Difficulty Breathing Throughout Infancy
Radiology Cases in Pediatric Emergency Medicine
Volume 6, Case 19
Loren G. Yamamoto, MD, MPH
Kapiolani Medical Center For Women And Children
University of Hawaii John A. Burns School of Medicine
This is a 6-month old male who presents to the
pediatric clinic with difficulty breathing. He has had
similar episodes in the past. He has been diagnosed
with asthma and has been treated with albuterol with
only modest improvement. He has some nasal
congestion, but no fever, vomiting or diarrhea. He
feeds well and he has been gaining weight well.
His past history is remarkable for multiple upper
respiratory infections and wheezing during the past
several months. He was born at term. His family
history is significant for asthma in several relatives and
his older siblings. He has three siblings who currently
Exam: VS T 37, P 114, R 39, BP 100/75, oxygen
saturation 99% in room air. He is alert, active, and in
no distress. He is not toxic. HEENT significant for
clear nasal mucus, normal TM's and a clear pharynx
with normal oral mucosa. Heart regular without
murmurs, but his breath sounds are noisy so it is
difficult to be sure. He has mild inspiratory and
expiratory "wheezing". His lung fields demonstrate
good aeration. He has no retractions. His abdomen is
soft, non-tender and without organomegaly. His
neurologic exam is unremarkable.
An albuterol aerosol is administered and following
this, his lung exam is unchanged. A chest radiograph is
ordered. An airway anomaly is also suspected so a
lateral neck is also ordered.
View CXR PA view.
View lateral neck.
This is a 6-month old child with a history of several
episodes of dyspnea, noisy breathing and/or wheezing.
A chest or airway anomaly of some sort is suspected.
Take a minute to review these carefully.
The PA view of the chest is unremarkable although
a right sided aorta can be suspected here. The lateral
view of the chest demonstrates a very narrow tracheal
air column which is also bent suggesting extrinsic
compression of the trachea. The lateral neck is
This esophagram demonstrates extrinsic compression
of the esophagus consistent with a vascular ring.
A vascular ring is a malformation of the aortic arch
that results in vascular branches or major blood vessels
encircling the trachea and esophagus. In nearly all
instances, a right-sided aortic arch is present. In a
double aortic arch (one of the most common vascular
ring malformation patterns), the two arches encircle the
trachea and esophagus.
See figure 1 - Double aortic arch.
In other vascular ring malformations, vascular
remnants such as the ligamentum arteriosum (formerly
the ductus arteriosus) may be part of the ring encircling
the trachea and esophagus. In our patient's case here,
further studies delineate a right sided aortic arch with an
anomalous left subclavian artery, in which the ring is
completed with a left sided ductus arteriosus which
closes to become the ligamentum arteriosum.
See figure 2 - Right sided aorta with anomalous left
Compare figures 1 and 2 to the normal anatomy of
the aorta in its relationship to the trachea and
See normal aorta.
Note that the normal aortic arch crosses over the left
mainstem bronchus. This is the normal left sided aortic
arch. In the vascular ring malformations diagrammed in
figures 1 and 2, note that the aortic arch passes over
the right mainstem bronchus instead. This is an
abnormal right sided aortic arch. In figure 1 (the double
aortic arch), the aortic arch bifurcates such that one half
of the aorta crosses over the left mainstem bronchus,
while the other half of the aorta crosses over the right
mainstem bronchus. In figure 2 (the right sided aorta
with anomalous left subclavian), the aortic arch crosses
only over the right mainstem bronchus.
Review figures 1 and 2 again.
Recognition of the right sided aortic arch is often a
valuable clinical clue in suspecting a vascular ring.
A vascular sling (as opposed to a vascular ring) is
said to be present when the vessels form an incomplete
circle around the trachea and esophagus.
Children with vascular rings are often diagnosed
during infancy, but presentations later in life my occur in
more mild cases and many cases are totally
asymptomatic. Presenting symptoms are usually due
to tracheal or esophageal compression such as stridor,
noisy breathing, frequent respiratory infections,
wheezing, dysphagia, choking, apnea, wheezing,
croupy cough, hoarse cry, etc. A typical presenting
history is that of noisy breathing since birth. It is
common for these infants to have more severe
symptoms during a respiratory infection. A young infant
with a history of "asthma" is another typical way that
these patients present. Sometimes these children are
diagnosed with cardiac disease, but the vascular ring
may be occult until an appropriate imaging study is
The key in making the diagnosis is to suspect an
airway problem based on symptoms described by the
parents. Clinical findings may or may not be present
during an examination. Two view chest radiographs are
useful in identifying many pulmonary and cardiac
anomalies, but the findings are often subtle. Since a
right sided aortic arch is almost always present in a
vascular ring, identifying this on a chest radiograph is
critical. A right sided aortic arch is defined as an aortic
arch that crosses over the right mainstem bronchus
instead of the usual left mainstem bronchus. Thus, the
arch itself may not necessarily occupy the right
hemithorax. The normal left sided aortic arch normally
pushes the carina to the right as it courses over the left
mainstem bronchus. This slight deviation in the normal
tracheal air shadow can often be appreciated on the AP
or PA view of the chest radiograph. In a right sided
aortic arch, the carina deviates to the left instead as the
aorta courses over the right mainstem bronchus.
See figure 3.
The diagram on the left illustrates the rightward
deviation of the distal trachea which occurs when the
normal left sided aorta crosses over the left mainstem
bronchus. The diagram on the right illustrates the left
sided deviation of the distal trachea which occurs when
the right sided aorta crosses over the right mainstem
In a double aortic arch, leftward deviation of the
carina may not be visible on the chest radiograph
because both left and right aortic arches are present.
However, since a double aortic arch often forms a large
caliber ring, tracheal compression is often visible on the
lateral view of the chest radiograph. In cases where no
carina deviation is present and the side of the aorta
cannot be determined, a double aortic arch should be
The lateral view of the chest radiograph may reveal
a narrowed or constricted tracheal air column (as was
seen in the patient in this case). Once an airway
anomaly or right sided aortic arch is suspected on plain
chest radiographs, a more advanced imaging study
should be performed to delineate the anatomy
Occasionally, bronchial compression is severe and
unilateral hyperinflation can be seen on the AP or PA
view of the chest radiograph. This usually suggests a
pulmonary artery sling, a bronchial anomaly or
compression of the bronchus by some other structure.
An esophagram (barium swallow) is helpful in
making the diagnosis and historically, the esophagram
was heavily relied upon to delineate the malformation
until angiography was performed. Currently, advanced
imaging methods such as echocardiography, CT
scanning, magnetic resonance imaging (MRI) and
magnetic resonance angiography (MRA) may eliminate
the need for esophagrams, since they are non-invasive
and they define the anatomy of the malformation well.
Treatment focuses on the surgical correction of the
malformation with the goal of relieving the patient's
Morrow WR, Huhta JC. Aortic Arch and Pulmonary
Artery Anomalies (Chapter 59). In: Garson J, Bricker
JT, Fisher DJ, Neish SR (eds). The Science and
Practice of Pediatric Cardioliogy. Baltimore, Williams &
Wilkins, 1998, pp. 1347-1381.
Backer CL, Mavroudis C. Vascular Rings and
Pulmonary Artery Sling (Chapter 12). In: Mavroudis C,
Backer CL (eds). Pediatric Cardiac Surgery. St. Louis,
Mosby, 1994, pp. 147-165.
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