British Journal of Radiology (2003) 76, 491-502
© 2003 British Institute of Radiology
doi: 10.1259/bjr/14043447
Developmental abnormalities of the great vessels of the thorax and their embryological basis
M Davies, FRCR and
P J Guest, FRCR
Department of Radiology, The Queen Elizabeth Hospital, Edgbaston, Birmingham B15 2TH, UK
Correspondence: P J Guest
 |
Abstract
|
|---|
Congenital abnormalities of the thoracic vascular system are commonly encountered in radiological practice. A pictorial review of these abnormalities using a variety of imaging modalities is presented and their embryological basis described. A knowledge of their embryological derivation helps the understanding of these abnormalities.
|
Introduction
|
|---|
Congenital abnormalities of the aortic arch and great vessels are often encountered in radiological practice. They may be discovered incidentally on imaging, when they are important to recognise and distinguish from serious pathology, or present with symptoms [1].
The purpose of this pictorial review is to demonstrate developmental abnormalities of the thoracic vascular system with a variety of imaging modalities and to explain their embryological basis. Congenital disease of the heart itself is not within the remit of this review.
|
Systemic arterial system
|
|---|
Initially the embryo has two dorsal aortae that communicate with an aortic sac via several pairs of branchial arch arteries. The branchial arch arteries are not all present at any one time. The aortic sac communicates with the heart via the truncus arteriosus, which later divides into the pulmonary trunk and ascending aorta [2].
During embryological development this primitive pattern is transformed into the adult pattern by involution of particular vascular segments (Figure 1
). The right dorsal aorta largely involutes. The first, second and fifth pairs of arch arteries involute. The third pair of arch arteries forms the common and proximal internal carotid arteries. The left fourth arch artery becomes part of the aortic arch while the right fourth arch artery becomes the root of the right subclavian artery. The left subclavian artery is derived entirely from an intersegmental artery arising directly from the dorsal aorta. The brachiocephalic trunk arises from the aortic sac [2].
View larger version (51K):
[in this window]
[in a new window]
|
Figure 1. Diagrams showing transformation of the early aortic arch pattern (6–8 weeks) into the adult pattern. Reproduced with permission, Moore KL. The developing human: clinically orientated embryology. WB Saunders Company, 1982.
|
|
Double aortic arch
This occurs when the caudal most part of the right dorsal aorta fails to involute (Figure 2). A complete vascular ring results, the right arch usually being higher and wider than the left (Figure 3).
View larger version (39K):
[in this window]
[in a new window]
|
Figure 2. Diagram showing the embryological basis of a double aortic arch. Reproduced with permission, Moore KL. The developing human: clinically orientated embryology. WB Saunders Company, 1982.
|
|
Right-sided aortic arch
This results from persistence of the entire right dorsal arch and involution of a segment of the left arch (Figure 4). The arch lies to the right of the spine before descending on either the right or the left of the spine.
View larger version (102K):
[in this window]
[in a new window]
|
Figure 4. Detail of (a) chest radiograph and (b) axial MR image in a patient with a right-sided aortic arch. Note the right paratracheal "mass" (arrows) with tracheal displacement to the left in (a) and superior vena cava (SVC) (large arrow) and trachea (small arrow) in (b). A central venous catheter is present in the SVC in (a).
|
|
There are 2 main types:
(a) Right aortic arch with aberrant left subclavian artery (ALSCA): There are four branches of the arch, the ALSCA being the last branch which passes to the left behind the oesophagus. The ALSCA may arise from an aortic diverticulum representing a remnant of the distal primitive left arch [3].
(b) Right aortic arch with mirror image branching: The arch gives origin to three branches: left brachiocephalic trunk; right common carotid; and right subclavian (Figure 5). It is therefore a "mirror image" of the normal anatomy. There is a far higher incidence of severe congenital heart disease in individuals with "mirror image" right sided arch with almost all having cyanotic heart disease, usually due to tetralogy of Fallot.
View larger version (39K):
[in this window]
[in a new window]
|
Figure 5. Diagram showing the embryological basis of a right-sided aortic arch without a retro-oesophageal component. Reproduced with permission, Moore KL. The developing human: clinically orientated embryology. WB Saunders Company, 1982.
|
|
Cervical arch
The aortic arch extends high into the upper mediastinum or lower cervical region (Figure 6). Its embryological origin is contentious. It is more common on the right when the entire right third arch and right dorsal aorta persist as the definitive aortic arch [4]. Its branches are variable, but the right subclavian, internal and external carotid arteries often arise independently from the arch [4].
View larger version (100K):
[in this window]
[in a new window]
|
Figure 6. Intravenous digitally subtracted angiogram (a), with corresponding line diagram (b), demonstrating a large aneurysm arising from a cervical aortic arch. Note that the cervical arch (large arrow) extends above the clavicle (small arrows). The common carotid arteries are indicated with arrow heads.
|
|
Aberrant right subclavian artery
Aberrant right subclavian artery (ARSCA) affects approximately 0.1% of the population and is often an incidental finding on imaging studies. It occurs when the right fourth aortic arch and right dorsal aorta involute cranial to the seventh intersegmental artery (Figure 7). The ARSCA arises from the descending aorta or a diverticulum and crosses to the right behind the oesophagus (Figure 8).
View larger version (21K):
[in this window]
[in a new window]
|
Figure 7. Diagram showing the embryological basis of an aberrant right subclavian artery. Reproduced with permission, Moore KL. The developing human: clinically orientated embryology. WB Saunders Company, 1982.
|
|
View larger version (89K):
[in this window]
[in a new window]
|
Figure 8. (a) Barium swallow and (b) contrast enhanced CT image in a patient with an aneurysm arising from an aberrant right subclavian artery. Note the posterior vascular impression on the oesophagus in (a).
|
|
Aortic coarctation
This occurs when there is partial involution of the left dorsal aortic arch (Figures 9a,b). Pre-ductal coarctation results when partial involution of the dorsal aorta occurs cranial to the left sixth arch artery and post-ductal coarctation when the involution is distal. Collateral blood flow via intercostal arteries may result in notching of the inferior aspect of the third to eighth ribs. Such inferior rib notching is bilateral in post-ductal coarctation, right sided in pre-ductal coarctation and left sided in coarctation associated with an ARSCA (Figure 9c).
View larger version (113K):
[in this window]
[in a new window]
|
Figure 9. (a) Diagrammatic explanation of the embryological basis for aortic coarctation. Reproduced with permission, Moore KL. The developing human: clinically orientated embryology. WB Saunders Company, 1982. (b) Parasagittal cine MRI showing an aortic coarctation (arrow). (c) Detail of a chest radiograph showing left-sided inferior rib notching (arrows) due to collateral circulation in a patient with post-ductal aortic coarctation.
|
|
|
Pulmonary arterial system
|
|---|
The proximal portions of the right and left sixth arch arteries form the proximal right and left pulmonary arteries, respectively. The distal part of the left sixth arch forms the ductus arteriosus and the distal part of the right sixth arch involutes. Buds from the sixth arch arteries grow into the primitive lungs and anastomose with the primitive pulmonary circulation [2]. A patent ductus arteriosus results from failure of the ductus to close after birth and is the third most common cause of a left-to-right shunt after atrial and ventricular septal defects (Figure 10). Unlike the others, a patent ductus arteriosus is associated with a large ascending aorta and aortic arch, allowing the diagnosis to be suggested on a chest radiograph.
Absence of a pulmonary artery
This uncommon anomaly may be due to abnormal involution of the proximal sixth primitive arch artery on that side. The blood supply to the lung is via bronchial arteries or an ipsilateral patent ductus arising from the arch. There is a corresponding reduction in size of the affected lung which can be detected on a chest radiograph (Figures 11 and 12)
View larger version (140K):
[in this window]
[in a new window]
|
Figure 11. Posterior view of a perfusion scintigram in a patient with an absent right pulmonary artery. Incidental finding on investigation for possible pulmonary emboli.
|
|
View larger version (102K):
[in this window]
[in a new window]
|
Figure 12. Axial MRI of absent left pulmonary artery (PA). Note absent left PA and hypoplastic ipsilateral hemithorax. The descending aorta is right-sided (arrow).
|
|
Anomalous left pulmonary artery (pulmonary sling)
This rare anomaly is probably due to involution of the proximal left sixth arch [4]. An anastomotic vessel linking the primitive pulmonary circulations becomes the anomalous left pulmonary artery which arises from the right pulmonary artery and courses to the left, passing between the trachea and oesophagus. A vascular sling occurs, which may cause repeated pulmonary infections by tracheal compression (Figure 13).
View larger version (98K):
[in this window]
[in a new window]
|
Figure 13. Contrast enhanced CT image showing a left pulmonary artery originating from the right pulmonary artery (pulmonary sling) forming a loop behind the trachea (arrow) with collapse/consolidation of the right lung. (Courtesy of Dr H Alton.)
|
|
|
Systemic venous system
|
|---|
Initially the cardinal veins constitute the main venous drainage of the embryo (Figure 14a). Paired anterior and posterior cardinal veins drain into the sinus venosus via common cardinal veins. The right horn of the sinus venosus becomes incorporated into the right atrium and the left horn becomes the coronary sinus. The posterior cardinal veins largely involute [2].
View larger version (23K):
[in this window]
[in a new window]
|
Figure 14. Primitive veins of the thorax at 6 weeks (a) and the adult venous pattern (b). (Reproduced with permission, Moore KL. The developing human: clinically orientated embryology. WB Saunders Company, 1982.)
|
|
The anterior cardinal veins become connected by an oblique anastamosis and the proximal part of the left anterior cardinal vein regresses. This oblique anastamosis will form the left brachiocephalic vein while the right anterior and common cardinal veins form the superior vena cava (SVC) (Figure 14b
).
Double and left-sided SVC
If the oblique vascular channel fails to form, both anterior cardinal veins persist to form a double SVC, with the left SVC draining into the right atrium via the coronary sinus.
Alternatively, an oblique vascular channel may become established but the proximal part of the right anterior cardinal vein regresses. A left-sided SVC results which again drains into the right atrium via the coronary sinus (Figure 15). Rarely, a left-sided SVC may drain into the left atrium.
View larger version (70K):
[in this window]
[in a new window]
|
Figure 15. Left-sided superior vena cava: (a) chest radiograph and (b) unenhanced CT. Note in (a) a left paramediastinal opacity fading superiorly (arrows) and absence of a normal similar structure on the right. In (b) the left-sided superior vena cava is indicated with an arrow.
|
|
|
Pulmonary venous system
|
|---|
The primitive lung begins as an outgrowth from the foregut and the venous drainage is via a vascular plexus that communicates with the cardinal venous system. Subsequently a single pulmonary vein grows from the left atrium to join this primitive venous plexus and the connections with the cardinal venous system are largely obliterated. Absorption of this single vein into the atrial wall beyond its second branch point results in a variable number of pulmonary veins [2].
Anomalous pulmonary venous drainage
Failure of the primitive pulmonary vein to develop results in all the pulmonary venous drainage entering the cardinal venous system. Total anomalous pulmonary venous drainage (TAPVD) results, which can be supracardiac, cardiac or infracardiac.
Alternatively, the primitive pulmonary vein can develop normally, but the pulmonary venous plexus only partially involute. A partial anomalous pulmonary venous drainage (PAPVD) results, which may drain into the right atrium, SVC, inferior vena cava, or azygos veins (Figures 16 and 17) [5]. PAPVD is frequently associated with atrial septal defects.
View larger version (154K):
[in this window]
[in a new window]
|
Figure 16. Partial anomalous pulmonary venous drainage. Chest radiograph showing a vascular opacity draining from the right lower zone to below the diaphragm – scimitar syndrome (arrows). (Courtesy of Dr S Darby.)
|
|
View larger version (53K):
[in this window]
[in a new window]
|
Figure 17. Partial anomalous pulmonary venous drainage. CT showing (a) origin of an anomalous pulmonary vein and (b) its drainage into the brachiocephalic vein (arrows).
|
|
Congenital pulmonary varices
These rare abnormalities are intrapulmonary veins that form when there is absence of a segmental or larger pulmonary vein. They drain normally into the left atrium and are usually incidental findings on chest radiographs or at angiography [6].
Received for publication November 2, 2001.
Revision received February 6, 2002.
Accepted for publication May 19, 2003.
|
References
|
|---|
- Jaffe RB. Radiographic manifestations of congenital anomalies of the aortic arch. Radiol Clin North Am 1991;29:319–34.[Medline]
- Moore KL. The circulatory system. In: Moore KL. The developing human: clinically orientated embryology, Third Edn. WB Saunders Company, 1982:298–338.
- Salomonowitz E, Edwards JE, Hunter DW, Castaneda-Zuniga WR, Lund G, Cragg AH, et al. The three types of aortic diverticula. AJR Am J Roentgenol 1984;142:673–9.[Free Full Text]
- Arey JB. Malformations of the aorta and aortic arches. In: Arey JB, editor. Cardiovascular pathology in infants and children. WB Saunders Company, 1984:242–4.
- Grainger RG. Congenital heart disease: other congenital heart lesions. In: Grainger RG, Allison DJ, editors. Diagnostic radiology; an anglo-american textbook of imaging. Churchill Livingstone, 1986:535.
- Bartram C, Strickland B. Pulmonary varices. Br J Radiol 1971;44:927–35.[Medline]
This article has been cited by other articles:
|
|
|
|
 
B Oguz, M Haliloglu, and M Karcaaltincaba
Paediatric multidetector CT angiography: spectrum of congenital thoracic vascular anomalies
Br. J. Radiol.,
May 1, 2007;
80(953):
376 - 383.
[Abstract]
[Full Text]
[PDF]
|
|
|
Top
Abstract
Introduction
