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 
have colds.
     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.

Lateral 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 

View esophagram.

     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 
subclavian artery.

     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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Web Page Author:
Loren Yamamoto, MD, MPH
Professor of Pediatrics
University of Hawaii John A. Burns School of Medicine