![]() During embryogenesis ( top drawing), a double aortic arch exists, made by the left and right aortic arches, which forms a complete vascular ring surrounding the trachea and esophagus. The left ductus arteriosus persists, whereas the right ductus arteriosus regresses.įigure 29.1: Schematic drawings of various forms of aortic arch abnormalities. The course of the right subclavian artery is posterior to the esophagus and trachea toward the right arm. This leads to the presence of a left-sided aortic arch with the following arising vessels: the right common carotid artery as the first branch, the left common carotid artery as the second branch, the left subclavian artery as the third branch, and an aberrant right subclavian artery (ARSA) as the last branch ( Fig. This anomaly results from partial regression of the right aortic arch between the origin of the right common carotid artery and the right subclavian artery ( Fig. The left ductus arteriosus persists, whereas the right ductus arteriosus regresses.ī: Left-Sided Aortic Arch with Aberrant Right Subclavian Artery The right subclavian and right common carotid arteries merge to form the right brachiocephalic (or innominate) artery. The regression of the right aortic arch segment distal to the origin of the right subclavian artery results in a left aortic arch (normal anatomy) ( Fig. Common aortic arch abnormalities encountered on prenatal ultrasound are discussed in this chapter.Įmbryologic events that result in various anatomic orientations of the aortic arch and its branches are hereby presented. Normal and abnormal development of the aortic arch branching is thus related to which site of the left or right aortic arch regresses or persists during embryonic development ( 2, 3). In addition, the left and right pulmonary arteries are connected to the left and right aortic arches, respectively, by a left and right ductus arteriosus in the region of the subclavian arteries ( Fig. The left and right aortic arches give rise to two vessels each: the left and right common carotid and subclavian arteries, respectively ( Fig. The left and right aortic arches thus form a complete vascular ring, surrounding the trachea and esophagus. This theory is based on the presence of double aortic arch in the embryo, where the ascending aorta splits into a right and a left aortic arch, which merge to form the descending aorta, anatomically located in a central position, anterior to the spine ( Fig. The hypothetical double aortic arch theory, suggested by Edwards ( 1), provides an explanation for various aortic arch abnormalities ( 2, 3). It is generally acknowledged that anomalies of aortic arch branching are best understood when basic embryology of the aortic arch is reviewed. ![]()
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