Methods
Twenty-two fetuses with DAA, 8 cases of which with hypoplastic left arch and 2 cases of which with very hypoplasia of the distal left arch, and 65 fetuses with RAA-MB prenatally diagnosed with post-natal or autopsy findings confirmed from our database of 27652 fetuses were analyzed retrospectively in our center from October 2015 to October 2019. Clinical data and prenatal echocardiographic features of the DAA and RAA-MB were collected. The study design was approved by the ethics review board of our hospital. Fetal autopsy following the termination of the pregnancy was performed with the consent of the parents. Informed consent was unnecessary for the other cases, as this is a retrospective study.
Inclusion criteria: the cases confirmed by postnatal or autopsy findings, clear three-vessel-trachea view, and a visible color in the Doppler image of the first branch of the right aortic arch. Exclusion criteria: the angle of the first branch of the RAA cannot be measured due to the invisible beginning part of the first branch of the RAA.
All the fetal echocardiographic examinations were performed by a physician with over 5 years of experience in our maternal-fetal medicine consultation center, based on the guidelines previously published.5-7 All fetal echocardiographs were obtained using a Voluson E8/E10 equipped with a 2D/3D probe of 2- to 8-MHz (GE Healthcare, Zipf, Austria).
The angle between the right aortic arch and its first branch was measured by color Doppler imaging (Figure. 1) on the 3VT view. In the DAA, the angle between the proximal parts of the two arches was measured, while in the RAA-MB, the angle between the RAA and the left brachiocephalic artery was measured.
Two observers completed the measurements of angles of the DAA and RAA with mirror branches. They were blinded to the final results. Twenty cases were randomly selected to measure the angle to determine the internal and interval variability of the observers by using the same view. The interval between the two measurements for the same observer was two weeks.