The aortic arch normally gives rise to three major branches in left-to-right sequence:
Variants and anomalies can arise from deviations in embryological development of the aortic arches (particularly the 3rd, 4th, and 6th pharyngeal arches). These can be asymptomatic, cause vascular rings, or be associated with congenital heart disease.
Normal aortic arch development:
Embryologic development of the thoracic aorta and its branches. (A)—The scheme highlights the development of the six arches from the aortic sac during the 5th week of development, the 1st and 2nd arches have regressed (dashed line). The truncus arteriosus is partially divided by the conotruncal septum. (B)—Aortic arches at 7 weeks of development. The segments of the dorsal aorta connecting the third and fourth arch arteries disappear, as well as the fifth, part of the right and sixth arches and a portion of the right dorsal aorta. (C)—At 8 weeks, the thoracic aorta and the epiaortic vessels have almost completed their development. Note the patency of the ductus arteriosus, originating from the left sixth aortic arch.
di Gioia CRT, Ascione A, Carletti R, Giordano C. Thoracic Aorta: Anatomy and Pathology. Diagnostics. 2023; 13(13):2166. https://doi.org/10.3390/diagnostics13132166
Edward’s conceptual model of aortic arch anomliaies:
Schemes of the embryonic development of the aortic arch. Schematic depicting a hypothetical DAA model introduced by Edwards, which illustrates that two aortic arches, right and left, connect the ascending and descending aortas. If the situation persists without regression of either side of arch, the DAA is formed (A). In normal development, the LAA and left ductus persist, and the RAA distal to the origin of the right subclavian artery (RSA) and the right ductus regress (B). If the regression presents between the origins of the right common carotid artery (RCCA) and the RSA on the RAA, the RSA can only connect with the descending aorta, forming an ARSA (C). On the other hand, if the left arch regresses while the right arch is conserved, then the RAA is formed. If the regression presents between the origins of the left common carotid artery (LCCA) and the left subclavian artery (LSA) on the LAA, the LSA can only connect with descending aorta, which is the ALSA (D). The proximal part of the ALSA carries blood from the ductus into the descending aorta, and it is wide in dimension. The dilated proximal part of the ALSA is called the aortic KD. If the disruption of the LAA occurs distal to the origin of the LSA, an RAA with MIB is formed (E).
EDWARDS JE. Vascular rings related to anomalies of the aortic arches. Mod Concepts Cardiovasc Dis. 1948;17(8):1. Wang Y, Fan M, Siddiqui FA, et al. Strategies for accurate diagnosis of fetal aortic arch anomalies: benefits of Three-Dimensional sonography with spatiotemporal image correlation and a novel algorithm for volume analysis. Journal of the American Society of Echocardiography. 2018;31(11):1238-1251. doi:10.1016/j.echo.2018.07.010
Classification of aortic arch variants and anomalies based on arch-sidedness and mirror imaging ALSA: aberrant left subclavian artery, ARSA: aberrant right subclavian artery, LAA: left-sided aortic arch, LSA: left subclavian artery, RAA: right-sided aortic arch, RSA: right subclavian artery.
Bae SB, Kang EJ, Choo KS, et al. Aortic Arch Variants and Anomalies: Embryology, Imaging Findings, and Clinical Considerations. Journal of Cardiovascular Imaging. 2022;30(4):231. doi:https://doi.org/10.4250/jcvi.2022.0058
Common aortic arch variants:
| Variant/anomaly | Description | Clinical relevance |
|---|---|---|
| ‣ | Common origin of BCT and LCCA | None; common variant |
| ‣ | Arises distal to LSA; posterior to esophagus | Dysphagia lusoria, aneurysm risk |
| ‣ | Aortic arch to right of trachea | May form vascular ring, associated with CHD |
| ‣ | Two arches encircle trachea/esophagus | Severe airway symptoms in infants |
| ‣ | Discontinuity between arch and descending aorta | Critical neonatal condition; needs surgery |
| ‣ | Direct aortic origin between LCCA & LSA | Important f |
Associated Structures & Anomalies
| Structure | Associated Variant |
|---|---|
| ‣ | Focal dilatation at origin of aberrant subclavian artery |
| Ligamentum Arteriosum | Can complete a vascular ring |
| ‣ | Remnant of ductus arteriosus (seen in infants) |