Four‐Dimensional Power Doppler Sonography With the HDlive Silhouette Mode in Antenatal Diagnosis of a Right Aortic Arch With an Aberrant Left Subclavian Artery

Aortic arch anomalies develop as a result of abnormal regression of one of the pharyngeal arches, resulting in abnormalities in the aortic arch position or branching pattern.1 They may present alone or associated with other congenital heart defects. The most common type is the right aortic arch (RAA), with an estimated incidence of approximately 0.1%. 2 An association of a right aortic arch with 22q11 microdeletion has been reported.1,3 There have been numerous reports on the antenatal diagnosis of a right aortic arch with an aberrant left subclavian artery using 2dimensional (2D) echocardiography, 2D color Doppler sonography, and 3-dimensional (3D) power Doppler sonography.1,2,4–6 However, to the best of our knowledge, the use of 4-dimensional (4D) power Doppler sonography with the HDlive silhouette mode (GE Healthcare Japan, Tokyo, Japan) for the antenatal diagnosis of a right aortic arch with an aberrant left subclavian artery has not been reported previously. A 37-year-old primigravida was referred to our ultrasound clinic at 29 weeks’ gestation because of a suspected right-sided descending arch. Two-dimensional sonography (Voluson E8; GE Healthcare Japan) showed a single living fetus with biometric measurements consistent with gestational age. Two-dimensional fetal echocardiography showed an abnormal 3-vessel and trachea view, and the aortic arch was present on the right side of the trachea, with the ductus arteriosus on the left side of the trachea, connected by a vascular segment behind the trachea (diverticulum of Kommerell). An aberrant left subclavian artery originating from the diverticulum of Kommerell was suspected. There was no other fetal abnormality. At 34 weeks, 2D power Doppler sonography with a 3vessel and trachea view (Voluson E10) showed the pulmonary artery, right aortic arch, superior vena cava, and a vascular ring around the trachea. Also, the azygos vein and right pulmonary vessels were visualized (Figure 1A). Fourdimensional power Doppler sonography with the HDlive silhouette mode clearly showed the vascular ring around the trachea at the level of the upper mediastinum in addition to the spatial 3-vessel view (Figure 1B and Video 1). The descending aorta was noted on the right anterior side of the spine. An aberrant left subclavian artery originating from the diverticulum of Kommerell was clearly identified (Figure 1C and Video 2). A diagnosis of a right aortic arch with an aberrant left subclavian artery was made. At 41 weeks’ gestation, a cesarean delivery was performed because of rupture of membranes while the head was unengaged, resulting in a male neonate weighing 4054 g with a height of 51 cm. The Apgar scores were 8 at 1 minute and 9 at 5 minutes, and the umbilical artery pH was 7.301. Neonatal echocardiography confirmed the diagnosis of a right aortic arch with an aberrant left subclavian artery. The diagnosis of aortic arch anomalies is a challenging task for obstetricians. The axial view of the upper mediastinum (namely, 3-vessel and trachea view) is an approach to evaluating the aortic arch by visualizing the V-shaped configuration formed by the junction of the aortic and ductal arches, with the trachea present posteriorly under normal conditions.2 However, detailed and precise detection of the branching pattern is mandatory to differentiate a right aortic arch from other aortic arch anomalies.7 Aortic arch anomalies have also been reported to be closely associated with genetic disorders and multiple congenital cardiac anomalies; therefore, accurate identification of the anatomic changes is needed for improved postnatal management. In this case, 2D echocardiography showed the loss of the V-shaped confluence of the 3-vessel and trachea view. Two-dimensional power Doppler sonography was beneficial, as it showed the vascular ring around the trachea formed by the ductus arteriosus, descending aorta, diverticulum of Kommerell, and right aortic arch. Fourdimensional power Doppler sonography with the HDlive silhouette mode facilitated a spatial 3-vessel view, which showed the relationship and size comparison among them. Therefore, 3D reconstruction of a typical vascular ring was clearly shown. Moreover, an aberrant left subclavian artery was clearly shown, as well as the azygos vein and right pulmonary vessels. The key point is that the relationship of these vessels with the spine could be understood because the spine can be seen by using the HDlive silhouette mode. The descending aorta was noted on the right anterior side of the spine. This finding is another important diagnostic clue in cases of a right aortic arch,1 which cannot be obtained with conventional 3D power Doppler sonography. Therefore, accurate localization and description of the branching patterns of great arteries and an improved understanding of the spatial relationship are easily possible. Fourdimensional power Doppler sonography with the HDlive silhouette mode combines the advantages of a spatial view of great vessels in addition to visualization of the spine as a landmark. Its use may provide potential advantages in the