DOI:10.2214/AJR.04.1493
AJR 2005; 185:1248-1251
© American Roentgen Ray Society
Angiography and Dynamic Airway Evaluation with MDCT in the Diagnosis of Double Aortic Arch Associated with Tracheomalacia
M. S. M. Chan1,
W. C. W. Chu1,
K. L. Cheung2,
A. A. Arifi3 and
W. W. M. Lam1
1 Department of Diagnostic Radiology and Organ Imaging, Faculty of Medicine, The
Chinese University of Hong Kong, Prince of Wales Hospital, Ngan Shing St.,
Shatin, New Territories, Hong Kong.
2 Department of Pediatrics, The Chinese University of Hong Kong, Prince of Wales
Hospital, Shatin, New Territories, Hong Kong.
3 Department of Surgery, The Chinese University of Hong Kong, Prince of Wales
Hospital, Shatin, New Territories, Hong Kong.
Received September 22, 2004;
revised November 3, 2004;
Address correspondence to W. C. W. Chu.
Introduction
Double aortic arch is a well-known congenital vascular anomaly causing
extrinsic tracheal compression in neonates that can present with
life-threatening episodes of stridor, cyanosis, or apnea. Surgical correction
of the underlying vascular ring is the key for successful treatment for such
patients [1]. However, previous
studies have shown that as many as 30% of pediatric patients might still have
persistent airway obstruction after surgical procedures
[2,
3]. These symptoms may be
related to airway wall weakening as a result of long-standing extrinsic airway
compression. Such patients may benefit from undergoing a second operation
after evaluation with both bronchoscopy and cross-sectional imaging.
Recently, MDCT with multiplanar and 3D reconstruction has become an
important tool in the evaluation of thoracic aortic anomalies in pediatric
patients, obviating conventional angiography
[4,
5]. Dynamic
inspiratory–expiratory imaging by MDCT has been shown to be a promising
method in the evaluation of patients with dynamic airway obstruction and to
correlate well with bronchoscopic results
[6]. In this case report, we
describe the pre- and postoperative MDCT angiography findings in an infant
with double aortic arch who failed extubation after undergoing corrective
surgery. A dynamic airway evaluation was performed during the same setting of
MDCT angiography by alternately applying and withholding positive-pressure
ventilation, which simulated the inspiratory–expiratory scan. The child
was found to have tracheomalacia, which explained the airway obstruction that
persisted postoperatively.
Case Report
A 2-month-old female infant presented with repeated episodes of cyanotic
attacks and noisy breathing since birth. She was born at full term with
unremarkable antenatal history. Physical examination revealed marked subcostal
retraction with diffuse rhonchi heard. After admission to the hospital, the
child relied on mechanical ventilation through an endotracheal tube with an
internal diameter of 3.5 mm. The child experienced severe respiratory distress
whenever attempts were made to pull out the endotracheal tube more than 1 cm
from the carina.
Contrast-enhanced CT angiography of the thorax was performed using a
16-MDCT scanner (LightSpeed 16, GE Healthcare) after IV injection of 10 mL of
iodixanol (270 mg I/mL Visipaque, Nycomed) at a speed of 1 mL/sec by a power
injector. Postcontrast examination was automatically started using
bolus-tracking software (SmartPrep, GE Healthcare). The CT parameters used
included 0.625-mm slice thickness and weight-based low-dose tube current (80
kV and 150 mA). The fast-scanning technique time to cover the whole thorax
enabled temporary withholding of positive-pressure ventilation for 8 sec
before desaturation occurred in the infant. The endotracheal tube was also
placed more cranial than the normal position to avoid obscuration of the
obstructed airway segment at the distal trachea.
Preoperative MDCT study showed the presence of double aortic arch with
mirror branching that formed a complete vascular ring
(Fig. 1A) around the distal
trachea just above the carina with obliteration of the tracheal lumen
(Fig. 1B). A short segment of
tracheal narrowing was present, extending 1 cm above and toward the carina,
together with obstruction of the proximal left main bronchus
(Fig. 1C). Apart from the
vascular anomaly and tracheal narrowing, there was coexistence of a focal area
of cystic adenomatoid malformation in the right upper lobe (not shown).
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Fig. 1A —Preoperative MDCT studies (A–C) of 2-month-old
female infant with double aortic arch presenting with stridor and repeated
apnea and postoperative MDCT studies (D–G) of same patient
presenting with persistent airway obstruction after corrective surgery for
double aortic arch. Enhanced superior view of 3D volume-rendered image shows
vascular ring formed by double arch aorta that encircles trachea (T).
Arrowheads = right arch, arrows = left arch.
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Fig. 1B —Preoperative MDCT studies (A–C) of 2-month-old
female infant with double aortic arch presenting with stridor and repeated
apnea and postoperative MDCT studies (D–G) of same patient
presenting with persistent airway obstruction after corrective surgery for
double aortic arch. Enhanced axial CT image shows double aortic arch causing
total obliteration of tracheal lumen (long arrow). Soft-tissue
density in center of vascular ring is constituted of partial volume effect of
pericardium and collapsed tracheal lumen. Right arch (arrowheads) is
larger than left arch (short arrows).
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Fig. 1C —Preoperative MDCT studies (A–C) of 2-month-old
female infant with double aortic arch presenting with stridor and repeated
apnea and postoperative MDCT studies (D–G) of same patient
presenting with persistent airway obstruction after corrective surgery for
double aortic arch. Coronal 3D volume-rendered image with lower opacity
(transparency) values shows obliteration of distal trachea and left main
bronchus. The former is compressed by double aortic arch, whereas the latter
is compressed by midline descending aorta. Note that tip of endotracheal tube
(arrow) is in proximal trachea, above tracheal narrowing, while
positive-pressure ventilation is withheld at time of imaging.
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The infant was operated on with the right aortic arch ligated and divided
(Figs. 1D and
1E). The right aortic arch was
also fixed to the anterior chest wall to free up space for the trachea.
However, the child continued to depend on the ventilator and failed to be
extubated. This raised the suspicion of possible congenital tracheobronchial
anomaly associated with the vascular anomaly. MDCT of the thorax was repeated.
Besides contrast-enhanced angiography, dynamic assessment of the airway was
performed. Initially, positive-pressure ventilation was maintained during the
acquisition of CT angiography. On the 3D volume-rendered display of lower
opacity values (Fig. 1F), there
was a persistent short segment of tracheal narrowing at the level of the
remaining arch proximal to the carina. The narrowest luminal axial dimension
was 2.5 mm. Imaging of the upper thorax without IV contrast material was then
repeated with the same scanning parameters while withholding the positive
ventilatory pressure. There was complete luminal obliteration of the narrowed
segment (Fig. 1G). The findings
suggested the presence of tracheomalacia, which was confirmed by bronchoscopy.
Tracheoplasty and possible stenting were planned for the patient.
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Fig. 1D —Preoperative MDCT studies (A–C) of 2-month-old
female infant with double aortic arch presenting with stridor and repeated
apnea and postoperative MDCT studies (D–G) of same patient
presenting with persistent airway obstruction after corrective surgery for
double aortic arch. Enhanced superior view of 3D volume-rendered image shows
discontinuation and splaying of vascular ring after surgery. Arrowheads =
right arch, arrows = divided left arch.
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Fig. 1E —Preoperative MDCT studies (A–C) of 2-month-old
female infant with double aortic arch presenting with stridor and repeated
apnea and postoperative MDCT studies (D–G) of same patient
presenting with persistent airway obstruction after corrective surgery for
double aortic arch. Enhanced thick-slab (10 mm) axial image acquired with
positive-pressure ventilation. Air is visualized within tracheal lumen
(arrow), although intact left arch and remaining anterior portion of
ligated right arch are immediately abutting airway at level of narrowing.
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Fig. 1F —Preoperative MDCT studies (A–C) of 2-month-old
female infant with double aortic arch presenting with stridor and repeated
apnea and postoperative MDCT studies (D–G) of same patient
presenting with persistent airway obstruction after corrective surgery for
double aortic arch. Coronal 3D volume-rendered image with lower opacity values
acquired at same setting as D with positive-pressure applied with
endotracheal tube to simulate inspiratory phase of respiration. When compared
with preoperative image (C), left main bronchus is now normal in
caliber. There is still persistent narrowing of distal trachea at level of
remaining aortic arch.
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Fig. 1G —Preoperative MDCT studies (A–C) of 2-month-old
female infant with double aortic arch presenting with stridor and repeated
apnea and postoperative MDCT studies (D–G) of same patient
presenting with persistent airway obstruction after corrective surgery for
double aortic arch. Coronal 3D volume-rendered image with lower opacity values
acquired when positive-pressure ventilation is withheld, simulating expiratory
phase of respiration. Short segment of distal trachea is completely
obliterated, which is suggestive of airway collapse. Tracheomalacia was
confirmed by subsequent bronchoscopy.
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Discussion
Airway pathology related to vascular anomaly in neonates could be due to
the extrinsic compression, related to an anomalous relationship between the
cardiovascular structures and the tracheobronchial tree, or to tracheomalacia
as a result of long-term extrinsic compression causing weakening of the airway
wall. These findings are usually coexisting and are not mutually exclusive
[3]. Evaluation of dynamic
airway obstruction in young infants is often complex and may require multiple
imaging techniques and invasive procedures. In this case, we show the
advantages of using MDCT to investigate an airway obstruction associated with
a congenital vascular ring in an infant.
First, the isometric data collection in MDCT enables postexamination data
processing such as volume rendering and 3D and multiplanar reconstruction to
be performed with a single radiation exposure. Reconstruction in the form of
CT angiography allows the detailed anatomy of the vascular anomaly to be shown
[4] in a noninvasive way
compared with conventional angiography. The multiplanar reformat capability
and display allow visualization of the complex anomalies at different angles
without subjecting the child to multiple exposures, as in fluoroscopic planar
conventional angiography, while, at the same time, the relationship and effect
of the vascular ring on the underlying airway can also be assessed with
improved spatial resolution and image quality compared with previous reports
of images obtained on a helical CT scanner
[7].
Conventionally, tracheobronchomalacia was investigated and diagnosed by
bronchoscopy. Recently, MRI, electron beam CT, and MDCT are documented to be
useful in the dynamic evaluation of tracheal patency and, hence, to help in
the diagnosis of tracheobronchomalacia
[6,
8–10].
However, it is necessary to obtain images during both the inspiratory and
expiratory phases. In our infant patient, by alternately applying and
withholding positive ventilatory pressure on the endotracheal tube, we were
able to study the dynamic change of airway in tracheobronchomalacia under
conditions that simulated the inspiratory and expiratory phases in adult
patients without jeopardizing the ventilation in an infant with ventilatory
dependency.
The use of MDCT is also advantageous in pediatric patients with an airway
compromised in other ways. The ultrahigh speed of MDCT allows an examination
covering the whole length of the bronchial tree with data collection to be
completed within seconds at physiologic setting. MDCT is also advantageous
over bronchoscopy. It is less traumatic to young infants. Nonphysiologic
factors, such as prevention of glottic closure or forced exhalation during
bronchoscopy [8], are not
introduced. The ability to show tracheomalacia in 3D by MDCT also gives a
better understanding of the overall anatomy and quantitative analysis of the
tracheal dimension as compared with the fish-eye view in traditional
bronchoscopy in which the images are spatially distorted
[8]. The clear spatial
orientation obtained with inspiratory and expiratory cycles may help
subsequent ventilatory care of and surgical decisions regarding the
patient.
In conclusion, we propose that dynamic airway evaluation—by applying
and withholding positive ventilatory pressure alternately to simulate
inspiratory and expiratory phases—can be safely implemented in the same
setting of cross-sectional MDCT for the assessment of a tracheomalacia
component associated with a vascular ring in pediatric patients. We recommend
that dynamic airway imaging be performed routinely in the preoperative
assessment of patients with vascular rings. Knowledge of this information in
the immediate preoperative setting could potentially avoid the need for a
second operation.
References
- Sebening C, Jakob H, Tochtermann U, et al. Vascular
tracheobronchial compression syndromes: experience in surgical treatment and
literature review. Thorac Cardiovasc Surg2000; 48:164
–174[CrossRef][Medline]
- Anand R, Dooley KJ, Williams WH, Vincent RN. Follow-up of surgical
correction of vascular anomalies causing tracheobronchial compression.
Pediatr Cardiol 1994;15
: 58–61[Medline]
- Fleck RJ, Pacharn P, Fricke BL, Ziegler MA, Cotton RT, Donnelly LF.
Imaging findings in pediatric patients with persistent airway symptoms after
surgery for double aortic arch. AJR 2002;178
:1275
–1279[Abstract/Free Full Text]
- Lee EY, Siegel MJ, Hildebolt CF, Gutierrez FR, Bhalla S, Fallah JH.
MDCT evaluation of thoracic aortic anomalies in pediatric patients and young
adults: comparison of axial, multiplanar, and 3D images.
AJR 2004; 182:777
–784[Abstract/Free Full Text]
- Siegel MJ. Multiplanar and three-dimensional multi-detector row CT
of thoracic vessels and airways in the pediatric population.
Radiology 2003;229
: 641–650[Abstract/Free Full Text]
- Gilkeson RC, Ciancibello LM, Hejal RB, Montenegro HD, Lange P.
Tracheobronchomalacia: dynamic airway evaluation with multidetector CT.
AJR 2001; 176:205
–210[Abstract/Free Full Text]
- Katz M, Konen E, Rozenman J, Szeinberg A, Itzchak Y. Spiral CT and
3D image reconstruction of vascular rings and associated tracheobronchial
anomalies. J Comput Assist Tomogr 1994;19
: 564–568
- Hein E, Rogalla P, Hentschel C, Taupitz M, Hamm B. Dynamic and
quantitative assessment of tracheomalacia by electron beam tomography:
correlation with clinical symptoms and bronchoscopy. J Comput
Assist Tomogr 2000; 24:247
–252[CrossRef][Medline]
- Donnelly LF, Casper KA, Chen B, Koch BL. Defining normal upper
airway motion in asymptomatic children during sleep by means of cine MR
techniques. Radiology 2002;223
: 176–180[Abstract/Free Full Text]
- Boiselle PM, Feller-Kopman D, Ashiku S, Weeks D, Ernst A.
Tracheobronchomalacia: evolving role of dynamic multislice helical CT.
Radiol Clin North Am 2003;41
: 627–636[CrossRef][Medline]
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Introduction
Case Report
