- Email: [email protected]
Right aortic arch and its variants
Journal of Cardiovascular Computed Tomography (2010) 4, 293–300
Pictorial Essay
Right aortic arch and its variants Jeffrey P. Kanne, MDa,*, J. David Godwin, MDb a
Department of Radiology, University of Wisconsin School of Medicine and Public Health, MC 3252, 600 Highland Avenue, Madison, WI 53572-3252, USA and bDepartment of Radiology, University of Washington Medical Center, Seattle, WA, USA KEYWORDS: Aorta; Congenital; Right aortic arch; Double aortic arch; Computed tomography
Abstract. A number of congenital anomalies of the aortic arch complex can occur, ranging from asymptomatic normal variations in arch vessel branch pattern to symptomatic vascular rings, stenoses, and arch interruptions with a frequency ranging from 0.5% to 3.0%. A right aortic arch is present in 0.1% of the population and can occur in isolation or be associated with congenital heart disease. Patients may present at any age with signs and symptoms of airway or esophageal compression, heart failure, or abnormal chest imaging studies. This pictorial essay will show the computed tomography and appearances of congenital variations of the right aortic arch and use Edwards’ hypothetical embryonic double aortic arch model to explain the cause of some of these variants. Ó 2010 Society of Cardiovascular Computed Tomography. All rights reserved.
Introduction Congenital anomalies of the aortic arch complex range from asymptomatic normal variations in arch vessel branch pattern to symptomatic vascular rings, stenoses, and arch interruptions.1 The frequency of aortic arch anomalies ranges from 0.5% to 3.0%.2 Patients can present at any age with an abnormal chest radiograph or a variety of signs and symptoms, including dysphagia, dyspnea, hypertension, and congestive heart failure. A right aortic arch occurs in approximately 0.1% of adults.3,4 It may be an incidental finding but can be associated with congenital heart disease. Congenital right aortic arch anomalies are sometimes recognizable on chest radiographs, Conflict of interest: Jeffrey P. Kanne is a consultant for superDimension, Inc (not relevant to content of manuscript) and for PTC Therapeutics Inc (not relevant to content of manuscript). Dr Godwin reports no conflicts of interest. * Corresponding author. E-mail address: [email protected] Submitted January 11, 2010. Accepted for publication July 8, 2010.
but computed tomography (CT) and magnetic resonance imaging (MRI) more clearly show anomalies and are thus often definitive.5,6 In 1948, Edwards proposed a system that used a hypothetical embryonic double aortic arch to explain the various congenital anomalies of the aortic arch determined by the site of interruption or atresia of the embryonic arch system (Fig. 1).7 From this model, one can gain an understanding of the embryogenesis of a right aortic arch and some of its variants. This pictorial essay reviews the CT appearances of many congenital variations of the right aortic arch (Table 1) and use Edwards’ embryonic double arch model to show the embryogenesis of some of these anomalies. Anomalies are discussed in decreasing frequency as they are encountered in the adult.
Embryology The aorta and its branches develop early in embryogenesis.8 During the fourth week of embryogenesis the
1934-5925/$ - see front matter Ó 2010 Society of Cardiovascular Computed Tomography. All rights reserved. doi:10.1016/j.jcct.2010.07.002
294
Journal of Cardiovascular Computed Tomography, Vol 4, No 5, September/October 2010 arches have no known derivatives. The proximal segment of the left sixth embryonic aortic arch becomes the left pulmonary artery, and its distal segment becomes the ductus arteriosus. The proximal segment of the right sixth embryonic aortic arch becomes the right pulmonary artery, and the distal segment involutes. Failure of normal development, segmentation, or regression of these embryonic aortic arches leads to the multiple aortic arch anomalies that have been described. Some aortic arch anomalies occur in isolation, whereas others are frequently associated with congenital heart disease.
Right aortic arch Figure 1 Schematic based on Edwards’ hypothetical embryonic double aortic arch. AA, ascending aorta; DA, descending aorta; R SCA, right subclavian artery; R CCA, right common carotid artery; L CCA, left common carotid artery; L SCA, left subclavian artery; PA, pulmonary artery; ducti arteriosi (arrows).
branchial (pharyngeal) arches form, and their arterial supply comes from the heart. These 6 paired arteries arise from the aortic sac and terminate in the ipsilateral dorsal aorta, forming embryonic aortic arches. The aortic arches do not all exist at the same time, with some already gone when others appear. The primitive pattern of embryonic aortic arches takes on the adult pattern during the sixth through eighth weeks of embryogenesis. The first and second paired embryonic aortic arches regress. The third paired embryonic aortic arches form the common carotid arteries, and their distal segments form the internal carotid arteries in conjunction with the dorsal aortae. Normally, the left fourth embryonic aortic arch forms a portion of the adult aortic arch, and the right fourth embryonic aortic arch forms the right subclavian artery. However, an adult right aortic arch forms when this pattern is reversed. The paired fifth embryonic aortic
Table 1
The most common form of right aortic arch in adults is associated with an aberrant left subclavian artery (Figs. 2 and 3),9 which originates as the last arch vessel and crosses the mediastinum from right to left posterior to the esophagus. The incidence of associated congenital heart disease is low, with most patients having tetralogy of Fallot.4 Sometimes the origin of the aberrant left subclavian artery has a bulb-like dilation called the diverticulum of Kommerell, which develops from the remnant of the embryonic left fourth aortic arch. A diverticulum of Kommerell implies a left ligamentum arteriosum is present, forming a vascular ring. However, most patients with this configuration are usually asymptomatic, indicating the vascular ring is quite loose. A diverticulum of Kommerell, particularly when large, can indent the posterior wall of the esophagus and trachea, resulting in symptoms.
Mirror-image branching Mirror-image branching of the arch vessels is the most common form of right aortic arch and is associated with
Right aortic arch anomalies
Anomaly
Descending aorta
Subclavian artery
R R R R R
Right Right Right Left Right
Normal Normal Aberrant Aberrant Aberrant brachiocephalic Isolated left Normal
arch, arch, arch, arch, arch,
Aberrant left subclavian artery
mirror image branching circumflex ligamentum aberrant L subclavian aberrant L subclavian aberrant brachiocephalic
R arch, isolated L subclavian Double arch
Right Left . right
CHD, congenital heart disease; L, left; R, right. Adapted from VanDyke and White.15
Ductus
Frequency
Vascular ring
Associated CHD
Usually left Left descending Left Left Unknown
Common Rare Common Rare Rare
No Yes Yes Yes Possible
Almost always No Uncommon Yes Unknown
Left, usually patent Usually left
Rare Common
Possible Yes
Yes Rare
Kanne and Godwin
Right aortic arch and its variants
295 congenital heart disease, nearly always cyanotic, in approximately 98% of patients (Figs. 4 and 5). Most patients with this pattern of right aortic arch present in childhood. Approximately 25% of patients with tetralogy of Fallot and 25%–50% of patients with truncus arteriosus have right aortic arch with mirror-image branching. A rare variant of this anomaly forms a vascular ring with a retroesophageal aortic diverticulum connecting to the left ductus arteriosus (Figs. 6 and 7).10 Because of the extremely high association with cyanotic congenital heart disease, cardiac morphology is almost always abnormal on imaging studies. Comprehensive evaluation relies on echocardiography, CT, MRI, or a combination.
Right aortic arch with left descending aorta Figure 2 Schematic based on Edwards’ hypothetical embryonic double aortic arch system shows a right aortic arch with aberrant left subclavian artery. AA, ascending aorta; DA, descending aorta; R SCA, right subclavian artery; R CCA, right common carotid artery; L CCA, left common carotid artery; L SCA, left subclavian artery; PA, pulmonary artery.
An uncommon variant of right aortic arch, sometimes referred to as a circumflex aorta or retroesophageal aortic segment,4 is one in which the transverse arch courses posterior to the esophagus and continues as a left descending aorta (Fig. 8). This anomaly may be a variant of double aortic arch
Figure 3 (A) Contrast-enhanced CT image shows a right aortic arch (thin arrow) with an aberrant left subclavian artery (arrowhead). Left brachiocephalic artery (wide arrow). (B) Contrast-enhanced CT image more caudad shows the descending aorta on the right (arrow) and a small persistent left superior vena cava (arrowhead). (C) Coronal maximum-intensity projection shows the aberrant left subclavian artery (thin arrow) arising from a large retroesophageal diverticulum of Kommerell (*). The right common carotid (arrowhead) and subclavian arteries (wide arrow) arise normal. The descending aorta (curved arrow) travels back to the right as it descends.
296
Journal of Cardiovascular Computed Tomography, Vol 4, No 5, September/October 2010 the population.4,14 In infants, it usually presents with stridor or difficulty in feeding. However, patients with this anomaly can remain asymptomatic or present later in life. There is no increased incidence of congenital heart disease with double aortic arch. On CT, the right arch is larger, posterior, and more cephalad than the left arch in about two-thirds of patients,
Figure 4 Schematic based on Edwards’ hypothetical embryonic double aortic arch system shows right aortic arch with mirror image branching. AA, ascending aorta; DA, descending aorta; R SCA, right subclavian artery; R CCA, right common carotid artery; L CCA, left common carotid artery; L SCA, left subclavian artery; PA, pulmonary artery; left ductus arteriosus (arrow).
with focal left arch atresia. A symptomatic vascular ring is formed in the setting of an aberrant left subclavian artery and a left ligamentum arteriosum.4 The mirror image of this anomaly, a left arch with right descending aorta, has also been described.11
Right aortic arch with aberrant brachiocephalic (innominate) A rare type of right aortic arch that forms a vascular ring is one in which the left common carotid and left subclavian artery course behind the esophagus as a result of involution of the left fourth embryonic aortic arch between the ascending aorta and left common carotid artery.12 Most patients present in childhood, although symptoms may not appear in adulthood.
Right aortic arch with isolated left subclavian artery An isolated left subclavian artery is a rare anomaly and occurs when the left fourth embryonic aortic arches regresses between the left common carotid and left subclavian arteries as well as between the ligamentum arteriosum and the descending aorta.13 The isolated left subclavian artery is usually supplied by a patent ductus arteriosus. When the ductus is closed, flow comes from the left vertebral artery, collaterals, or both.
Double aortic arch Double aortic arch (Figs. 9 and 10) is the most common symptomatic vascular ring, occurring in 0.05%–0.3% of
Figure 5 (A) Contrast-enhanced CT image shows a right aortic arch (arrow). (B) Contrast-enhanced CT image more cephalad shows mirror-image branching of the left brachiocephalic (arrowhead), right common carotid (wide arrow), and right subclavian arteries (thin arrow). (C) Three-dimensional volume-rendered image from a contrast-enhanced CT scan of a different patient shows a right aortic arch with mirror image branching of the left brachiocephalic (thin arrow), right common carotid (wide arrow), right subclavian (arrowhead) arteries.
Kanne and Godwin
Right aortic arch and its variants
Figure 6 Schematic based on Edwards’ hypothetical embryonic double aortic arch system shows a right aortic arch with mirror image branching and retroesophageal diverticulum (arrowheads) connecting to a left ductus arteriosus (arrowhead). AA, ascending aorta; DA, descending aorta; R SCA, right subclavian artery; R CCA, right common carotid artery; L CCA, left common carotid artery; L SCA, left subclavian artery; PA, pulmonary artery; E, esophagus.
297 and the descending aorta is usually contralateral to the dominant arch. The trachea may be mildly narrowed. Rarely, in the setting of double aortic arch, atresia of one of the arch segments may occur, usually on the left (Figs. 11 and 12). The most common sites of atresia are distal to the origin of the left subclavian artery and between the left common carotid and left subclavian arteries.1,14 Distinguishing this anomaly from right aortic with mirror-image branching can be difficult. However, symmetric configuration of the subclavian and common carotid arteries originating from the right arch and a descending aortic diverticulum are characteristic of double aortic arch with segmental atresia of the distal left arch. The only exception is the extremely rare right arch with mirror-image branching and descending aortic (Kommerell) diverticulum.10
Cervical aortic arch Cervical aortic arch (Fig. 13) is a rare anomaly that usually occurs on the right (.80%) and is thought to be the
Figure 7 (A) Contrast-enhanced CT image shows a right aortic arch (arrow) with retroesophageal diverticulum (arrowhead). (B) Contrast-enhanced CT image more caudad shows the descending aorta on the right (arrow). (C) Three-dimensional volume-rendered image better shows the retroesophageal aortic diverticulum (arrow).
298
Journal of Cardiovascular Computed Tomography, Vol 4, No 5, September/October 2010
Figure 8 (A) Contrast-enhanced CT image shows a circumflex right aortic arch (arrow) with an aberrant left subclavian artery (arrowhead). The arch crosses high in the mediastinum behind the esophagus. (B) Contrast-enhanced CT image more caudad shows the descending aorta on the left (arrow). (C) Coronal oblique maximum-intensity projection shows the distal arch (arrow) crossing the mediastinum to the left. (D) Coronal oblique maximum intensity projection in a more posterior plane shows the aorta descending on the left (arrow).
result of persistence of the third embryonic aortic arch or failure of the fourth embryonic arch to descend. This anomaly is often associated with unusual origins of the internal and external carotid arteries, and the descending aorta is usually contralateral to the arch. Cervical arch can present with pulsatile neck mass, dysphagia, or upper airway obstruction.1
Conclusion
Figure 9 Schematic based on Edwards’ hypothetical embryonic double aortic arch system of a double aortic arch. AA, ascending aorta; DA, descending aorta; R SCA, right subclavian artery; R CCA, right common carotid artery; L CCA, left common carotid artery; L SCA, left subclavian artery; PA, pulmonary artery; E, esophagus; left ductus arteriosus (arrow).
A right aortic arch can occur in isolation or in association with congenital heart disease, especially tetralogy of Fallot and truncus arteriosus. Edwards’ embryologic double aortic arch model can help explain the embryogenesis of many variation of right aortic arch. Although a right aortic arch is usually identified on the chest radiograph, CT often provides definitive evaluation of suspected associated anomalies.
Kanne and Godwin
Right aortic arch and its variants
299
Figure 10 Transverse maximum-intensity projection (A) and 3-dimensional volume-rendered image (B) from a contrast-enhanced CT scan show a double aortic arch. Note the symmetric arrangement of the common carotid (arrowheads) and subclavian (arrows) arteries. AA, ascending aorta; DA, descending aorta, R, right arch; L, left arch. (Courtesy of Arlene Sirajuddin, MD, Chicago, IL.)
Figure 11 Schematic based on Edwards’ hypothesis showing atretic segment of the embryonic left arch (arrowhead) and a diverticulum (arrow), which arises from the descending aorta. AA, ascending aorta; DA, descending aorta; R SCA, right subclavian artery; R CCA, right common carotid artery; L CCA, left common carotid artery; L SCA, left subclavian artery; PA, pulmonary artery; E, esophagus; left ductus arteriosus (arrow).
Figure 12 (A) Thin-slab maximum-intensity projection from contrast-enhanced CT shows a double aortic arch with atretic distal left segment (thin white arrow). The right arch (thick white arrow) is larger than the left arch (arrowhead). Note the diverticulum arising from the descending aorta (black arrow). (B) Transverse image at the level of the thoracic inlet shows symmetry of the common carotid (arrowheads) and subclavian arteries (arrows).
300
Journal of Cardiovascular Computed Tomography, Vol 4, No 5, September/October 2010
Figure 13 (A) Coronal maximum-intensity projection from contrast-enhanced CT shows a right cervical aortic arch. The first branch is the left common carotid artery (arrow) followed by the right common carotid artery (arrowhead), which promptly bifurcates into its internal and external branches. AA, ascending aorta. (B) Coronal maximum intensity projection in more posterior plane shows the right subclavian artery (arrowhead) arising from the distal arch and the left subclavian artery (arrow) arising from the descending aorta (DA).
Acknowledgment The authors thank David W. Ehlert, MAMS, CMI, for the schematic illustrations.
7.
References
9.
8.
10. 1. Shuford WH, Sybers RG: The aortic arch and its malformations. Springfield, IL: Charles C. Thomas; 1974. 2. Holland P, Fitzpatrick JD: Case report: magnetic resonance imaging of a right-sided cervical aortic arch with a congenital aneurysm. Clin Radiol. 1991;43:352–5. 3. Hastreiter AR, D’Cruz IA, Cantez T: Right-sided aorta. Part I. Occurrence of right aortic arch in various types of congenital heart disease. Br Heart J. 1996;28:722–5. 4. Knight L, Edwards JE: Right aortic arch. Types and associated cardiac anomalies. Circulation. 1974;50:1047–51. 5. Kimura-Hayama ET, Mele´ndez G, Mendiza´bal AL, Meave-Gonza´lez A, Zambrana GF, Corona-Villalobos CP: Uncommon congenital and acquired aortic diseases: role of multidetector CT angiography. Radiographics. 2010;30:79–98. 6. Tu¨rkvatan A, Bu¨yu¨kbayraktar FG, Olc¸er T, Cumhur T: Congenital anomalies of the aortic arch: evaluation with the use of
11. 12.
13.
14.
15.
multidetector computed tomography. Korean J Radiol. 2009;10: 176–84. Edwards JE: Anomalies of the derivatives of the aortic arch system. Med Clin N Am. 1948;32:925–45. Moore KL, Persaud TVN: Before we are born. 4th ed. Philadelphia, PA: W.B. Saunders Company; 1993. Felson B, Palayew MJ: The two types of right aortic arch. Radiology. 1963;81:745–59. Garti IJ, Aygen MM, Vidne B, Levy MJ: Right aortic arch with mirror-image branching causing vascular ring. A new classification of the right aortic arch patterns. Br J Radiol. 1973;46:115–9. Dominguez R, Oh KS, Dorst JP, Young LW: Left aortic arch with right descending aorta. AJR Am J Roentgenol. 1978;130:917–20. Grollman JH Jr., Bedynek JL, Henderson HS, Hall RJ: Right aortic arch with an aberrant retroesophageal innominate artery: angiographic diagnosis. Radiology. 1968;90:782–3. Luetmer PH, Miller GM: Right aortic arch with isolation of the left subclavian artery: case report and review of the literature. Mayo Clin Proc. 1990;65:407–13. Schlesinger AE, Krishnamurthy R, Sena LM, Guillerman RP, Chung T, Dibardino DJ, Fraser CK Jr.: Incomplete double aortic arch with atresia of the distal left arch: distinctive imaging appearance. AJR Am J Roentgenol. 2005;184:1634–9. VanDyke CB, White RD: Congenital abnormalities of the thoracic aorta presenting in the adult. J Thorac Imaging. 1994;9:230–45.
Pictorial Essay
Right aortic arch and its variants Jeffrey P. Kanne, MDa,*, J. David Godwin, MDb a
Department of Radiology, University of Wisconsin School of Medicine and Public Health, MC 3252, 600 Highland Avenue, Madison, WI 53572-3252, USA and bDepartment of Radiology, University of Washington Medical Center, Seattle, WA, USA KEYWORDS: Aorta; Congenital; Right aortic arch; Double aortic arch; Computed tomography
Abstract. A number of congenital anomalies of the aortic arch complex can occur, ranging from asymptomatic normal variations in arch vessel branch pattern to symptomatic vascular rings, stenoses, and arch interruptions with a frequency ranging from 0.5% to 3.0%. A right aortic arch is present in 0.1% of the population and can occur in isolation or be associated with congenital heart disease. Patients may present at any age with signs and symptoms of airway or esophageal compression, heart failure, or abnormal chest imaging studies. This pictorial essay will show the computed tomography and appearances of congenital variations of the right aortic arch and use Edwards’ hypothetical embryonic double aortic arch model to explain the cause of some of these variants. Ó 2010 Society of Cardiovascular Computed Tomography. All rights reserved.
Introduction Congenital anomalies of the aortic arch complex range from asymptomatic normal variations in arch vessel branch pattern to symptomatic vascular rings, stenoses, and arch interruptions.1 The frequency of aortic arch anomalies ranges from 0.5% to 3.0%.2 Patients can present at any age with an abnormal chest radiograph or a variety of signs and symptoms, including dysphagia, dyspnea, hypertension, and congestive heart failure. A right aortic arch occurs in approximately 0.1% of adults.3,4 It may be an incidental finding but can be associated with congenital heart disease. Congenital right aortic arch anomalies are sometimes recognizable on chest radiographs, Conflict of interest: Jeffrey P. Kanne is a consultant for superDimension, Inc (not relevant to content of manuscript) and for PTC Therapeutics Inc (not relevant to content of manuscript). Dr Godwin reports no conflicts of interest. * Corresponding author. E-mail address: [email protected] Submitted January 11, 2010. Accepted for publication July 8, 2010.
but computed tomography (CT) and magnetic resonance imaging (MRI) more clearly show anomalies and are thus often definitive.5,6 In 1948, Edwards proposed a system that used a hypothetical embryonic double aortic arch to explain the various congenital anomalies of the aortic arch determined by the site of interruption or atresia of the embryonic arch system (Fig. 1).7 From this model, one can gain an understanding of the embryogenesis of a right aortic arch and some of its variants. This pictorial essay reviews the CT appearances of many congenital variations of the right aortic arch (Table 1) and use Edwards’ embryonic double arch model to show the embryogenesis of some of these anomalies. Anomalies are discussed in decreasing frequency as they are encountered in the adult.
Embryology The aorta and its branches develop early in embryogenesis.8 During the fourth week of embryogenesis the
1934-5925/$ - see front matter Ó 2010 Society of Cardiovascular Computed Tomography. All rights reserved. doi:10.1016/j.jcct.2010.07.002
294
Journal of Cardiovascular Computed Tomography, Vol 4, No 5, September/October 2010 arches have no known derivatives. The proximal segment of the left sixth embryonic aortic arch becomes the left pulmonary artery, and its distal segment becomes the ductus arteriosus. The proximal segment of the right sixth embryonic aortic arch becomes the right pulmonary artery, and the distal segment involutes. Failure of normal development, segmentation, or regression of these embryonic aortic arches leads to the multiple aortic arch anomalies that have been described. Some aortic arch anomalies occur in isolation, whereas others are frequently associated with congenital heart disease.
Right aortic arch Figure 1 Schematic based on Edwards’ hypothetical embryonic double aortic arch. AA, ascending aorta; DA, descending aorta; R SCA, right subclavian artery; R CCA, right common carotid artery; L CCA, left common carotid artery; L SCA, left subclavian artery; PA, pulmonary artery; ducti arteriosi (arrows).
branchial (pharyngeal) arches form, and their arterial supply comes from the heart. These 6 paired arteries arise from the aortic sac and terminate in the ipsilateral dorsal aorta, forming embryonic aortic arches. The aortic arches do not all exist at the same time, with some already gone when others appear. The primitive pattern of embryonic aortic arches takes on the adult pattern during the sixth through eighth weeks of embryogenesis. The first and second paired embryonic aortic arches regress. The third paired embryonic aortic arches form the common carotid arteries, and their distal segments form the internal carotid arteries in conjunction with the dorsal aortae. Normally, the left fourth embryonic aortic arch forms a portion of the adult aortic arch, and the right fourth embryonic aortic arch forms the right subclavian artery. However, an adult right aortic arch forms when this pattern is reversed. The paired fifth embryonic aortic
Table 1
The most common form of right aortic arch in adults is associated with an aberrant left subclavian artery (Figs. 2 and 3),9 which originates as the last arch vessel and crosses the mediastinum from right to left posterior to the esophagus. The incidence of associated congenital heart disease is low, with most patients having tetralogy of Fallot.4 Sometimes the origin of the aberrant left subclavian artery has a bulb-like dilation called the diverticulum of Kommerell, which develops from the remnant of the embryonic left fourth aortic arch. A diverticulum of Kommerell implies a left ligamentum arteriosum is present, forming a vascular ring. However, most patients with this configuration are usually asymptomatic, indicating the vascular ring is quite loose. A diverticulum of Kommerell, particularly when large, can indent the posterior wall of the esophagus and trachea, resulting in symptoms.
Mirror-image branching Mirror-image branching of the arch vessels is the most common form of right aortic arch and is associated with
Right aortic arch anomalies
Anomaly
Descending aorta
Subclavian artery
R R R R R
Right Right Right Left Right
Normal Normal Aberrant Aberrant Aberrant brachiocephalic Isolated left Normal
arch, arch, arch, arch, arch,
Aberrant left subclavian artery
mirror image branching circumflex ligamentum aberrant L subclavian aberrant L subclavian aberrant brachiocephalic
R arch, isolated L subclavian Double arch
Right Left . right
CHD, congenital heart disease; L, left; R, right. Adapted from VanDyke and White.15
Ductus
Frequency
Vascular ring
Associated CHD
Usually left Left descending Left Left Unknown
Common Rare Common Rare Rare
No Yes Yes Yes Possible
Almost always No Uncommon Yes Unknown
Left, usually patent Usually left
Rare Common
Possible Yes
Yes Rare
Kanne and Godwin
Right aortic arch and its variants
295 congenital heart disease, nearly always cyanotic, in approximately 98% of patients (Figs. 4 and 5). Most patients with this pattern of right aortic arch present in childhood. Approximately 25% of patients with tetralogy of Fallot and 25%–50% of patients with truncus arteriosus have right aortic arch with mirror-image branching. A rare variant of this anomaly forms a vascular ring with a retroesophageal aortic diverticulum connecting to the left ductus arteriosus (Figs. 6 and 7).10 Because of the extremely high association with cyanotic congenital heart disease, cardiac morphology is almost always abnormal on imaging studies. Comprehensive evaluation relies on echocardiography, CT, MRI, or a combination.
Right aortic arch with left descending aorta Figure 2 Schematic based on Edwards’ hypothetical embryonic double aortic arch system shows a right aortic arch with aberrant left subclavian artery. AA, ascending aorta; DA, descending aorta; R SCA, right subclavian artery; R CCA, right common carotid artery; L CCA, left common carotid artery; L SCA, left subclavian artery; PA, pulmonary artery.
An uncommon variant of right aortic arch, sometimes referred to as a circumflex aorta or retroesophageal aortic segment,4 is one in which the transverse arch courses posterior to the esophagus and continues as a left descending aorta (Fig. 8). This anomaly may be a variant of double aortic arch
Figure 3 (A) Contrast-enhanced CT image shows a right aortic arch (thin arrow) with an aberrant left subclavian artery (arrowhead). Left brachiocephalic artery (wide arrow). (B) Contrast-enhanced CT image more caudad shows the descending aorta on the right (arrow) and a small persistent left superior vena cava (arrowhead). (C) Coronal maximum-intensity projection shows the aberrant left subclavian artery (thin arrow) arising from a large retroesophageal diverticulum of Kommerell (*). The right common carotid (arrowhead) and subclavian arteries (wide arrow) arise normal. The descending aorta (curved arrow) travels back to the right as it descends.
296
Journal of Cardiovascular Computed Tomography, Vol 4, No 5, September/October 2010 the population.4,14 In infants, it usually presents with stridor or difficulty in feeding. However, patients with this anomaly can remain asymptomatic or present later in life. There is no increased incidence of congenital heart disease with double aortic arch. On CT, the right arch is larger, posterior, and more cephalad than the left arch in about two-thirds of patients,
Figure 4 Schematic based on Edwards’ hypothetical embryonic double aortic arch system shows right aortic arch with mirror image branching. AA, ascending aorta; DA, descending aorta; R SCA, right subclavian artery; R CCA, right common carotid artery; L CCA, left common carotid artery; L SCA, left subclavian artery; PA, pulmonary artery; left ductus arteriosus (arrow).
with focal left arch atresia. A symptomatic vascular ring is formed in the setting of an aberrant left subclavian artery and a left ligamentum arteriosum.4 The mirror image of this anomaly, a left arch with right descending aorta, has also been described.11
Right aortic arch with aberrant brachiocephalic (innominate) A rare type of right aortic arch that forms a vascular ring is one in which the left common carotid and left subclavian artery course behind the esophagus as a result of involution of the left fourth embryonic aortic arch between the ascending aorta and left common carotid artery.12 Most patients present in childhood, although symptoms may not appear in adulthood.
Right aortic arch with isolated left subclavian artery An isolated left subclavian artery is a rare anomaly and occurs when the left fourth embryonic aortic arches regresses between the left common carotid and left subclavian arteries as well as between the ligamentum arteriosum and the descending aorta.13 The isolated left subclavian artery is usually supplied by a patent ductus arteriosus. When the ductus is closed, flow comes from the left vertebral artery, collaterals, or both.
Double aortic arch Double aortic arch (Figs. 9 and 10) is the most common symptomatic vascular ring, occurring in 0.05%–0.3% of
Figure 5 (A) Contrast-enhanced CT image shows a right aortic arch (arrow). (B) Contrast-enhanced CT image more cephalad shows mirror-image branching of the left brachiocephalic (arrowhead), right common carotid (wide arrow), and right subclavian arteries (thin arrow). (C) Three-dimensional volume-rendered image from a contrast-enhanced CT scan of a different patient shows a right aortic arch with mirror image branching of the left brachiocephalic (thin arrow), right common carotid (wide arrow), right subclavian (arrowhead) arteries.
Kanne and Godwin
Right aortic arch and its variants
Figure 6 Schematic based on Edwards’ hypothetical embryonic double aortic arch system shows a right aortic arch with mirror image branching and retroesophageal diverticulum (arrowheads) connecting to a left ductus arteriosus (arrowhead). AA, ascending aorta; DA, descending aorta; R SCA, right subclavian artery; R CCA, right common carotid artery; L CCA, left common carotid artery; L SCA, left subclavian artery; PA, pulmonary artery; E, esophagus.
297 and the descending aorta is usually contralateral to the dominant arch. The trachea may be mildly narrowed. Rarely, in the setting of double aortic arch, atresia of one of the arch segments may occur, usually on the left (Figs. 11 and 12). The most common sites of atresia are distal to the origin of the left subclavian artery and between the left common carotid and left subclavian arteries.1,14 Distinguishing this anomaly from right aortic with mirror-image branching can be difficult. However, symmetric configuration of the subclavian and common carotid arteries originating from the right arch and a descending aortic diverticulum are characteristic of double aortic arch with segmental atresia of the distal left arch. The only exception is the extremely rare right arch with mirror-image branching and descending aortic (Kommerell) diverticulum.10
Cervical aortic arch Cervical aortic arch (Fig. 13) is a rare anomaly that usually occurs on the right (.80%) and is thought to be the
Figure 7 (A) Contrast-enhanced CT image shows a right aortic arch (arrow) with retroesophageal diverticulum (arrowhead). (B) Contrast-enhanced CT image more caudad shows the descending aorta on the right (arrow). (C) Three-dimensional volume-rendered image better shows the retroesophageal aortic diverticulum (arrow).
298
Journal of Cardiovascular Computed Tomography, Vol 4, No 5, September/October 2010
Figure 8 (A) Contrast-enhanced CT image shows a circumflex right aortic arch (arrow) with an aberrant left subclavian artery (arrowhead). The arch crosses high in the mediastinum behind the esophagus. (B) Contrast-enhanced CT image more caudad shows the descending aorta on the left (arrow). (C) Coronal oblique maximum-intensity projection shows the distal arch (arrow) crossing the mediastinum to the left. (D) Coronal oblique maximum intensity projection in a more posterior plane shows the aorta descending on the left (arrow).
result of persistence of the third embryonic aortic arch or failure of the fourth embryonic arch to descend. This anomaly is often associated with unusual origins of the internal and external carotid arteries, and the descending aorta is usually contralateral to the arch. Cervical arch can present with pulsatile neck mass, dysphagia, or upper airway obstruction.1
Conclusion
Figure 9 Schematic based on Edwards’ hypothetical embryonic double aortic arch system of a double aortic arch. AA, ascending aorta; DA, descending aorta; R SCA, right subclavian artery; R CCA, right common carotid artery; L CCA, left common carotid artery; L SCA, left subclavian artery; PA, pulmonary artery; E, esophagus; left ductus arteriosus (arrow).
A right aortic arch can occur in isolation or in association with congenital heart disease, especially tetralogy of Fallot and truncus arteriosus. Edwards’ embryologic double aortic arch model can help explain the embryogenesis of many variation of right aortic arch. Although a right aortic arch is usually identified on the chest radiograph, CT often provides definitive evaluation of suspected associated anomalies.
Kanne and Godwin
Right aortic arch and its variants
299
Figure 10 Transverse maximum-intensity projection (A) and 3-dimensional volume-rendered image (B) from a contrast-enhanced CT scan show a double aortic arch. Note the symmetric arrangement of the common carotid (arrowheads) and subclavian (arrows) arteries. AA, ascending aorta; DA, descending aorta, R, right arch; L, left arch. (Courtesy of Arlene Sirajuddin, MD, Chicago, IL.)
Figure 11 Schematic based on Edwards’ hypothesis showing atretic segment of the embryonic left arch (arrowhead) and a diverticulum (arrow), which arises from the descending aorta. AA, ascending aorta; DA, descending aorta; R SCA, right subclavian artery; R CCA, right common carotid artery; L CCA, left common carotid artery; L SCA, left subclavian artery; PA, pulmonary artery; E, esophagus; left ductus arteriosus (arrow).
Figure 12 (A) Thin-slab maximum-intensity projection from contrast-enhanced CT shows a double aortic arch with atretic distal left segment (thin white arrow). The right arch (thick white arrow) is larger than the left arch (arrowhead). Note the diverticulum arising from the descending aorta (black arrow). (B) Transverse image at the level of the thoracic inlet shows symmetry of the common carotid (arrowheads) and subclavian arteries (arrows).
300
Journal of Cardiovascular Computed Tomography, Vol 4, No 5, September/October 2010
Figure 13 (A) Coronal maximum-intensity projection from contrast-enhanced CT shows a right cervical aortic arch. The first branch is the left common carotid artery (arrow) followed by the right common carotid artery (arrowhead), which promptly bifurcates into its internal and external branches. AA, ascending aorta. (B) Coronal maximum intensity projection in more posterior plane shows the right subclavian artery (arrowhead) arising from the distal arch and the left subclavian artery (arrow) arising from the descending aorta (DA).
Acknowledgment The authors thank David W. Ehlert, MAMS, CMI, for the schematic illustrations.
7.
References
9.
8.
10. 1. Shuford WH, Sybers RG: The aortic arch and its malformations. Springfield, IL: Charles C. Thomas; 1974. 2. Holland P, Fitzpatrick JD: Case report: magnetic resonance imaging of a right-sided cervical aortic arch with a congenital aneurysm. Clin Radiol. 1991;43:352–5. 3. Hastreiter AR, D’Cruz IA, Cantez T: Right-sided aorta. Part I. Occurrence of right aortic arch in various types of congenital heart disease. Br Heart J. 1996;28:722–5. 4. Knight L, Edwards JE: Right aortic arch. Types and associated cardiac anomalies. Circulation. 1974;50:1047–51. 5. Kimura-Hayama ET, Mele´ndez G, Mendiza´bal AL, Meave-Gonza´lez A, Zambrana GF, Corona-Villalobos CP: Uncommon congenital and acquired aortic diseases: role of multidetector CT angiography. Radiographics. 2010;30:79–98. 6. Tu¨rkvatan A, Bu¨yu¨kbayraktar FG, Olc¸er T, Cumhur T: Congenital anomalies of the aortic arch: evaluation with the use of
11. 12.
13.
14.
15.
multidetector computed tomography. Korean J Radiol. 2009;10: 176–84. Edwards JE: Anomalies of the derivatives of the aortic arch system. Med Clin N Am. 1948;32:925–45. Moore KL, Persaud TVN: Before we are born. 4th ed. Philadelphia, PA: W.B. Saunders Company; 1993. Felson B, Palayew MJ: The two types of right aortic arch. Radiology. 1963;81:745–59. Garti IJ, Aygen MM, Vidne B, Levy MJ: Right aortic arch with mirror-image branching causing vascular ring. A new classification of the right aortic arch patterns. Br J Radiol. 1973;46:115–9. Dominguez R, Oh KS, Dorst JP, Young LW: Left aortic arch with right descending aorta. AJR Am J Roentgenol. 1978;130:917–20. Grollman JH Jr., Bedynek JL, Henderson HS, Hall RJ: Right aortic arch with an aberrant retroesophageal innominate artery: angiographic diagnosis. Radiology. 1968;90:782–3. Luetmer PH, Miller GM: Right aortic arch with isolation of the left subclavian artery: case report and review of the literature. Mayo Clin Proc. 1990;65:407–13. Schlesinger AE, Krishnamurthy R, Sena LM, Guillerman RP, Chung T, Dibardino DJ, Fraser CK Jr.: Incomplete double aortic arch with atresia of the distal left arch: distinctive imaging appearance. AJR Am J Roentgenol. 2005;184:1634–9. VanDyke CB, White RD: Congenital abnormalities of the thoracic aorta presenting in the adult. J Thorac Imaging. 1994;9:230–45.