AJR 2001; 176:1606-1607
© American Roentgen Ray Society
The Aortic Sling
Malpositioned Aortic Arch Surrounding and Compressing the Trachea in a Patient with Thoracic Deformity
Lane F. Donnelly
Children's Hospital Medical Center Cincinnati, OH
45229-3039
Extrinsic compression of the trachea and central airways is one of more
common diseases of the central airways in children, and vascular rings such as
the double aortic arch, other arch anomalies, and anomalous origin of the left
pulmonary artery are among the best-known vascular causes of tracheal
compression [1]. However, there
are a number of other vascular causes of airway compression in children that
are not as well known and, yet, are not rare occurrences
[2]. Because of the confined
space of the superior mediastinum, almost any abnormally enlarged structure,
malpositioned structure, or mediastinal mass has the potential to cause airway
obstruction [2]. In many
tertiary centers, to which children with multiple medical problems are
frequently referred, these other causes of airway compression may be
encountered at rates similar to those of the classic vascular rings. The more
common of these other causes of airway compression include an enlarged
ascending aorta, malpositioned descending aorta, enlarged pulmonary arteries,
enlarged left atrium, nonvascular mediastinal masses, and abnormalities of
chest wall configuration [2,
3].
Of the well-described vascular rings, anomalous origin of the left
pulmonary artery (pulmonary sling) is the only true "sling." In
patients with this condition, the left pulmonary artery arises from the right
pulmonary artery rather than from the typical point of origin, off the main
pulmonary artery [1]. The
abnormal origin leads to the left pulmonary artery wrapping around the trachea
as it courses leftward toward the left hemithorax and passes between the
trachea and esophagus [1]. This
pulmonary sling results in compression of the distal trachea.
We recently encountered a patient in whom an "aortic sling" was
the cause of tracheal compression. A 19-year-old woman with multiple medical
problems, including severe scoliosis and a posterior thoracic mixed vascular
malformation, was examined using a contrast-enhanced CT scan of the chest
obtained because of stridor that had been refractory to medical therapy. The
scoliosis had resulted in severe thoracic deformity with a small right and
larger left hemithorax (Fig.
5A). The CT scan revealed that the patient's severe thoracic
deformity had resulted in the descending aorta being positioned much more
rightward and superior than normal (Fig.
5B). The abnormal position of the descending aorta resulted in the
aortic arch being oriented in the axial plane in a C-shaped sling
(Fig. 5B). The aortic sling
surrounded and compressed the trachea. The esophagus was in a posterior and
rightward location, not within the confines of the aortic sling.
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Fig. 5A. — Thoracic deformity leading to airway compression in
19-year-old woman with severe scoliosis. Frontal chest radiograph shows severe
scoliosis resulting in thoracic deformity. Right hemithorax is asymmetrically
small and shifted superiorly compared with left. There are spinal rods in
place.
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Fig. 5B. — Thoracic deformity leading to airway compression in
19-year-old woman with severe scoliosis. CT scan reveals severe deformity of
thorax with small right hemithorax and vertebral bodies oriented toward right,
resulting in descending aorta (D) being positioned extremely rightward
and superior. As a result, ascending aorta (A) and aortic arch are
oriented in axial plane and form sling around trachea (arrow),
leading to its compression.
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Tracheal compression as a result of abnormal thoracic configuration has
been previously reported
[2,3,4].
Abnormal thoracic configuration can be associated with a narrow
anteroposterior chest diameter that results in direct compression of the
trachea between the manubrium and spine at the level of the thoracic inlet
[3]. Also, abnormal thoracic
configuration can lead to an alteration in the anatomic relationship between
the airway and adjacent structures resulting in abnormal anterior to posterior
"stacking" of mediastinal structures and resultant tracheal
compression. This mechanism usually results in compression of the proximal
left main bronchus [3,
4]. In this patient, the
altered position of the descending aorta and orientation of the aortic arch
resulted in an aortic sling that compressed the mid trachea. I have not
previously encountered such a case. Aortic sling should be considered in the
differential diagnosis of tracheal compression occurring in patients with
thoracic deformity.
References
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Berdon WE, Baker DH. Vascular anomalies and the infant lung: rings,
slings, and other things. Semin Roentgenol
1972;7:39
-63[Medline]
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Donnelly LF, Strife JL, Bisset GS III. The spectrum of extrinsic
lower airway compression in children: MR imaging. AJR
1997;168:59
-62[Free Full Text]
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Donnelly LF, Bisset GS III. Airway compression in children with
abnormal thoracic configuration. Radiology
1998;206:323
-326[Abstract/Free Full Text]
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Donnelly LF, Frush DP. Abnormalities of the chest wall in pediatric
patients. AJR
1999;173:1595
-1601[Abstract]
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