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Fetal Aortic Arch Anomalies
Key Sonographic Views for Their Differential Diagnosis and
Clinical Implications Using the Cardiovascular System
Sonographic Evaluation Protocol
ortic arch anomalies refer to a variety of congenital abnormal-
ities that are related to the position or branching of the aortic
arch, which occur in 1% to 2% of the general population.
1,2
Most of these anomalies (up to 50%) have been reported to be asso-
ciated with congenital heart disease, which means that isolated
vascular rings are uncommon (1–1.6 per 1000 pregnancies).
3–5
The most common type of aortic arch anomaly is a left aortic arch
with an aberrant right subclavian artery, followed by a right aortic
arch anomaly with an aberrant left subclavian artery, a right aortic
arch anomaly with mirror image branching, and a double aortic arch
anomaly.
5–8
Although most aortic arch anomalies are clinically unimpor-
tant in the neonate, during fetal life, they serve as markers for fetal
congenital heart disease and chromosomal defects, including 22q11
microdeletion.
9
The presence of an aberrant subclavian artery,
either right or left, regardless the laterality of the aortic arch, has
been associated with an increased incidence of chromosomal abnor-
malities, mainly when other associated anomalies are detected.
Thus, its prenatal detection is particularly relevant.
10
Over the last 30 years, we have witnessed an evolution in the
prenatal assessment of the fetal heart and great vessels using various
methods, with a common trend being the progressive addition of
complementary views, starting with the basic 4-chamber view up to
the 5 axial views, which can provide a wider image and can give us a
Coral Bravo, MD, PhD, Francisco Gámez, MD, PhD, Ricardo Pérez, MD, PhD, Teresa Álvarez, MD,
Juan De León-Luis, MD, PhD
Received February 25, 2015, from the Depart-
ments of Obstetrics and Gynecology (C.B.A., F.G.,
R.P., J.D.L.-L.) and Pediatric Cardiology (T.Á.),
Hospital General Gregorio Marañón, Universidad
Complutense de Madrid, Madrid, Spain; and
Department of Obstetrics and Gynecology,
Hospital Central de la Defensa Gómez Ulla,
Universidad de Alcalá de Henares, Madrid, Spain
(C.B.A.). Revision requested April 3, 2015.
Revised manuscript accepted for publication May
23, 2015.
We thank Anne Marie Palma for assistance
with manuscript preparation. This work was
supported by the Fondo de Investigaciones
Sanitarias (grant FIS PI13-02769).
Address correspondence to Juan De León-
Luis, MD, PhD, Fetal Medicine Unit, Department
of Obstetrics and Gynecology, Hospital General
Universitario Gregorio Marañón, Calle O’Donnell
48, Planta 0, Bloque C, 28009 Madrid, Spain.
E-mail: jdeleonluis@yahoo.es
A
©2016 by the American Institute of Ultrasound in Medicine | J Ultrasound Med 2016; 35:237–251 | 0278-4297 | www.aium.org
REVIEW ARTICLE
Aortic arch anomalies are present in 1% to 2% of the general population and are com-
monly associated with congenital heart disease, chromosomal defects, and trachea-
esophageal compression in postnatal life. The sonographically based detection of aortic
arch anomalies lies in the 3-vessel and trachea view. Although highly sensitive, this view
alone does not allow identification of the aortic arch branching pattern, which prevents
an accurate diagnosis. The systematic addition of a subclavian artery view as part of a
standardized procedure may be useful in the differential diagnosis of these conditions.
We describe the sonographic assessment of fetal aortic arch anomalies by combining 2
fetal transverse views: the 3-vessel and trachea view and the subclavian artery view, which
are included in the cardiovascular system sonographic evaluation protocol. We also review
the sonographic findings and the clinical implications of fetal aortic arch anomalies.
Key Words—aberrant subclavian artery; aortic arch anomalies; double aortic arch;
echocardiography; prenatal diagnosis; right aortic arch; subclavian artery view; 3-vessel
and trachea view
doi:10.7863/ultra.15.02063
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greater understanding of the anomalies in this area.
11–14
Although at the beginning, sonographers were reticent
about the addition of further views, they have been gradu-
ally incorporating these improvements based on the better
results obtained in terms of diagnosis.
15
In this progressive
development, the axial view has been the most representative
in every systematic approach. Prenatal evaluation of aortic
arch anatomy and its branching has been classically per-
formed by using the axial 3-vessel and trachea view.
13,16
Nevertheless, and on the basis of previous statements, we
are on the verge of extending our cardiovascular explo-
ration area by also including the cranial area to improve our
diagnostic capability by implementing the cardiovascular
system sonographic evaluation protocol.
17
Furthermore,
we have already reported that the addition of a subclavian
artery axial view to the usual 3-vessel and trachea view as
part of a standardized procedure may substantially con-
tribute to the characterization of aortic arch anomalies in
fetuses, using a simple method that can be easily added to
the conventional scanning procedure.
17
The aim of this article is to describe an improvement
made to the systematic method used for the sonographic
assessment of fetal aortic arch anomalies by combining
the findings of 2 fetal transverse views: the 3-vessel and
trachea view and the subclavian artery view (cardiovascu-
lar system sonographic evaluation protocol)
17
and to review
the sonographic findings and clinical implications of fetal
aortic arch anomalies.
Embryonic Development of the Aortic Arch
and Fetal Anatomy
In 1948, the pathologist Jesse E. Edwards introduced a
hypothetical model, which allowed the understanding
of normal and abnormal development of the aortic arch.
18,19
According to this model, most aortic arch anomalies can
be explained as disruptions of aortic arch formation.
20
Development of the aorta occurs during the third
week of gestation.
21
Each primitive aorta consists of a ven-
tral part and a dorsal part, connected by an arch. The 2
ventral aortas fuse to form the aortic sac, whereas the dor-
sal aortas fuse to form the midline descending aorta.
Between both, there are 6 pairs of aortic arches (Figure 1).
22
To simplify, 2 symmetric aortic arches form a vascular
ring around the trachea and esophagus, connecting the
ascending and descending aortas. Each aortic arch gives
rise to a common carotid artery and a subclavian artery.
On each side, right- and left-sided ducti arteriosi connect
the pulmonary arteries to the distal part of each aortic arch,
forming an additional vascular ring.
In normal development, the left aortic arch and left-
sided ductus arteriosus persist, whereas the right aortic arch,
distal to the origin of the right subclavian artery, and the
right-sided ductus arteriosus regress (Figure 2). As a result,
the proximal part of the embryologic right aortic arch remains
as the brachiocephalic artery, which bifurcates into the
right common carotid artery and the right subclavian artery.
The left-sided aortic arch, in turn, gives rise to the bra-
chiocephalic artery, left common carotid artery, and left
subclavian artery (Figure 2).
20
Aortic arch anomalies are usually caused by an abnor-
mal position of the arch or abnormal branching, due to the
persistence of areas that should have adequately regressed or
have regressed at an abnormal point (Figure 3). The assess-
ment and description of the anomalies, therefore, should
include the following: (1) the position of the aortic arch
relative to the trachea; (2) the location of the most proximal
part of the descending aorta in relation to the spine; (3) the
presence or absence of an aberrant branch; and (4) the ori-
gin and insertion of the ductus arteriosus.
20
Usefulness of Combining the 3-Vessel and
Trachea and Subclavian Artery Views
Included in the Cardiovascular System
Sonographic Evaluation Protocol
The fetal upper mediastinum is the area that should be
assessed in a sonographic study of fetal aortic arch anom-
alies. This area has been classically explored by using the 3-
vessel and trachea view.
13
In this cross-sectional view, the
pulmonary artery communicating with the ductus arterio-
sus is identified, and to its right, a transverse section of the
aortic arch, the superior vena cava, and a transverse section
of the trachea are shown (Figure 4). The aortic arch and the
ductus arteriosus are arranged in a V shape, which opens
toward the anterior chest wall and has its vertex to the left of
the trachea. On the right of the trachea, the azygos vein can
be observed in its posteroanterior course to the superior vena
cava. This view is useful for assessment of the great vessels;
however, it can be easily complemented to better establish
the branching pattern of the aortic arch and to characterize
various anomalies. To achieve this purpose, assessment of
the anatomic position of the subclavian arteries is essential.
The visualization of both normal fetal subclavian
arteries in a transverse section requires an upward swiping
motion to a plane slightly cranial to the 3-vessel and tra-
chea view.
23
The subclavian arteries are seen on either side
of the thorax as vessels with an origin anterior to the trachea
and an S-shaped course toward the fetal arm that resembles
a bicycle handlebar (Figure 4). To see these vessels, highly
Bravo et al—Sonographic Views of Fetal Aortic Arch Anomalies
J Ultrasound Med 2016; 35:237–251238
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sensitive color Doppler imaging with a low velocity range
(10–15 cm/s) is required, although a pulsed wave Doppler
interrogation is also useful for providing a classic arterial
waveform.
23
In the second-trimester scan, the frequency
with which these fetal structures can be seen in both views
reaches 99%.
17
The combined use of these axial views (3-vessel and
trachea and subclavian artery) helps determine the presence
of a retrotracheal vessel and, thus, a potential vascular ring
or sling. The absence of an aberrant subclavian artery in the
3-vessel and trachea view should be confirmed by the char-
acteristic handlebar shape of these arteries in the upper view.
The absence of this typical image should prompt a search
for an aberrant vessel in the 3-vessel and trachea view.
The subclavian artery view may help diminish false-positive
diagnoses given by the azygos vein and false-negative diag-
noses given by the innominate vein.
24
Complementarily, an aberrant subclavian artery,
either right or left, can also be confirmed by a coronal view
when the transverse images are not clear enough. This
view has the advantage of providing an image of the origin
and course of the anomalous artery in the same plane.
25
Anomalies of the Aortic Arch: Sonographic
Findings and Clinical Relevance
Anomalies of the aortic arch can be characterized on the
basis of the number and position of the vessels seen in
the 3-vessel and trachea view, in combination with the
sonographic findings in the subclavian artery view.
Aortic Arch Anomalies With 3 Vessels in
the 3-Vessel and Trachea View
Left Aortic Arch With an Aberrant Right Subclavian Artery
Embryologic Origin
A left aortic arch with an aberrant right subclavian artery is
the result of abnormal regression of the right aortic arch
between the origins of the right common carotid and right
subclavian arteries, leaving the right subclavian artery
attached to the distal remnant of the left-sided aortic arch
(Figure 3). In most cases, the left-sided ductus arteriosus
persists. This combination of vascular elements forms a
vascular sling around the left side of the trachea and esoph-
agus (Figure 3).
J Ultrasound Med 2016; 35:237–251 239
Bravo et al—Sonographic Views of Fetal Aortic Arch Anomalies
Figure 1. Embryonic development of the aortic arch and supra-aortic vessels. A, Embryo at 26 to 29 days. B, Embryo at 35 to 40 days. Between the
ventral and dorsal aorta, there are 6 pairs of aortic arches. The first 2 arches regress as the other arches form. The third aortic arch is responsible for
the formation of the carotid arteries. The left arch of the fourth pair forms the segment of the normal left aortic arch, which is located between the left
common carotid and subclavian arteries. The fourth right arch forms the proximal right subclavian artery. The distal right subclavian artery is derived
from a portion of the right dorsal aorta and the seventh right intersegmental artery. The left arch of the sixth pair contributes to the formation of the
main and left pulmonary arteries and ductus arteriosus. The sixth right arch contributes to the formation of the right pulmonary artery. The left sub-
clavian artery is derived entirely from the seventh left intersegmental artery, whereas portions of the right artery are derived from the fourth right arch
and the right dorsal aorta. CNS indicates central nervous system.
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Sonographic Findings
In this case, the 3-vessel and trachea view shows the normal
anatomic appearance of the great vessels: the left-sided
ductus arteriosus and the transverse portion of the aortic
arch forming a V-shaped structure on the left of the tra-
chea and a transverse section of the superior vena cava
(Figure 5A). This image is subsequently modified at the
level of the aortic isthmus due to the presence of an aberrant
vessel, the aberrant right subclavian artery, which crosses
the fetal chest posterior to the trachea toward the right
upper limb (Figure 5A).
When moving upward to the subclavian artery view,
the proximal origin and antetracheal course of the normal
right subclavian artery are not visible. The distal portion of
the aberrant right subclavian artery might be seen close
to the right shoulder. The aberrant course of this vessel
should be confirmed by a coronal view (Figure 5B).
Clinical Meaning
This condition is usually an incidental and isolated asymp-
tomatic anomaly, which has been found in 0.5% of large
autopsy series and in 0.6% of radiologic findings.
26,27
According to the literature, the prevalence of an aberrant
right subclavian artery varies substantially (0.4%–1.9%),
being an isolated finding in 46% of cases.
1
Congenital car-
diac defects seem to be highly associated (≈20%) with this
condition in both euploid and aneuploid fetuses,
although these anomalies seem to be more common in the
latter.
28–31
The most frequent congenital heart diseases
are atrioventricular septal defects and a persistent left
superior vena cava.
28–31
Chromosomal abnormalities, mainly Down syndrome,
are also related to an aberrant right subclavian artery in
approximately 23.2% of cases, with variations depending
on its association with other structural malformations.
1
In fact, when isolated, an aberrant right subclavian artery
has not shown any association with Down syndrome,
according to a recent meta-analysis.
1
An aberrant right sub-
clavian artery has also been associated with other genetic
disorders, especially 22q11 microdeletion, which is found
in conotruncal cardiac anomalies.
9,10
Rare Variants
Cases of complete vascular ring formation have been
described when there is a right-sided ductus arteriosus
between the aberrant right subclavian artery and the right
pulmonary artery.
32
After birth, with the closure of the
right-sided ductus arteriosus, the distal part of the right aor-
tic arch persists as the diverticulum of Kommerell. It is the-
oretically possible for a left aortic arch to be associated with
an aberrant origin of the right brachiocephalic artery, but
thus far, this association has not been reported.
20
Bravo et al—Sonographic Views of Fetal Aortic Arch Anomalies
J Ultrasound Med 2016; 35:237–251240
Figure 2. Normal embryonic development of the aortic arch. A, Hypothetical model of the embryonic double aortic arch and double ductus arte-
riosus. B, Fetal stage of the normal aortic arch. Physiologic distal regression of the right aortic arch and right ductus arteriosus has occurred, lead-
ing to a single left aortic arch and left ductus arteriosus. Supra-aortic vessels from the right aortic arch have turned into the brachiocephalic artery.
BA indicates brachiocephalic artery; DA, ductus arteriosus; LAo, left aortic arch; LCCA, left common carotid artery; LDA, left ductus arteriosus; LPA,
left pulmonary artery; LSA, left subclavian artery; PA, pulmonary artery; RAo, right aortic arch; RCCA, right common carotid artery; RDA; right ductus
arteriosus; RPA, right pulmonary artery; RSA, right subclavian artery; and T, trachea.
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Right Aortic Arch With an Aberrant Left Subclavian
Artery
Embryologic Origin
A right aortic arch with an aberrant left subclavian artery
results from abnormal persistence of the embryonic right
aortic arch and abnormal regression of the left arch between
the origins of the left common carotid artery and the left
subclavian artery, the latter originating from the distal part
of the left aortic arch (Figure 3). The aberrant artery may
run either between the trachea and the esophagus (most
collateral arteries) or behind the esophagus.
33
The ductus
arteriosus is usually left sided, connecting the left pul-
monary artery to the distal remnant of the left aortic arch
(Figure 6). This combination is the second most common
type of ring reported.
J Ultrasound Med 2016; 35:237–251 241
Bravo et al—Sonographic Views of Fetal Aortic Arch Anomalies
Figure 3. Schemes of the anatomic transverse view at the level of the 3-vessel and trachea view. The center image represents the embryonic stage
of 2 aortic arches and 2 ducti arteriosi. From this stage and depending on the point and extent of regression (gray area), we may find the following:
A, normal left aortic arch; the regression occurs in the distal part of the right aortic arch and right ductus arteriosus; B, left aortic arch with an aber-
rant right subclavian artery; C, right aortic arch with mirror branching; D, double aortic arch; and E, right aortic arch with an aberrant left subclavian
artery. ALSA indicates aberrant left subclavian artery; and ARSA, aberrant right subclavian artery; other abbreviations are as in Figure 2.
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Sonographic Findings
In this case, the 3-vessel and trachea view shows displace-
ment of the aortic arch to the right of the trachea, forming
a U shape instead of a V shape. The left-sided ductus arte-
riosus usually persists and, with the right aortic arch, encir-
cles the trachea and esophagus from behind, resulting in a
vascular ring. The transverse section of the superior vena
cava remains in its position (Figure 6A). As in the previ-
ous section, an aberrant vessel, the aberrant left subclavian
artery, can be seen at the level of the aortic isthmus, but this
time, its course is posterior to the trachea toward the left
upper limb. A coronal view also allows the visualization of
this anomaly (Figure 6B).
Clinical Meaning
The prevalence of a fetal right aortic arch with an aberrant left
subclavian artery has been estimated as 1 to 1.7 per 1000
pregnancies.
3,7,34,35
This aortic arch pattern shows a low asso-
ciation with congenital heart diseases (6.6%–33.3%), with
most being ventricular septal defects, tetralogy of Fallot and
pulmonary atresia with a ventricular septal defect.
6,7,35,36
However, its association with chromosomal abnormalities,
especially 22q11 microdeletion, seems to be higher, occur-
ring in 4.3% to 32% of cases, according to the literature,
despite the absence of congenital heart disease.
6-9,37
The clinical implications of the vascular ring will be
observed after birth with the closure of the ductus arteriosus.
The left limb of the U-shaped loop disappears, whereas the
distal remnant of the left aortic arch persists as the diver-
ticulum of Kommerell. This expansion during fetal life
receives blood flow that comes from the left-sided ductus
arteriosus. At birth, as the ductus arteriosus closes, the
blood flow comes from the descending aorta.
20
This vascular ring is usually not as tight as that made
by a double aortic arch; thus, according to prenatal series, up
to 96% of cases are asymptomatic after birth.
8
The severity
of the esophageal and tracheal compression varies accord-
ing to the size of the diverticulum.
Bravo et al—Sonographic Views of Fetal Aortic Arch Anomalies
J Ultrasound Med 2016; 35:237–251242
Figure 4. Fetal transverse views included in the cardiovascular system sonographic evaluation protocol. A, Three-vessel and trachea view with nor-
mal anatomy. B, Subclavian artery view: handlebar positioning of the subclavian arteries in a healthy fetus. Ao indicates aorta; IV, innominate vein; L,
left; R, right; and SVC, superior vena cava; other abbreviations are as in Figure 2.
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Rare Variants
A possible variation is the rarely occurring right aortic arch
with a right-sided ductus arteriosus and an aberrant left
subclavian artery. It is secondary to the abnormal regres-
sion of the left-sided ductus arteriosus and aortic arch
between the left common carotid artery and the left sub-
clavian artery and the persistence of their symmetric arches
on the right side. The sonogram would also show a V-
shaped vascular structure on the right of the trachea instead
of on the left. This V image should not confound observers
and make them think of normal anatomy, since the fetal
position and the laterality of other organs should also be
assessed to ensure the diagnosis. The aberrant left subcla-
vian artery can be seen behind the trachea to the left fetal
shoulder, forming a vascular sling.
20
This variant seems to
be more associated with cardiac anomalies.
38
A right aortic arch with an aberrant origin of the left
brachiocephalic artery is rare.
39
It results from abnormal
regression of the left aortic arch proximal to the origin of
the left common carotid artery. The persisting ductus arte-
riosus is usually left sided, completing a vascular ring.
Right Aortic Arch With Mirror Image Branching
Embryologic Origin
A right aortic arch with mirror image branching is caused
by abnormal regression of the left aortic arch distal to the
origin of the left subclavian artery (Figure 3). In this pattern,
the persisting ductus arteriosus is usually on the left, con-
necting the base of the left brachiocephalic artery or the
descending aorta to the left pulmonary artery.
38
Sonographic Findings
In a 3-vessel and trachea view, a right aortic arch with mir-
ror image branching depends greatly on the laterality of the
ductus arteriosus. Predominant persistence of a left
8,9,20,38
or
right ductus arteriosus
3,6
varies according to the literature
consulted. As reported by most authors, a left-sided ductus
arteriosus is the one that usually persists, either from the left
pulmonary artery to the proximal descending aorta (form-
ing a vascular ring) or from the left pulmonary artery to the
left brachiocephalic artery (no vascular ring). When a right-
sided ductus arteriosus persists, there is no vascular ring.
Depending on the laterality of the ductus arteriosus, we
J Ultrasound Med 2016; 35:237–251 243
Bravo et al—Sonographic Views of Fetal Aortic Arch Anomalies
Figure 5. Fetal transverse views in a case of a left aortic arch with an aberrant right subclavian artery. A, Three-vessel and trachea view. The aortic
arch appears on the right of the trachea, forming a U shape. B, Subclavian artery view. The normal handlebar positioning of the subclavian arteries
is absent, and the arteries appear straight. Abbreviations are as in Figures 2–4.
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obtain different sonographic findings in the 3-vessel and
trachea view. When the ductus arteriosus is connected to
the left brachiocephalic artery, it is not visible. However,
when it is connected to the descending aorta, a typical U
shape instead of a V shape can be observed encircling
the trachea, where the right prong of the U is formed by
the right aortic arch (Figure 7A). In cases of a persistent
right-sided ductus arteriosus a V shape formed by the right
aortic arch and the right ductus arteriosus is observed to
the right of the trachea.
In the subclavian view, both subclavian arteries maintain
their normal positions in an antetracheal location despite
the fact that the supra-aortic branching shows a mirror
image. The first branch from the right aortic arch is the left
brachiocephalic artery, followed by the right common
carotid artery and the right subclavian artery (Figure 7B).
In some cases of a right aortic arch, the diagnosis can
be suspected in a 4-chamber view when the descending
aorta is closer to the right of the spine than it should be.
However, this appearance is not a reliable sign, since the
descending aorta in a right aortic arch commonly crosses
to the left in the mid thorax.
37
Clinical Meaning
The prevalence of a right aortic arch with mirror image
branching is approximately 3.5 per 1000 in high-risk pop-
ulations,
7
with 13.6% to 47% of cases having aortic arch
anomalies
3,9
and 42% to 62% having a right aortic arch.
6
The incidence of congenital heart disease associated with
this type of aortic arch ranges from 91.5% to 100%.
3,6,7,35
In one series, the odds ratio of a fetus having congenital
heart disease in which a right aortic arch with mirror image
branching was detected was 297.4 (95% confidence inter-
val, 40.4–2186.8).
7
The most common associated con-
genital heart disease is tetralogy of Fallot (41%–57%).
7
Other frequent associations are pulmonary atresia
with a ventricular septal defect (10.3%–36%), a common
arterial trunk (13%–36%), and a double-outlet right ventri-
cle (10.3%).
6,7,40,41
Extracardiac anomalies are also common
(≈20%–22%).
6,7
The presence of extracardiac anomalies
(other than situs anomalies in heterotaxy syndromes)
have been significantly associated (60%) with 22q11
microdeletion.
6
In this type of right aortic arch, the inci-
dence of 22q11 microdeletion described ranged from
13.3% to 25%, especially in cases affected by conotruncal
Bravo et al—Sonographic Views of Fetal Aortic Arch Anomalies
J Ultrasound Med 2016; 35:237–251244
Figure 6. Fetal transverse views in a case of a right aortic arch with an aberrant left subclavian artery. A, Three-vessel and trachea view. The aortic
arch is located on the right of the trachea, forming a U shape. B, Subclavian artery view. The normal handle-bar positioning of the subclavian arter-
ies is absent. Abbreviations are as in Figures 2 and 4.
3502jum221-278 copy_Layout 1 1/20/16 12:42 PM Page 244
congenital heart disease or extracardiac malformations.
6,8,9
An association of a right aortic arch with mirror image
branching with heterotaxy syndromes is also common.
6
The outcome of these cases depends mainly on the
associated cardiac and extracardiac malformations as well
as the presence of chromosomal abnormalities. In most
cases, the absence of a vascular ring or sling minimizes the
presence of compressive symptoms after birth.
2,3,6
Rare Variants
It is less common for the ductus arteriosus to be either on
the right or bilateral.
Circumflex Retroesophageal Aortic Arch
Embryologic Origin
This condition is a rare anomaly in which the aortic arch
and the proximal descending aorta are located on oppo-
site sides of the spine. It occurs more frequently with a
right-sided aortic arch, and the branching pattern of the
supra-aortic arteries is variable. When it occurs with a right
aortic arch, the arch gives rise to the left common carotid,
right common carotid, and right subclavian arteries from its
segment on the right side of the trachea. Then the arch
makes a sharp oblique leftward and downward turn to
connect with the left-sided descending aorta. The left
subclavian artery arises from the transitional point of the
retroesophageal portion of the arch. It may be considered
an aberrant artery, since it is the last, instead of the first,
branch of the right aortic arch. In most cases, the left sub-
clavian artery arises from the aorta through the diverticu-
lum of Kommerell. The left-sided ductus arteriosus
connects the diverticulum to the left pulmonary artery,
forming a vascular ring.
20
Hypoplasia of the retroe-
sophageal segment of the aortic arch is common.
42
Sonographic Findings
The 3-vessel and trachea view shows a D-shaped structure
around the trachea, which is formed by the right aortic arch
with its retrotracheal segment and the left-sided ductus arte-
riosus on the opposite side completing the vascular ring.
43
J Ultrasound Med 2016; 35:237–251 245
Bravo et al—Sonographic Views of Fetal Aortic Arch Anomalies
Figure 7. Fetal transverse views in a case of a right aortic arch with mirror image branching. A, Three-vessel and trachea view. The aortic arch is
located on the right of the trachea, forming a U shape. B, Subclavian artery view: antetracheal course of the subclavian arteries. Abbreviations are as
in Figures 2 and 4.
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The aberrant left subclavian artery is visible, and its origin
is located in the retrotracheal area of the aortic arch. In the
subclavian artery view, the left subclavian artery is not in
its correct antetracheal position, which suggests an aber-
ration. As in previous cases, a coronal view would allow
visualization of the left subclavian artery from its origin.
Clinical Meaning
This anomaly has been scarcely seen in the prenatal setting,
mainly because of its rarity and its differential diagnosis
with a simple right aortic arch with an aberrant left sub-
clavian artery.
43,44
The association with congenital heart
disease is common, and it can be responsible for compres-
sive symptoms.
45
Anomalies With 4 Vessels in the 3-Vessel
and Trachea View
Double Aortic Arch
A double aortic arch is the tightest and most commonly
identifiable form of vascular ring.
18
Embryologic Origin
A double aortic arch is formed by the persistence of both
the right and the left embryonic aortic arches, one on each
side of the trachea and esophagus, without regression of
any segment (Figure 3). An arterial duct, more frequently
the left one, persists, although some cases with bilateral ducts
have been described.
2,43
Each aortic arch gives rise to com-
mon carotid and subclavian arteries. Usually, the right arch
is larger than the left arch. In general, the apex of the larger
arch is higher than that of the smaller arch. Occasionally, a
segment of one arch (usually the left one) may be atretic
and almost always distal to the subclavian artery. The prox-
imal descending aorta is left sided in just more than two-
thirds of patients a with double aortic arch, is right sided in
almost all of the rest, and rarely occupies a neutral midline
position.
20
Sonographic Findings
During fetal life, when the ductus arteriosus is patent, the
arrangement of the 2 arches and a patent arterial duct (usu-
ally the left) produces an image of a trident or a number 9
or number 6 configuration in a 3-vessel and trachea view
on fetal echocardiography. In a fetal cephalic presentation,
a number 6 configuration can be observed when the fetal
dorsum lies on the right, but when it lies on the left, a num-
ber 9 configuration is shown (Figure 8A). It is, in any case,
an image of 4 vessels instead of 3, with these vessels being
the right and left aortic arches, the ductus arteriosus (left or
right sided), and the superior vena cava. Since one of the
arches, typically the left one, is smaller, the sonographic
sizes of the arches are expected to be different. Even when
an atretic segment is present, it may be difficult to visualize,
since an image of arch interruption appears, which is some-
thing that makes a differential diagnosis with a right aortic
arch a challenge. Thus, proper identification of the branch-
ing pattern is essential.
2,7,37
In the subclavian artery view, both the left and the
right subclavian arteries must follow an antetracheal
course, as in normal circumstances (Figure 8B). The pres-
ence of an aberrant artery in this view or in the 3-vessel and
trachea view rules out a double aortic arch, since no other
pattern of supra-aortic branching has been described for a
double aortic arch. A coronal posterior view shows both
aortic arches giving rise to the common carotid and sub-
clavian arteries from their respective sides.
43
Clinical Meaning
The prevalence of a prenatal double aortic arch is unknown,
since it is a less common aortic arch anomaly and it is usually
added to series of right aortic arch cases.
3,7,35,46
A double aor-
tic arch is the aortic arch anomaly most frequently associ-
ated with the development of airway and esophageal
compression after birth.
8,20
Among their series of aortic
arch anomalies, most authors have reported that a double
aortic arch was responsible for a higher number of cases
with compressive symptoms in early childhood and the
need for surgery compared to other anomalies causing
rings, such as a right aortic arch with an aberrant left sub-
clavian artery
3,5
: the reason being the tightness of the vas-
cular ring formed by both aortic arches passing over the
respective bronchi to join at the thoracic descending aorta.
Based on the literature, 74% of double aortic arch cases
manifest symptoms in the early years and require surgery
to relieve them.
47
Seventy-five percent of the symptoms
(stridor, cough, asthma, respiratory distress, apnea, recur-
rent episodes of pneumonia, and dysphagia) appear early
during infancy, ranging from mild-to-severe respiratory
obstruction and apnea.
36
Cardiac and extracardiac anomalies are less common
in a double aortic arch than in other aortic arch anomalies.
Approximately 17.1% of double aortic arch cases are asso-
ciated with congenital heart disease: mainly ventricular
septal defects and double outlet right ventricles.
47
There seems to be a low association with 22q11
microdeletion in the absence of congenital heart disease,
given that most cases affected by this chromosomal abnor-
mality have congenital heart disease or extracadiac defects.
Among patients with a double aortic arch, those with an
Bravo et al—Sonographic Views of Fetal Aortic Arch Anomalies
J Ultrasound Med 2016; 35:237–251246
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atretic minor arch had a significantly higher rate of dele-
tion than those with a patent minor arch, but there was no
difference between patients with left and right dominance
of the double arch.
9
Discussion
The objective of this article is to explore fetal aortic arch
anomalies in detail, highlighting the relevance of assessing
the supra-aortic branching vessels during prenatal sono-
graphic evaluations to help in their differential diagnosis
and determine their prognosis.
The utility of the 3-vessel and trachea view for assess-
ment of conotruncal malformations and aortic arch anom-
alies has been proven, as shown by the growing number of
publications reporting its use in the last decade.
8,34,35,46
However, systematic assessment of the supra-aortic vessels,
mainly the subclavian arteries, is not a common practice in
many units. In this sense, this review tries to focus on the
possible improvements this view could offer for diagnostic
purposes.
In the last decades, the use of 5 axial sonographic views
has been the standardized method for assessment of the fetal
heart and great vessels.
48
This method consists of the pro-
gressive addition of axial views to the basic 4-chamber view to
improve the detection rate of congenital heart disease.
11–14
These axial views have been added to increase the detection
rate of cardiac anomalies, progressively changing the way
the fetal heart is explored. Hence, the addition of the sub-
clavian artery view to the standard fetal heart exploration
means the acquisition of a slightly cranial view beyond the
recommended 5 views with a simple swiping movement.
This area of the fetal thorax is not included in the systematic
exploration of the heart but can be particularly useful when
a congenital heart disease or an aortic arch anomaly is sus-
pected and even in cases of apparent normal anatomy.
The addition of the axial views included in the car-
diovascular system sonographic evaluation protocol to the
recommended 5 axial views for assessment of a more
extended fetal cardiovascular system may provide certain
advantages. In particular, the addition of the subclavian
artery axial view could be a valuable tool for confirming
J Ultrasound Med 2016; 35:237–251 247
Bravo et al—Sonographic Views of Fetal Aortic Arch Anomalies
Figure 8. Fetal transverse views in a case of a double aortic arch. A, Three-vessel and trachea view. This view shows 4 vessels instead of 3, confirming
a number 6 configuration. There is an aortic arch on each side of the trachea. B, Subclavian artery view. Each subclavian artery arises from the ipsi-
lateral aortic arch. Abbreviations are as in Figures 2 and 4.
3502jum221-278 copy_Layout 1 1/20/16 12:42 PM Page 247
normal or abnormal anatomy
1,24
and to improve the dif-
ferential diagnosis of aortic arch anomalies: eg, the differ-
ent types of right aortic arches (with a left subclavian artery
versus mirror imaging branching) and differentiation
between a double aortic arch and a right aortic arch with a
persistent left-sided ductus arteriosus.
6,7,35
Assuming that
these entities show different ranges of associated conditions
(congenital heart disease and 22q11 microdeletion), this
view allows physicians to offer additional testing and a
more precise prognosis to parents.
The usefulness of the subclavian artery view combined
with the 3-vessel and trachea view for detection of an
aberrant right or left subclavian artery is substantiated in
the clinical implications of these anomalies. Regardless
of the laterality of the aortic arch, these anomalies are asso-
ciated with a higher incidence of 22q11 deletion
10
even
without congenital heart disease.
8,9
Both entities have been
reported to be associated with congenital heart dis-
ease,
6,7,35,36
and specifically, an aberrant right subclavian
artery has also been studied as an independent marker for
Down syndrome, with a wide range of positive likelihood
ratios from 0 to 3.941.
49
Prenatal detection of an aortic arch anomaly, even
when it is isolated, provides several benefits. First, these
defects have been related to a wide spectrum of congenital
heart disease; thus, there is a consensus that any fetus
affected by an aortic arch anomaly should undergo detailed
echocardiography performed by specialists in this field,
given the high probability of a concurrent congenital
heart disease.
1,3,8,43,50
Second, the prenatal awareness of
an aortic arch anomaly secondary to vascular rings may
help pediatricians in the early diagnosis and management
of symptomatic neonates and children.
34,35
Finally, aortic
arch anomalies have been frequently associated with chro-
mosomal abnormalities, including 22q11 deletion.
9
Based
on this potential association, fetal karyotyping should be
considered, although it is a controversial test because of
certain conditions with a low risk of aneuploidy. For most
investigators, the detection of an aortic arch anomaly
together with a congenital heart disease is an indication for
invasive testing. However, it is not so clear whether isolated
cases should be karyotyped or have fluorescence in situ
hybridization to detect 22q11 deletion.
1,3,8,43,50
In cases of
an isolated left aortic arch with an aberrant right subclavian
artery, the most recent meta-analyses suggest a lack of asso-
ciation with Down syndrome
1,24
; however, controversy is
still ongoing, given that isolated cases with prenatal or post-
natal identification of trisomy 21 have been described in
8% of cases in the literature.
50,51
In cases of an isolated right
aortic arch with an aberrant left subclavian artery, more
studies are required to firmly discard karyotyping, since
cases with 22q11 deletion without congenital heart disease
have been reported.
9
In these situations, special attention should be paid to
minor markers or risk factors, which may help the physician
provide the parents with the proper genetic counseling and
help them opt for a conservative approach, invasive testing,
or even noninvasive testing (cell-free fetal DNA analysis).
In this context, sonographic assessment of the fetal thymus
can be useful for predicting 22q11 deletion when the thy-
mus is hypoplastic or absent in association with a cardiac
anomaly.
3,51,52
However, there are hardly any studies on
thymus assessment and the prevalence of 22q11 deletion
in cases of an isolated aortic arch anomaly without congen-
ital heart disease. Although some authors suggest that it
could be useful for predicting the deletion,
53
further studies
are needed.
Certain aspects about the prognosis of aortic arch
anomalies should be taken into consideration. First, when
the anomaly is accompanied by a congenital heart dis-
ease or a chromosomal abnormality, the nature and
severity of these associated anomalies are the factors that
may modify the prognosis.
1,7,46
The aortic arch anomaly
by itself may be asymptomatic in many cases, with the
exception of anomalies forming tight vascular rings.
Second, the development of tracheoesophageal symp-
toms of compression usually occurs early in life, especially
in cases of a double aortic arch once the ductus arteriosus
regresses and the ligamentum arteriosus appears.
47
However, the occurrence of compressive phenomena
could happen as early as in fetal life in the form of a con-
genital high airway compression syndrome
46,54
or as late
as in adulthood. In adults, aortic arch anomalies with an
aberrant subclavian artery and the diverticulum of
Kommerell (left aortic arch with an aberrant right sub-
clavian artery and right aortic arch with an aberrant left
subclavian artery) are the most likely to cause symp-
toms.
20,36
Symptomatic cases, whenever they occur, are
subject to vascular surgery to relieve the pressure.
Postnatal Studies
Most authors convey that postnatal radiologic examina-
tions with computed tomography or magnetic resonance
imaging are not necessary in all cases of aortic arch anomalies
and should be saved for symptomatic cases or those in which
anatomic details remain uncertain after postnatal echocar-
diography performed by experienced cardiologists.
3,7,35
Fetal sonography provides a more appropriate acoustic
window compared to postnatal evaluation, since an air bron-
chogram produces shadowing that reduces its reliability.
2
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For this reason, an accurate diagnosis in fetal life could help
design an adequate follow-up strategy and avoid any
unnecessary delay in diagnosis during postnatal life.
The controversy about postnatal symptoms of aortic
arch anomalies is still unresolved when comparing prenatal
and postnatal series. According to prenatal studies, most
of these vascular abnormalities are asymptomatic after
birth, with the exception of a double aortic arch and some
cases of a right aortic arch with an aberrant left subclavian
artery.
8,34
However, pediatricians report that 65% of aortic
arch anomalies are symptomatic, most being double
aortic arch cases requiring surgery to release the compres-
sion.
55,56
Moreover, between 43% and 61% of cases with a
right aortic arch and an aberrant left subclavian artery and
between 29% to 64% of cases with a left aortic arch and an
aberrant right subclavian artery will eventually require vas-
cular surgery secondary to the onset of compressive symp-
toms.
52,53
This lack of consensus negatively affects the
accuracy of the prognosis given to parents. A combined
effort between obstetricians and pediatricians specializing
in this field is of most importance.
Conclusions
Aortic arch anomalies are uncommon in prenatal life, but
when present, they can be either isolated or, more fre-
quently, associated with other anomalies, including chro-
mosomal defects such as 22q11 deletion. Detection of fetal
aortic arch anomalies should be performed by using the
3-vessel and trachea view, which can be improved by
the addition of the subclavian artery view, according to the
cardiovascular system sonographic evaluation protocol,
17
which is essential for establishing the arch branching pat-
tern and can contribute to the differential diagnosis and
prognosis of these entities.
After the diagnosis of these anomalies, detailed
echocardiography and fetal scanning is recommended to
rule out associated malformations. Karyotyping including
detection of 22q11 microdeletion should be offered to
parents mainly when other related conditions are found.
The prognosis of aortic arch anomalies will depend on the
associated anomalies and the risk of tracheoesophageal
compression.
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