The “full rectangle” sign: a novel method for ultrasonographic diagnosis of fetal aberrant right subclavian artery

Archives of Gynecology and Obstetrics https://doi.org/10.1007/s00404-024-07785-8 MATERNAL-FETAL MEDICINE The “full rectangle” sign: a novel method for ultrasonographic diagnosis of fetal aberrant right subclavian artery Ettie Piura1,2 · Offra Engel1,2 · Neta Doctory2 · Ofer Markovitch1,2 Received: 13 August 2024 / Accepted: 8 October 2024 © The Author(s) 2024 Abstract Objective To evaluate the feasibility and accuracy of a novel ultrasonographic screening method for an aberrant right subclavian artery (ARSA) using the novel “full rectangle” method. Methods This prospective study was conducted at a tertiary care center, September 2022 to February 2023. The study included unselected pregnant women at 14–38 weeks of gestation referred for routine or targeted anomaly scans. All participants underwent scanning by two experienced sonographers to ascertain the presence or absence of aberrant right subclavian artery (ARSA) using both conventional and novel “full rectangle sign” methods for validation purposes. This is a novel screening method for ARSA that demonstrates the retro-tracheal course at the level of the supra-aortic vessels, forming what we term the “full rectangle sign”. Results A cohort of 138 patients was enrolled. The "full rectangle" sign was discerned in 6 fetuses with ARSA (4.3%), while the typical three-sided figure of the right subclavian artery was demonstrated in the remaining 132 fetuses (95.7%). The novel method demonstrated 100% feasibility and complete concordance with the conventional method. Conclusion The study results indicate that the full rectangle sign serves as an effective and dependable screening tool for identifying ARSA. It offers the advantage of a clear, unobstructed view at a level unaffected by sternum shadowing and eliminates confusion with the azygous vein. Keywords Right subclavian artery · Aberrant right subclavian artery · Prenatal ultrasound What does this study add to the clinical work Routinely examining the three-sided figure vs. the full rectangle sign could enhance prenatal identification of aberrant right subclavian artery. * Ettie Piura 1 Obstetrical & Gynecological Ultrasound Unit, Department of Obstetrics and Gynecology, Meir Medical Center, Kfar Saba, Israel 2 School of Medicine, Faculty of Medical and Health Sciences, Tel Aviv University, Tel Aviv, Israel Introduction The right subclavian artery (RSA) typically originates from the brachiocephalic artery (BCA), the first bifurcation of the aortic arch, and runs toward the right arm. However, in 1–2% of individuals [1, 2], the RSA arises aberrantly from the distal aortic arch as the fourth supra-aortic vessel, taking a retro-tracheal path toward the right arm. This condition, known as aberrant right subclavian artery (ARSA), has been observed in various genetic abnormalities, including Down syndrome [3], and has been associated with cardiac and extracardiac anomalies [4–11]. While ARSA is often asymptomatic, it may cause symptoms that include dysphagia, cough and stridor, resulting from compression of the trachea and esophagus caused by the aberrant anatomy of the aortic arch [12]. This study assessed the feasibility, reproducibility, and accuracy of a novel screening method for ARSA by demonstrating the retro-tracheal course at the level of the supra-aortic vessels, forming what we refer to as the "full rectangle sign”. Vol.:(0123456789) Archives of Gynecology and Obstetrics Materials and methods This prospective, cross-sectional study took place at a tertiary care center from September 2022 to February 2023. The study included pregnant women who were referred for a routine or targeted anomaly scan. Two sonographers, O.M. and E.P., with 20 and 9 years of scanning experience, respectively, performed the scans. The primary objective was to determine the presence or absence of ARSA using two methods: the conventional method described by Chaoui et al., which is considered the “gold standard” as it has been validated in multiple studies and the novel "full rectangle" method. Intra-observer agreement and reproducibility of the diagnosis was evaluated by having the same sonographer assess the full rectangle twice during the scan. The inter-observer assessment was performed in a separate study that included 30 unselected patients who were scanned by two investigators (O.M and E.P.) in a blinded fashion. None of the patients were found to have a fetus with ARSA, using both methods. Both sonographers also reviewed the video clips of each ARSA case. There was full agreement between investigators. Furthermore, to ensure quality control and validation, the data analysis included only patients who were subsequently referred for echocardiography due to appropriate indications, such as pregestational maternal diabetes, cardiac or cardiac-associated fetal abnormalities, maternal administration of medication with teratogenic cardiac effects, and first-degree relative of the fetus with a congenital cardiac abnormality. A pediatric cardiologist examined and corroborated all ARSA and non-ARSA cases. In the conventional approach, RSA visualization involves angling the transducer toward the right shoulder in an axial section at the three-vessel view level, to depict its position in the upper plane of the transverse aortic arch. When a fetus has an ARSA, it appears lower in the thorax compared to the typical right subclavian artery. In the three-vessel tracheal view, it manifests as a vessel coursing behind the trachea toward the right arm. The full rectangle sign involves visualizing the aortic arch and supra-aortic vessels at the level of the fetal shoulders. Ideally, the fetus should be in a supine position. To demonstrate the full rectangle sign, the standard three-vessel trachea view must be obtained first. This view, described previously by Yagel et al., is achieved in an axial view of the chest and demonstrates the pulmonary artery, aorta, and the superior vena cava [13]. To visualize the supra-aortic vessels, the ultrasound transducer is then moved cranially to the fetal neck at the level of the shoulders. Understanding the spatial arrangement of the aortic arch and its branches in relation to neighboring structures greatly facilitates visualization of the three-sided figure and the full rectangle sign. A cross-sectional view at this level reveals the ascending aorta on the right side, the left brachiocephalic vein taking a horizontal course, and the initial segment of the descending aorta on the left side, outlining a three-sided figure. The ascending aorta stems from the left ventricle, located anteriorly and slightly to the right of the trachea. Moving across the midline, the aortic arch passes in front of the trachea and over the left main bronchus, proceeding toward the left side of the trachea. From this juncture, it descends alongside the thoracic esophagus. The fetal trachea displays a distinct ultrasound appearance, characterized by bright echogenic walls encl (...truncated)