy and brachiocephalic vessel branching pattern in relation to the trachea, and to establish whether the echocardiographic 'V-shaped' or 'U-shaped' appearance of the junction between the DA and aortic arch (AA) in the fetal upper mediastinal view is sufficiently accurate for assessment of fetal AA anatomy. Methods This was a retrospective study of pregnancies with a prenatal diagnosis of fetal RAA that had postnatal confirmation of AA anatomy, referred to our tertiary center during 2011-2017. Prenatal and postnatal medical records, including echocardiographic and computed tomography (CT)/magnetic resonance imaging (MRI) scan reports, were reviewed, and cardiac and extracardiac abnormalities and the results of genetic testing were recorded. Results Of 55 consecutive pregnancies with a prenatal diagnosis of fetal RAA, six were lost to follow-up, one was terminated and three were excluded due to lack of postnatal confirmation of AA anatomy. Of the remaining 45 pregnancies, AA anatomy was assessed postnatally by CT in 39, by MRI in one and by direct examination at cardiac surgery in five. A U-shaped appearance was found in 37/45 (82.2%) patients, all of which had a complete vascular ring (CVR). Of these 37 patients, on postnatal confirmation, 21 (56.8%) had RAA with Kommerell's diverticulum, left posterior ductus arteriosus (LPDA) and aberrant left subclavian artery (ALSA) (RAA/LPDA/ALSA), 11 (29.7%) had a double AA (DAA), four (10.8%) had RAA with Kommerell's diverticulum, LPDA and mirror-image (MI) branching (RAA/LPDA/MI), and one (2.7%) had RAA with Kommerell's diverticulum, LPDA and aberrant left innominate artery (ALIA) (RAA/LPDA/ALIA). A V-shaped appearance was found in 3/45 (6.7%) patients, all of which had RAA with right DA not forming a CVR and MI branching. In the 5/45 (11.1%) fetuses with neither U- nor V-shaped appearance, RAA with left anterior DA arising from the left innominate artery and MI branching, not forming a CVR, was found. Twelve (26.7%) fetuses had a congenital heart defect (CHD). RAA forming a CVR (U-shaped appearance) was associated with a septal defect in 6/37 (16.2%) fetuses, while RAA not forming a CVR (V-shaped appearance or no U- or V-shaped appearance) was associated with major CHD in 6/8 (75.0%) fetuses. Conclusions In fetuses with RAA, V-shaped appearance of the junction between the DA and AA indicates only that the transverse AA and DA run together on the same side of the thorax (trachea) while a U-shaped appearance is always a sign of a CVR. Among fetuses with a CVR, RAA/LPDA/MI is more frequent than described previously. Finally, RAA forming a CVR is not usually associated with complex CHD, as opposed to RAA not forming a CVR. Copyright (c) 2018 ISUOG. Published by John Wiley & Sons Ltd