• Users Online: 171
  • Print this page
  • Email this page


 
 Table of Contents  
FOCUS ISSUE - CONGENITAL HEART DISEASE
Year : 2020  |  Volume : 4  |  Issue : 3  |  Page : 350-361

Aortic Arch Anomalies and Pulmonary Artery Anomalies : Echocardiographic Evaluation


Senior Consultant Pediatric Cardiology, Department of Pediatric Cardiology, Narayana Multispecialty Hospital, Jaipur, Rajasthan, India

Date of Submission21-Aug-2020
Date of Acceptance02-Oct-2020
Date of Web Publication18-Dec-2020

Correspondence Address:
Dr. Prashant Mahawar
Narayana Multispecialty Hospital, Rana Sanga Marg, Sector 28, Pratap Nagar, Jaipur - 302 033, Rajasthan
India
Login to access the Email id

Source of Support: None, Conflict of Interest: None


DOI: 10.4103/jiae.jiae_54_20

Rights and Permissions
  Abstract 

Congenital variants and anomalies of the aortic arch are important to recognize as they may be associated with vascular rings, congenital heart disease, and chromosomal abnormalities, and can have important implications for prognosis and management. The purpose of this article is to describe the embryology and anatomy of the aortic arch system, discuss aortic arch variants and review other malformations of the aortic arch, including interrupted aortic arch (IAA), hypoplastic aortic arch, and coarctation of aorta. I have also described few anomalies of pulmonary artery (PA) origin and bifurcation like PA sling which has clinical presentation similar to vascular ring and anomalous origin of PA from aorta which present as large aorto-pulmonary communication with congestive heart failure. Aortic arch variants and anomalies will be reviewed in the context of a theoretical double aortic arch system. Arch anomalies can be associated with symptoms, such as dysphagia lusoria in the setting of left aortic arch with aberrant right subclavian artery. Arch variants that form a vascular ring, such as double aortic arch, can result in respiratory distress due to tracheal compression.

Keywords: Arch anomalies, pulmonary artery anomalies, pulmonary artery sling, vascular ring


How to cite this article:
Mahawar P. Aortic Arch Anomalies and Pulmonary Artery Anomalies : Echocardiographic Evaluation. J Indian Acad Echocardiogr Cardiovasc Imaging 2020;4:350-61

How to cite this URL:
Mahawar P. Aortic Arch Anomalies and Pulmonary Artery Anomalies : Echocardiographic Evaluation. J Indian Acad Echocardiogr Cardiovasc Imaging [serial online] 2020 [cited 2021 Apr 13];4:350-61. Available from: https://www.jiaecho.org/text.asp?2020/4/3/350/303945


  Introduction Top


Congenital variants and anomalies of the aortic arch are important to recognize as they may be associated with vascular rings, congenital heart disease (CHD), and chromosomal abnormalities, and can have important implications for prognosis and management. Aortic arch variants and anomalies will be reviewed in the context of a theoretical double aortic arch system. Arch anomalies can be associated with symptoms, such as dysphagia lusoria in the setting of the left aortic arch with the aberrant right subclavian artery (ARSA). Arch variants that form a vascular ring, such as a double aortic arch, can result in respiratory distress due to tracheal compression. Certain arch anomalies are strongly associated with CHD, including right aortic arch (RAA) with mirror image branching. Other malformations of the aortic arch have important associations, such as Type B interrupted aortic arch (IAA), which is associated with a locus 22q11.2 microdeletion.[1]


  Embryology Top


The Rathke diagram

Martin Heinrich Rathke is credited with much of the work leading to the understanding of the embryologic development of the branchial arches; the classic Rathke diagram.

Development of the branchial apparatus begins during the 2nd week of gestation and is completed by the 7th week. The apparatus consists of six branchial arches in the wall of the foregut. The branchial arches are numbered 1–6 from cephalad to caudal. Each of the branchial arches connects paired dorsal and ventral aortas. Although the classic Rathke diagram shows six aortic arches, in reality, the arches appear and disappear at different times. The six branchial aortic arches normally develop into the thoracic aorta and its branches. The first two arches involute before the development of the sixth arch and the fifth arch is atretic or never fully develops. The third arch and portions of the ventral and dorsal aortic arches contribute to the head-and-neck arteries. The fourth arch becomes the aortic arch, and the pulmonary arteries develop from the sixth branchial arches. On the right side, the dorsal contribution of the sixth arch disappears, and on the left, it persists as the ductus arteriosus. The intersegmental arteries migrate and form the subclavian arteries [Figure 1]a and [Figure 1]b.
Figure 1: (a and b) The development of the normal aortic arch and its branches from the Rathke diagram. (a) Black-shaded branchial arch segments (numbers 1, 2, 5) represent portions of arches that disappear. Red branchial arches (numbers 3, 4, 6) remain and develop into arteries. (b) Fourth arch develops into the aortic arch (number 4). The ventral bud of the sixth arch evolves into the pulmonary artery (number 6). Portions of the third arch (number 3) and ventral portions of branchial arches contribute to left common, external and internal carotid arteries (arrows). Long thin arrows indicate cranial migration of intersegmental arteries, which later form subclavian arteries. LCCA: Left common carotid artery, LECA: Left external carotid artery, LICA: Left internal carotid artery, RCCA: Right common carotid artery, RECA: Right external carotid artery, RICA: Right internal carotid artery

Click here to view


The Edwards hypothetical double arch

Another concept that helps to understand the development of thoracic aortic anomalies is the Edwards hypothetical double arch. Jessie E. Edwards developed a diagram of a hypothetical double arch system to help explain the derivation of thoracic arch anomalies [Figure 2]. The diagram shows a double aortic arch with a ductus arteriosus on each side. Specific anomalies can be explained by showing the effect of interrupting the double arch at different locations. However, this model does not explain the lateral position of the descending thoracic aorta or the eventual size of vessels, which are important limitations.
Figure 2: The Edward hypothetical double arch. Bilateral common carotid arteries and subclavian arteries arise from each of the 2 aortic arches as independent arteries. The ventral portions of the sixth branchial arches form the pulmonary artery and the dorsal portions of the sixth branchial arch become ductus arteriosus. The seventh intersegmental arteries assume a position between PDA and common carotid arteries. LCCA: Indicates left common carotid artery, LDA: Left ductus arteriosus, LECA: Left external carotid artery, LICA: Left internal carotid artery, LPA: Left pulmonary artery, LSA: Left subclavian artery, RCCA: Right common carotid artery, RDA: Right ductus arteriosus, RECA: Right external carotid artery, RICA: Right internal carotid artery, RPA: Right pulmonary artery, RSA: Right subclavian artery

Click here to view



  Classification of Aortic Arch Anomalies Top


Aortic arch anomalies can be classified according to the Edwards hypothetical double arch system, although many modifications of this classification system have been proposed.[2]

Anatomical classification is based on the absence, narrowing, course, or position of the aortic arch and pattern of branching of great vessels.

  • Left-sided aortic arch and its variants
  • Right-sided aortic arch and its variants
  • Double aortic arch
  • Cervical aortic arch
  • Persistent fifth aortic arch
  • Interrupted aortic arch and its variants
  • Coarctation of aorta, pseudocoarctation and hypoplastic arch.


Aortic arch anomalies can also be classified based on their clinical presentation as:

  1. Asymptomatic cases
  2. Clinical symptoms caused by tracheobronchial and/or esophageal compression by vascular rings
  3. Isolation of aortic arch branches and alteration of normal blood flow with a “steal” phenomenon from the cerebral circulation.[3]


Echocardiography cannot diagnose all the above-mentioned arch anomalies; in some cases, we need computed tomography (CT) angiography or magnetic resonance imaging (MRI) for the detection and confirmation. In this article, we will focus in detail on those variants which can be picked up on echo.


  Left Aortic Arch and Its Variants Top


Based on the branching pattern of the great vessels, the left aortic arch can be divided into three groups:

  1. Normal branching
  2. Aberrant right subclavian artery origin
  3. Left circumflex aorta.



  Normal Branching Top


The normal left aortic arch develops when the hypothetical arch is interrupted distal to the right subclavian artery. The fourth branchial arch becomes the aortic arch, whereas portions of the third arch contribute to the head-and-neck arteries [Figure 3]a and [Figure 3]b. The order of the branches, from right to left, is as follows: the brachiocephalic artery that branches into right subclavian and right common carotid arteries, the left common carotid artery, and finally the left subclavian artery. The diameter of the brachiocephalic artery is larger than the left common carotid and subclavian arteries. The typical arch branching pattern occurs in 70%–80% of the population.
Figure 3: (a and b) A normal left aortic arch. (a) Black-shaded area represents the position of the break in a hypothetical arch. Arrows point to great vessels, right ductus arteriosus, and left ductus arteriosus. (b) Subsequently, the residual right arch becomes the brachiocephalic trunk that gives rise to the common carotid and right subclavian arteries. The persistent left arch gives rise to the left common carotid and subclavian arteries. BA Indicates brachiocephalic artery, LAA: Left aortic arch, LCCA: Left common carotid artery, LDA: Left ductus arteriosus, LPA: Left pulmonary artery, LSA: Left subclavian artery, RCCA: Right common carotid artery, RDA: Right ductus arteriosus, RPA: Right pulmonary artery, RSA, right subclavian artery

Click here to view


The most common arch variant branching pattern results from a common origin of the left common carotid artery and right brachiocephalic artery, or, less commonly, with the left common carotid arising directly from the right brachiocephalic artery. This pattern prevalence is estimated at 13% and 9%, respectively. Although typically referred to as a bovine-type arch, it is an incorrect term and should be avoided.[4] Another relatively common variant arch anatomy includes the left vertebral artery arising directly from the aortic arch with a prevalence of 5%–6%[5] [Figure 4].
Figure 4: Common arch branching variants patterns. (1) Right brachiocephalic artery; (2) left common carotid artery; (3) left subclavian artery; (4) right common carotid artery; (5) left vertebral artery

Click here to view


Transthoracic echocardiographic imaging technique for aorta

[Figure 5] shows schematically the four approaches to the aorta that were part of each examination. The ascending aorta was imaged from parasternal, subcostal, and suprasternal views. The examination of the ascending aorta required scanning to the left and the right from the standard suprasternal view [Figure 6]. With the orientation of the transducer toward the right shoulder of the patient, the normally positioned right innominate artery with the branching of the right subclavian artery and right carotid arteries could be seen [compare [Figure 7] with [Figure 5]]. This also aid in identifying the aortic arch as right or left sided. In this scan, the descending aorta could sometimes be visualized as well. Aortic arch branching was evaluated from suprasternal scans.
Figure 5: A segmental approach to the diagnosis of abnormalities of the aorta on transthoracic echo. The ascending aorta can be seen from parasternal, suprasternal, and subcostal scans, the aortic arch on multiple suprasternal scans, the aortic isthmus from suprasternal and high parasternal scans, and the descending aorta from parasternal and subcostal scans

Click here to view
Figure 6: Suprasternal long-axis echo view with probe pointer towards left shoulder of patient showing normal brachiocephalic branching in a left aortic arch. AAo: Ascending aorta, DAo: Descending aorta, LCC: Left common carotid artery, LSA: Left subclavian artery, RIA: Right Innominate artery, RPA: Right pulmonary artery

Click here to view
Figure 7: Modified suprasternal short axis echo view showing bifurcation of right innominate artery into. RSA: Right subclavian artery, RCA: Right common carotid artery, RIA: Right inominate artery

Click here to view


The aortic isthmus was visualized from suprasternal and high parasternal scans. It was necessary to obtain a view in which the main pulmonary artery (PA), left PA, and descending aorta was visualized simultaneously. This view [Figure 8] was entirely out of the plane of the ascending aorta and aortic arch branches, although occasionally the left subclavian artery was visualized. From this position, the region of the ductus arteriosus could be evaluated. Care was necessary to avoid confusing the normal crossing of the left PA and descending aorta with the ductus arteriosus.
Figure 8: High parasternal modified ductal echo view for aortic isthmus. R: Right, L: Left

Click here to view


The descending aorta was visualized from parasternal and subcostal views and its position was localized with respect to the spine to allow detection of a right-sided descending aorta In patients with a RAA the usual transition from a right-sided upper descending aorta to a left-sided lower descending aorta takes place at the region of the diaphragm and this could be traced in all [Figure 9]. Note was made of the pulsatility of the descending aorta in patients suspected of having aortic obstruction. Once an abnormality of the aorta was detected, it was necessary to continue to pursue a segmental approach to exclude the possibility of multiple aortic abnormalities.[6]
Figure 9: Subcostal long axis echo view of the descending aorta and the superior mesenteric artery. DAo: Descending aorta

Click here to view



  Left Aortic Arch with Aberrant Right Subclavian Artery Top


This is the most common congenital anomaly of the aortic arch with a prevalence of 0.5%–2%.[7] It occurs when there is a break in the primitive right arch between the right common carotid and subclavian arteries. Thus, the ARSA is the last aortic arch branch, a branch that travels from the left aortic arch, behind the esophagus, to perfuse the right upper extremity [Figure 10]a and [Figure 10]b and [Figure 11]. Most cases are asymptomatic, but in approximately 10% of adult patients may have dysphagia symptoms resulting from dilation, calcification, and hardening of the aberrant subclavian artery against the esophagus and commonly referred to as dysphagia lusoria.
Figure10: (a and b) The left aortic arch with ARSA. (a) Black-shaded area represents the position of the break in a hypothetical arch. Arrows point to great vessels, ductus arteriosus, and left ductus arteriosus. (b) Schematic representation of the evolution of the left arch and ARSA (arrow). Arrows point to arch vessels. LCCA: Indicates left common carotid artery, LDA: Left ductus arteriosus, LPA: Left pulmonary artery, LSA: Left subclavian artery, RCCA: Right common carotid artery, RDA: Right ductus arteriosus, RPA: Right pulmonary artery, RSA: Right subclavian artery, ARSA: Anomalous right subclavian artery

Click here to view
Figure 11: Suprasternal short axis (modified) view showing 1st arch branch is not bifurcating (right common carotid-RCCA). Another artery is seen below which is arising as last branch of arch and continuing as right subclavian artery (RSA)

Click here to view


A diverticulum of Kommerell, also referred to as a retroesophageal diverticulum, occurs in 15-30% cases when the ARSA arises from a diverticular outpouching of the thoracic aorta[8] [Figure 12]. The diverticulum is thought to represent a remnant of the right dorsal aorta related to the persistence of the right sixth arch dorsal portion (right ductus), which normally involutes. A vascular ring is completed by the right-sided ductus or ligamentum arteriosum. The presence of a retro esophageal diverticulum should suggest a ductus or ligamentum arteriosum on the contralateral side of the aortic arch and therefore completes a vascular ring that is commonly loose. If no retroesophageal diverticulum is present, the ductus or ligamentum arteriosum is on the same side of the aortic arch.
Figure 12: Kommerell diverticulum. ARSA: Aberrant right subclavian artery, LSA: Left subclavian artery, LCCA: Left common carotid artery, RCCA: Right common carotid artery

Click here to view


Patients with this anomaly occasionally have associated congenital abnormalities such as hypoplastic left heart syndrome, coarctation of the aorta, and atrioventricular canal defects. Aortic pathologies such as aneurysms, dissections, and arch branching abnormalities have been reported with ARSA. Patients with trisomy 21 have a high prevalence of this arch anomaly, reported to be 35%.[9] This anomaly is usually found incidentally, with treatment not required in asymptomatic patients. Occasionally, the aortic diverticulum of the Kommerell becomes aneurysmal and may require surgical resection.


  Right Aortic Arch Top


The RAA has a reported prevalence in adults of 0.04% to 0.1%, based on a necropsy series. The RAA results from dissolution of the left dorsal aortic root instead of the right dorsal root [Figure 13]a and [Figure 13]b and [Figure 14]. The RAA anomaly can be associated with congenital cardiac anomalies, esophageal atresia, and tracheoesophageal fistula.
Figure 13: (a and b) RAA with mirror image branching. (a) Black-shaded area represents the position of the break in a hypothetical arch. (b) Schematic representation of the evolution of the right arch and mirror image branching. Arrows point to great vessels and ductus arteriosus. BA: Indicates brachiocephalic artery, LCCA: Left common carotid artery, LDA: Left ductus arteriosus, LPA: Left pulmonary artery, LSA: Left subclavian artery, RCCA: Right common carotid artery, RDA: Right ductus arteriosus, RPA: Right pulmonary artery, RSA: Right subclavian artery, RAA: Right aortic arch

Click here to view
Figure14: Supra-sternal view with echo transducer rotated clockwise and pointer at 5 o'clock position. Left panel in two-dimensional and right panel in colour Doppler. AAo: Ascending aorta, DAo: Descending aorta

Click here to view


The most common classification scheme identifies three main subgroups of the RAA as follows:

  1. RAA with mirror image branching
  2. RAA with an aberrant left subclavian artery (ALSA)
  3. RAA with the isolation of the left subclavian artery.


An uncommon variant of the RAA, the “circumflex retroesophageal aorta” occurs when the RAA crosses the midline posterior to the esophagus before descending on the contralateral side, resulting in the ascending and descending aorta on opposite sides of the thoracic vertebrae.[3]


  Right Aortic Arch with Mirror Image Branching Top


This is the second-most common form of right arch anomaly after the right arch with ALSA. It results from partial regression of the left fourth arch after the origin of the left subclavian artery (seventh intersegmental branch). The arch branching is typically the left brachiocephalic artery, followed by right common carotid and, last, the right subclavian artery [Figure 15] and [Figure 16]. The descending aorta is on the right, and the ductus is present on the left (75% of these cases). In almost all cases, the involution occurs between the left ductus and the dorsal descending aorta, and characteristically, the left sixth arch persists as a ductus or ligamentum arteriosum between the left brachiocephalic artery anteriorly and the left PA posteriorly. There is no vascular ring formation but is strongly associated with CHD, including tetralogy of Fallot, truncus arteriosus, tricuspid atresia, and transposition of great artery with pulmonary valve stenosis. The differential includes a double aortic arch with atretic left arch, although in this situation the descending aorta is usually left sided.
Figure 15: Suprasternal echo view: Right aortic arch. The first brachiocephalic branch off the aortic arch courses leftward (arrow). Ao: Aorta

Click here to view
Figure 16: Suprasternal scan obtained with transducer aimed toward the left shoulder of the patient showing mirror image branching of a right aortic arch with visualization of the left carotid (LCA) and left subclavian arteries (LSA) from left Innominate Artery (LIA). Ao: Aorta

Click here to view


In very rare cases and typically not associated with CHD, the involution occurs between the left subclavian artery and the left ductus, resulting in a RAA with mirror image branching but with a left ductus connecting a retroesophageal diverticulum and the PA and completing a vascular ring. In approximately 25% cases the ductus is located on the right, the result of left sixth arch regression with the persistence of the right sixth arch with the actual mirror image of the normal left arch anatomy. This is not associated with a vascular ring or intra-cardiac defect. Occasionally, the ductus is bilateral and may or may not be associated with the cardiac anomaly. An absent ductus is associated with major intra-cardiac anomaly.[10]


  Right Aortic Arch with an Aberrant Left Subclavian Artery Top


RAA with ALSA is the most common variation of a RAA. This anomaly results from the regression of the left fourth arch between the left common carotid and left subclavian arteries, usually with the persistence of the left sixth arch [Figure 17]a and [Figure 17]b and [Figure 18]. The ALSA is the last arch branch, and typically has an oblique retroesophageal course from caudal right to cranial left. A portion of the left dorsal aorta typically persists as a retroesophageal diverticulum, giving rise to the aberrant subclavian artery. RAA with ALSA arising from a retroesophageal diverticulum of Kommerell is the second most common cause of a vascular ring after a double aortic arch. The vascular ring is often relatively loose and is completed by a patent left ductus arteriosus or ligamentum arteriosum, which typically attaches between the left PA and the retroesophageal diverticulum. This anomaly is rarely associated with CHD.
Figure 17: (a and b) RAA with an ALSA. (a) Black-shaded area represents the position of the break in double aortic arch. (b) Schematic representation of the evolution of the right arch and ALSA. Arrows point to great vessels and ductus arteriosus. LCCA indicates left common carotid artery, LDA: Left ductus arteriosus, LPA: Left pulmonary artery, RCCA: Right common carotid artery, RPA: Right pulmonary artery, RSA: Right subclavian artery, RAA: Right aortic arch, ALSA: Anomalous left subclavian artery

Click here to view
Figure 18: Suprasternal scan of the right-sided descending aorta (DAo) and the anomalous origin of the LSA (arrow). LSA: Left subclavian artery

Click here to view


Less commonly, a RAA can be accompanied by an ALSA in the absence of a retroesophageal diverticulum. This anomaly results from the regression of the left fourth and left sixth arches, and therefore the left dorsal aorta does not contribute to the descending aorta. In contrast with patients with a retroesophageal diverticulum, the ductus arteriosus is absent or is right-sided and therefore does not form a vascular ring. Unlike a RAA with ALSA arising from a diverticulum of Kommerell, this particular arch anomaly usually occurs in the presence of conotruncal abnormalities such as Tetralogy of Fallot or truncus arteriosus.

Early surgical treatment of the Kommerell diverticulum is recommended because of the risk of potential aneurysm rupture. Surgery entails resection of the diverticulum and reimplantation of the ALSA into the aorta by means of left thoracotomy.[3]


  Right Arch with Isolation of the Left Subclavian Artery Top


Isolation refers to an arch vessel arising typically from the PA through a ductus arteriosus and without communication to the aorta. The most common form is a RAA with the isolation of the left subclavian artery and is associated with CHD in 50% of cases. It results from involution of the left arch at two separate segments, between the left common carotid and left subclavian arteries, and between the left ductus arteriosus and left subclavian artery [Figure 19]a and [Figure 19]b. If the ductus arteriosus closes, this anomaly may result in subclavian steal phenomenon with subsequent vertebrobasilar insufficiency. Surgical correction of the isolated subclavian artery may be performed at the same time as corrective surgery for associated CHD. In patients with no CHD, left carotid subclavian bypass may alleviate the symptoms related to vertebral steal phenomenon.[3]
Figure 19: (a and b) RAA with isolation of LSA. (a) Black-shaded areas represent positions of breaks in a hypothetical arch. (b) Schematic representation of the evolution of the right arch and ILSA. Arrows point to great vessels and ductus arteriosus. ILSA indicates isolated left subclavian artery, LCCA: Left common carotid artery, LDA: Left ductus arteriosus, LPA: Left pulmonary artery, RCCA: Right common carotid artery, RDA: Right ductus arteriosus, RPA: Right pulmonary artery, RAA: Right aortic arch, LSA: Left subclavian artery

Click here to view



  Double Aortic Arch Top


Double aortic arch is the most common cause of a symptomatic vascular ring and accounts for 50%–60% of vascular rings. When symptomatic during infancy or childhood, it characteristically presents with respiratory symptoms or feeding difficulties. However, it is not uncommon to see asymptomatic adults. It results from lack of involution of the right and left fourth arches and the right and left dorsal aortae, each giving rise to a separate common carotid and subclavian arteries [Figure 20]. Usually, only 1 of the 2 sixth arches persist, giving rise to a ductus or ligamentum arteriosum. This anomaly is rarely associated with CHD. Approximately 20% of patients with a double aortic arch anomaly have associated chromosomal abnormalities.[10]
Figure 20: Embryology of a double aortic arch. The diagram shows a double aortic arch with ductus arteriosus on each side. There are no breaks in the primitive double arch. LCCA: Indicates left common carotid artery, LDA: Left ductus arteriosus, LPA: Left pulmonary artery, LSA: Left subclavian artery, RCCA: Right common carotid artery, RDA: Right ductus arteriosus, RPA: Right pulmonary artery, RSA: Right subclavian artery

Click here to view


Generally, the proximal aorta bifurcation into right and left arches is higher than the level of distal confluence of the arches. The right arch is commonly larger and higher than the left arch (55%–70% of cases). Less commonly, the left arch is dominant (20%–35%). In a minority, both arches are equal in size (5%–10%). The descending aorta is typically located on the left and classically opposite to the dominant arch, but may be seen on the right or midline. The ductus arteriosum is commonly located on the left, but may be present on the right or rarely be bilateral. The smaller arch may be focally or diffusely stenotic or atretic, more commonly the left arch.

Two scenarios are possible with a partially atretic left arch. In one, the atretic segment is present between the left common carotid and left subclavian artery and mimics a right arch with ALSA from a retroesophageal diverticulum.

In another possibility, a more distal atretic segment beyond the left subclavian artery can be confused with a right arch with mirror image branching. It is important to differentiate these entities as double aortic arches even when atretic segments constitute actual vascular rings while RAAs with mirror branch imaging commonly do not. Findings that suggest an atretic arch include the symmetric appearance of the bilateral common carotid and subclavian arteries originating from their respective ipsilateral arches on an axial image just above the level of the arches (the 4-vessel or 4 artery sign) [Figure 21]. In contrast, a right arch with mirror image branching, the left subclavian artery arises from the left brachiocephalic artery with significant asymmetry. In addition, it may be apparent tethering and distortion of the left common carotid or subclavian artery posteriorly from the patent aortic arch caused by traction from the atretic segment. Arch dominance determination has significant surgical consequences, as thoracotomy is usually performed in the non-dominant side.
Figure 21: Suprasternal notch imaging showing right aortic arch descending rightward (red arrow), smaller left aortic arch descending leftward (yellow arrow), and respective right (green arrow) and left (orange arrow) innominate arteries which will branch into common carotid and subclavian arteries

Click here to view


Coronal multiplanar reformat and three-dimensional volume-rendered images are particularly useful. In apparently equal-sized aortic arches, one of the arches typically gets smaller in the posterior aspect near the descending aorta. It is also important to remind the surgeon that an apparent RAA with retroesophageal diverticulum or RAA with left descending aorta could be an atretic left aortic arch in addition to a left ligament.

The treatment of symptomatic patients with a double aortic arch is surgical correction with the division of the vascular ring to relieve compression of the trachea and esophagus. The long-term prognosis for patients with a repaired, uncomplicated double aortic arch is excellent.


  Persistent Fifth Aortic Arch Top


The primitive fifth aortic arches are rudimentary vessels that quickly degenerate in approximately half of the embryos, whereas in others these arteries do not develop at all. However, rarely, a primitive fifth arch may persist, located below the fourth arch [Figure 22]. This anomaly is usually associated with intra-cardiac malformations, most commonly VSD. Persistent fifth aortic arch is considered a rare anomaly. However, following review of more than 2000 specimens, Gerlis et al. concluded that persistence of a fifth aortic arch may not be as rare as commonly perceived, as it is often misdiagnosed.[11] This anomaly is most frequently mistaken for a ductus arteriosus or aorto-pulmonary window. A persistent fifth arch can connect the ascending aorta to the descending aorta (systemic-to-systemic connection) or the ascending aorta to a derivative of the sixth arch, usually, the left PA (systemic-to-pulmonary connection) [Figure 23]. The clinical presentation of this anomaly depends on which of these anatomic connections exists and on associated cardiovascular anomalies.[12]
Figure 22: Persistent fifth aortic arch

Click here to view
Figure 23: Transthoracic echocardiogram in suprasternal long axis view shows left-sided aortic arch with normal branching pattern of neck vessels. A vascular channel (*) originates unequivocally proximal to the origin of the right brachiocephalic artery and terminates at the pulmonary artery confluence. The pulmonary end of this vascular channel is constricted with turbulence seen on color Doppler interrogation (right panel). AAo: Ascending aorta, BCA: Brachiocephalic artery, CCA: Common carotid artery, RPA: Right pulmonary artery, SCA: Subclavian artery

Click here to view



  Interrupted Aortic Arch Top


IAA refers to the focal discontinuity between the ascending and descending thoracic aorta with flow to the descending aorta dependent on a patent ductus arteriosus. The separation can be complete or fibrous tissue cord may be present. IAA prevalence is estimated at 2/100,000 live births. There is a significant association with patients with Di George syndrome who present an IAA in 5%–20% of cases, whereas 40%–50% with IAA will have Di George syndrome.

The most commonly used classification system recognizes three groups: Type A, distal to the left subclavian artery; Type B, distal to the left common carotid artery takeoff; and Type C, proximal to the origin of the left common carotid artery [Figure 24]. Type B accounts for 50%–60% of cases [Figure 25] and [Figure 26], Type A represents 30%–40% of cases, and Type C is the least common (<5% of cases). In any of these types, the right subclavian artery may demonstrate a normal origin (subtype 1) or anomalous origin (distal to the left subclavian artery, subtype 2; or from the right ductus arteriosus, subtype 3). IAA is commonly associated with large ventricular septal defect (VSD) and left ventricular outflow obstruction. Less commonly, it may present with a large aorto-pulmonary window or truncus anomaly.
Figure 24: Celoria and Patton classification of Interrupted aortic arch

Click here to view
Figure 25: Interrupted aortic arch Type B. Suprasternal long-axis image demonstrates the innominate artery (asterisk) and left common carotid artery (double asterisk) arising from the aortic arch. The left subclavian artery arises distal to the interruption from the descending aorta

Click here to view
Figure 26: High para-sternal short axis view of the same case as in [Figure 25], showing large PDA continuing as descending aorta. LPA: Left pulmonary artery, PDA: Patent ductus arteriosus

Click here to view


Patients present in the first 2 weeks of life with shock or severe heart failure after spontaneous closure of the ductus arteriosum. On physical examination, a gray appearance of the lower body due to hypoperfusion is characteristic with the difference in systolic blood pressure and oxygen saturation between the right upper extremity and lower extremities. IAA is usually treated with side-to-side anastomosis rather than conduit interposition.[10]


  Aortic Hypoplasia Top


Hypoplasia of the aorta refers to an abnormally diffuse reduced caliber of the aorta that commonly results in obstruction to the antegrade flow. Narrowing may involve the entire aortic arch or a limited portion. It could be defined based on reference standards adjusted to body mass index (>2 Z score). In the presence of a normal ascending aorta, proximal arch, distal arch, and isthmus hypoplasia can be diagnosed if their diameters are < 60%, 50%, or 40% compared with the ascending aorta, respectively [Figure 27]. Aortic arch hypoplasia can be an isolated finding or be associated with other obstruction left-sided lesions, such as congenital mitral stenosis, mitral atresia, hypoplastic left heart syndrome, aortic stenosis, aortic atresia, IAA, and coarctation of the aorta. Treatment is typically considered for a hemodynamically significant lesion with a gradient > 15–20 mm Hg.[10]
Figure 27: Echocardiographic findings in a case of moderate aortic coarctation and hypoplasia of the arch. Left panel: Two-dimensional echocardiographic view of the aortic arch shows a moderate aortic coarctation (arrow). Left panel: Color Doppler image showing turbulence in the arch due to the coarctation. AAO: Ascending aorta, DAO: Descending aorta.

Click here to view



  Coarctation of the Aorta Top


Coarctation of the aorta characteristically refers to the focal narrowing of the aorta usually near the ligamentum arteriosum distal to the left subclavian artery [Figure 28]a, [Figure 28]b and [Figure 29]a, [Figure 29]b. It accounts for 7% of all CHD with a prevalence of 4/10,000 live births. Diagnosis can be easily made in infants and young children by Echo only, however, in grown up children and adult CT Aortogram is required to delineate the anatomy.
Figure 28: (a) Suprasternal echo view showing discrete coarctation (depicted by two arrows) of descending aorta distal to left subclavian artery in two-dimensional and colour Doppler. (b) Continuous wave Doppler across the arch showing the gradient across the narrowing and diastolic run-off indicating the severity of the coarctation

Click here to view
Figure 29: (a and b) Sub-xiphoid echo view in two-dimensional demonstration the descending aorta and in pulse wave Doppler showing dampened flow with diastolic spill

Click here to view


It may occur as an isolated lesion in approximately 80% of cases. It is commonly associated with Turner syndrome, bicuspid aortic valve, intracranial aneurysms, VSD, atrial septal defect, and Shone complex (left ventricular outflow obstruction and parachute mitral valve).

However, coarctation is only very rarely associated with RAAs, with a reported prevalence of only 0.1%. In patients with coarctation of a right arch, the majority have RAA with ALSA. In this setting, coarctation tends to manifest as a hypoplastic segment of the aorta between the right and left subclavian arteries, which has been postulated to be a relatively low-flow region in the setting of normally distributed left and right ventricular outflows.

Typically, patients present with arterial hypertension in the upper extremities and a systolic murmur. Characteristic findings included focal eccentric narrowing of the juxtaductal thoracic aorta with multiple collateral vessels bypassing the stenotic segment. Coarctation of the aorta can be treated surgically with tube grafts or aortoplasty, percutaneous balloon angioplasty, and stent placement.[13]


  Pseudocoarctation Top


Pseudocoarctation is a rare anomaly consisting of kinking and buckling of the arch and descending aorta at the level of the ligamentum arteriosum [Figure 30]. There is no actual pressure gradient across the stenosis, and therefore the lesion is not hemodynamically significant with no collateral vessel formation. Patients are classically asymptomatic, and it is considered a benign anomaly that generally requires no surgical intervention. Occasionally, symptomatic patients and those with aneurysmal formation may require treatment. The pathogenesis of aneurysm beyond the kinked segment may relate to abnormal turbulent flow.[13]
Figure 30: Pseudocoarctation demonstrated by three-dimensional reconstruction of computed tomography aortogram

Click here to view


Pulmonary artery anomalies

We will be discussing few anomalies of PA origin and bifurcation like PA sling which has clinical presentation similar to the vascular ring and anomalous origin of PA from aorta which presents as large aortopulmonary communication with congestive heart failure.


  Pulmonary Artery Sling Top


A PA sling is an anomalous origin of the left PA from the right PA with a course between the trachea and esophagus. Presenting symptoms, often during the neonatal period or infancy, include stridor, respiratory distress, and recurrent respiratory infection. A Type I sling is just above the carina at T4-5 level and is usually associated with a normal trachea. Type II slings are located more caudally adjacent to a low T-shaped carina at T5-6 level and often have long-segment tracheal stenosis due to complete cartilaginous tracheal rings, resulting in an O-shaped trachea with absent pars membranacea. Because the tracheal obstruction is primary and not just by extrinsic compression, the surgical treatment involves tracheoplasty in addition to addressing the vascular abnormality. Echo can detect this defect in most of the cases in children [Figure 31].[14],[15]
Figure 31: Transthoracic echocardiogram showing main pulmonary artery giving rise to right pulmonary artery with arrow depicting left pulmonary artery arising from its distal segment. Doppler showing main pulmonary artery, right pulmonary artery and left pulmonary artery flow. Note turbulence within the left pulmonary artery segment as it courses between the trachea and esophagus

Click here to view



  Anomalous Origin of the Left or Right Pulmonary Artery From Aorta Top


Anomalous origin of either the right or left PA from the ascending aorta is a rare malformation, with the former being more common. These lesions should be differentiated from discontinuous pulmonary arteries, where one of the branches is supplied by an arterial duct. The lesion has been called hemi-truncus, though this is a misnomer because there are two semilunar valves, rather than the common truncal valve necessary to diagnose common arterial trunk.

There is frequently associated intra-cardiac disease, most commonly a VSD which may exacerbate the problem. The anomalous PA acts as a very large aortopulmonary collateral, shunting much of the oxygenated blood back to the lungs and creating a volume load to the left heart. It also exposes the pulmonary vascular bed to systemic arterial pressures, resulting in severe pulmonary vascular obstructive disease if uncorrected. Patients may present with tachypnea, failure to gain weight appropriately, respiratory distress, and congestive heart failure. Survival has been reported as low as 30% at 1 year of age if untreated. Diagnosis can be made on echocardiography [Figure 32], CT, or MRI. The diagnosis alone is an indication for surgical intervention. Surgical treatment includes the reimplantation of the PA to the pulmonary trunk. Outcome after the early intervention is reported to be good, though surgical or percutaneous re-intervention to address aortic or pulmonary stenosis is not uncommon.[16]
Figure 32: Right parasternal short axis view showing right pulmonary artery arising from ascending aorta in two-dimensional echo (on right) and color Doppler images (on left). Main pulmonary artery continuing as left pulmonary artery. MPA: Main pulmonary artery, LPA: Left pulmonary artery, RPA: Right pulmonary artery, AAo: Ascending aorta

Click here to view


Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

 
  References Top

1.
Momma K, Matsuoka R, Takao A. Aortic arch anomalies associated with chromosome 22q11 deletion (CATCH 22). Pediatr Cardiol 1999;20:97-102.  Back to cited text no. 1
    
2.
Bogren HG, Porter BA. Three aortic arch anomalies: A review of the literature and proposal of a new classification. Cardiovasc Intervent Radiol 1980;3:19-23.  Back to cited text no. 2
    
3.
Stojanovska J, Cascade PN, Chong S, Quint LE, Sundaram B. Embryology and imaging review of aortic arch anomalies. J Thorac Imaging 2012;27:73-84.  Back to cited text no. 3
    
4.
Layton KF, Kallmes DF, Cloft HJ, Lindell EP, Cox VS. Bovine aortic arch variant in humans: Clarification of a common misnomer. AJNR Am J Neuroradiol 2006;27:1541-2.  Back to cited text no. 4
    
5.
Jakanani GC, Adair W. Frequency of variations in aortic arch anatomy depicted on multidetector CT. Clin Radiol 2010;65:481-7.  Back to cited text no. 5
    
6.
Huhta JC, Gutgesell HP, Latson LA, Huffines FD. Two-dimensional echocardiographic assessment of the aorta in infants and children with congenital heart disease. Circulation 1984;70:417-24.  Back to cited text no. 6
    
7.
Türkvatan A, Büyükbayraktar FG, Olçer T, Cumhur T. Congenital anomalies of the aortic arch: Evaluation with the use of multidetector computed tomography. Korean J Radiol 2009;10:176-84.  Back to cited text no. 7
    
8.
Poterucha J,Anavekar N, Niaz T, Agarwal A, Young P, Dearani J, et al. Incidence and clinical presentation of Kommerell diverticulum. J Am Coll Cardiol. 2015;65 (10_Supplement):A524.  Back to cited text no. 8
    
9.
Fehmi Yazıcıoğlu H, Sevket O, Akın H, Aygün M, Özyurt ON, Karahasanoğlu A. Aberrant right subclavian artery in Down syndrome fetuses. Prenat Diagn 2013;33:209-13.  Back to cited text no. 9
    
10.
Landeras LA, Chung JH. Congenital thoracic aortic disease. Radiol Clin North Am 2019;57:113-25.  Back to cited text no. 10
    
11.
Gerlis LM, Ho SY, Anderson RH, Da Costa P. Persistent 5th aortic arch A great pretender: Three new covert cases. Int J Cardiol 1989;23:239-47.  Back to cited text no. 11
    
12.
Gupta SK, Gulati GS, Anderson RH. Clarifying the anatomy of the fifth arch artery. Ann Pediatr Cardiol 2016;9:62-7.  Back to cited text no. 12
    
13.
Hanneman K, Newman B, Chan F. Congenital variants and anomalies of the aortic arch. Radiographics 2017;37:32-51.  Back to cited text no. 13
    
14.
Bryant R, Yoo SJ. Vascular rings, pulmonary arterial sling, and related conditions. Andersons Pediatr Cardiol 2019;47:877-900.e4.  Back to cited text no. 14
    
15.
Healey D, Ron N, Hromada A, Chhabra M. Perinatal/Neonatal case presentation: Pulmonary artery sling associated with respiratory distress. Springerplus 2016;5:1656-5.  Back to cited text no. 15
    
16.
Goldstein BH, Bergersen L, Powell AJ, Graham DA, Bacha EA, Lang P. Long-term outcome of surgically repaired unilateral anomalous pulmonary artery origin. Pediatr Cardiol 2010;31:944-51.  Back to cited text no. 16
    


    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8], [Figure 9], [Figure 10], [Figure 11], [Figure 12], [Figure 13], [Figure 14], [Figure 15], [Figure 16], [Figure 17], [Figure 18], [Figure 19], [Figure 20], [Figure 21], [Figure 22], [Figure 23], [Figure 24], [Figure 25], [Figure 26], [Figure 27], [Figure 28], [Figure 29], [Figure 30], [Figure 31], [Figure 32]



 

Top
 
 
  Search
 
Similar in PUBMED
   Search Pubmed for
   Search in Google Scholar for
 Related articles
Access Statistics
Email Alert *
Add to My List *
* Registration required (free)

 
  In this article
Abstract
Introduction
Embryology
Classification o...
Left Aortic Arch...
Normal Branching
Left Aortic Arch...
Right Aortic Arch
Right Aortic Arc...
Right Aortic Arc...
Right Arch with ...
Double Aortic Arch
Persistent Fifth...
Interrupted Aort...
Aortic Hypoplasia
Coarctation of t...
Pseudocoarctation
Pulmonary Artery...
Anomalous Origin...
References
Article Figures

 Article Access Statistics
    Viewed570    
    Printed4    
    Emailed0    
    PDF Downloaded117    
    Comments [Add]    

Recommend this journal


[TAG2]
[TAG3]
[TAG4]