AJR 2000; 174:355-359
© American Roentgen Ray Society
CT Angiography of Complications in Pediatric Patients Treated with Intravascular Stents
Jeff L. Fidler1,
John P. Cheatham2,
Scott E. Fletcher2,
Ameeta B. Martin2,
John D. Kugler2,
Carl H. Gumbiner2 and
David A. Danford2
1
Department of Radiology, University of Nebraska Medical Center, 981045
Nebraska Medical Center, Omaha, NE 68198-1045.
2
Joint Division of Pediatric Cardiology, University of Nebraska Medical Center
and Creighton University at Children's Hospital, 982166 Nebraska Medical
Center, Omaha, NE 68198-2166.
Received January 22, 1999;
accepted after revision July 2, 1999.
Address correspondence to J. L. Fidler.
Abstract
OBJECTIVE. Our goal was to determine whether CT angiography can
reveal complications in pediatric patients and young adults treated with
intravascular stents for obstructive vascular lesions.
CONCLUSION. CT angiography can reveal complications in pediatric
patients treated with intravascular stents for obstructive lesions.
Potentially, CT angiography could replace the more invasive conventional
angiography currently used for intravascular stent placement and follow-up
examinations.
Introduction
Obstructive intravascular lesions occur with many congenital heart
diseases. Recently, angioplasty and intravascular stents replaced surgical
treatment of vascular stenoses and obstructions
[1,2,3].
Placement of vascular stents is often difficult and, after deployment, several
complications may occur. Surveillance for these complications is usually
performed with invasive conventional angiography. The use of noninvasive CT
angiography and MR imaging is gaining popularity as an alternative method of
imaging. For pediatric patients, MR angiography is used for the evaluation of
congenital heart disease. However, MR angiography cannot be used to evaluate
intravascular stents because of the local susceptibility artifact that occurs
in the region of the stent. CT angiography avoids many of these artifacts;
however, it is not regularly used in the pediatric population because of
perceived difficulties with its performance in this age group.
In this article, we review CT angiography for the detection of vascular
complications associated with intravascular stents for obstructive vascular
lesions in pediatric patients and young adults.
Subjects and Methods Patients
During a 1-year period, we prospectively examined 14 CT angiograms for 12
patients with intravascular stents. Two patients underwent two series of CT
angiography each. Patients ranged in age from 6 to 20 years (mean age, 14
years; median age, 15 years). Two patients were older than 17 years and
technically considered adults. These patients were included because of their
underlying conditions of congenital heart disease including tetralogy of
Fallot and pulmonary stenoses. All intravascular stents were balloon
expandable stainless steel (Palmaz; Cordis Endovascular, Warren, NJ). Eight
patients had stent placement for aortic coarctation, one patient had abdominal
aortic stent placement for aortic obstruction associated with Williams
syndrome, and three patients had pulmonary artery stent placement for various
obstructive lesions.
Imaging Studies
Conventional angiography.—Posttreatment conventional
angiography was performed on all patients before CT angiography, and
conventional angiograms were available for comparison. The time between
conventional angiography and CT angiography ranged from 1 day to 2 years.
Conventional angiography was performed by an interventional pediatric
cardiologist using a biplane digital cardiac catheterization unit (TDC-4000;
Toshiba International, Tustin, CA) with cine, cut film, or digital subtraction
angiography.
CT angiography.—CT angiography was performed on patients for
whom an abnormality was detected on previous conventional angiography that
required follow-up examination. CT angiography was also performed on patients
who required follow-up imaging. CT angiography was performed on a helical
HiSpeed 9800 scanner (General Electric Medical Systems, Milwaukee, WI). One
radiologist assisted in the examination, postprocessing, and image review.
Acquisition technique.—One patient required sedation to
complete imaging. Unenhanced images were obtained (collimation, 3 mm; pitch,
1.4:1; injection rate, 3 ml/sec [using power injector for 11 patients and hand
injection for one patient]) through the region of interest to locate the stent
and calculate an optimal field of view. The largest IV catheter that could be
inserted (18- to 20-gauge) was placed in the antecubital fossa. Patency was
assessed by hand injection of saline. A 10- to 15-ml test bolus was injected
at the rate of 3 ml/sec and images were obtained every other second to
determine the optimal scan delay. Scan delay varied depending on the vessel
examined. A 5-sec delay was used for the pulmonary artery and a 10-sec delay
for the aorta. Helical images were obtained through the region of interest
with a targeted small field of view. Twelve scans were obtained during a
single breath-hold and two during quiet shallow respiration.
Postprocessing and image review.—Images were reconstructed
at 1-mm intervals and reviewed on a workstation (Advantage Windows; General
Electric Medical Systems). Multiplanar reconstructions were viewed in various
planes in relation to the stent. Three-dimensional images were produced for
selected patients using a shaded-surface display. Images were prospectively
reviewed by one radiologist for the assessment of stent placement, vessel
narrowing, stent—vessel wall separation, pseudoaneurysm or aneurysm
formation, contour abnormality, and other findings. Narrowing was defined as a
smaller caliber at stent location in comparison with the surrounding vessel.
Separation was present if the stent did not appose the vessel wall. An
aneurysm or pseudoaneurysm was present when diffuse vessel dilatation at the
stent site measured at least 150% of the normal vessel caliber in the distal
aorta [4]. Eccentricity is
suggestive of a pseudoaneurysm; however, because of the angiographic
difficulty in differentiating pseudoaneurysms from aneurysms, no distinction
was attempted. Contour abnormality was present if there was vessel
irregularity or dilatation that did not meet the criteria for an aneurysm or
pseudoaneurysm. Conventional and CT angiograms were compared for evidence of
distal migration.
Results
Except for those of one patient, CT angiograms were judged technically
adequate by a radiologist. Several factors contributed to the suboptimal
enhancement of angiograms for one patient. These factors included complex
shunt flow, decreased contrast bolus (limited because of patient age), and
breakage of IV tubing. Despite these difficulties, the angiograms still
provided diagnostic information. No complications relating to CT angiography
were encountered.
Thoracic Aorta
Eight patients with intravascular stents for aortic coarctation underwent
conventional angiography and CT angiography with concurrent findings in all
patients. For two patients, angiographic findings revealed mild persistent
narrowing at the stent site after deployment. For one patient, angiographic
findings revealed a mild contour abnormality that did not meet the criteria
for an aneurysm (Fig.
1A,1B),
whereas another patient was borderline aneurysmal. For one patient,
angiographic findings revealed a large eccentric aneurysm or pseudoaneurysm
located medially (Fig.
2A,2B).
One patient's angiograms revealed multiple findings including persistent mild
narrowing at the stent site, contour abnormality, and mild separation of the
stent from the vessel wall. Additionally, follow-up stent dilation was
performed. A second CT angiography showed improved approximation of the stent
and vessel wall (Fig.
3A,3B,3C).
For two patients with coarctation, angiographic findings revealed no
significant abnormalities after stent placement.
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Fig. 1A .—16-year-old boy with stent placement for aortic coarctation.
A and B, Conventional angiogram (A) and coronal
reformatted CT angiogram (B) reveal contour abnormality at stent site
(arrows). Note separation of stent from wall.
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Fig. 1B .—16-year-old boy with stent placement for aortic coarctation.
A and B, Conventional angiogram (A) and coronal
reformatted CT angiogram (B) reveal contour abnormality at stent site
(arrows). Note separation of stent from wall.
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Fig. 2B .—13-year-old boy with stent placement for aortic coarctation.
Three-dimensional shaded-surface display reveals similar findings to those in
A. Note external contour of aneurysm. Stent—vessel relationship
and internal features of vessel are unapparent.
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Fig. 3A .—14-year-old boy with stent placement for aortic coarctation.
A and B, Initial CT oblique sagittal (A) and axial
(B) images reveal contour abnormality (short arrow, A)
and small amount of separation along stent (long arrows).
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Fig. 3B .—14-year-old boy with stent placement for aortic coarctation.
A and B, Initial CT oblique sagittal (A) and axial
(B) images reveal contour abnormality (short arrow, A)
and small amount of separation along stent (long arrows).
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Abdominal Aorta
One patient with Williams syndrome had an aortic stent placed for long
segmental narrowing of the aorta. This aortic narrowing was associated with
proximal narrowing of the celiac axis and superior mesenteric artery as
revealed on conventional angiography. These findings were well depicted on CT
angiography (Fig.
4A,4B,4C).
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Fig. 4A .—17-year-old boy with history of Williams syndrome.
A-C, Coronal (A) and sagittal (B, C) reformatted CT
images reveal narrowing of lower thoracic and upper abdominal aorta. Note
narrowing of celiac axis (arrow, B) and superior mesenteric
artery (arrow, C).
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Fig. 4B .—17-year-old boy with history of Williams syndrome.
A-C, Coronal (A) and sagittal (B, C) reformatted CT
images reveal narrowing of lower thoracic and upper abdominal aorta. Note
narrowing of celiac axis (arrow, B) and superior mesenteric
artery (arrow, C).
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Fig. 4C .—17-year-old boy with history of Williams syndrome.
A-C, Coronal (A) and sagittal (B, C) reformatted CT
images reveal narrowing of lower thoracic and upper abdominal aorta. Note
narrowing of celiac axis (arrow, B) and superior mesenteric
artery (arrow, C).
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Pulmonary Arteries
Three patients had stent placement for obstructive pulmonary artery
lesions. One patient with stenosis of both pulmonary arteries had three stents
placed—one in the proximal right pulmonary artery, one extending from
the main pulmonary artery in the proximal left pulmonary artery bridging the
origin of the right, and one in the left pulmonary artery. Residual narrowing
and peripheral branch stenosis evident on conventional angiography were well
depicted on CT angiography (Fig.
5A,5B).
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Fig. 5A .—20-year-old woman with three pulmonary artery stents for pulmonary
artery stenoses after tetralogy of Fallot repair.
A and B, Axial CT images reveal bridging of stents of main
and right pulmonary artery (arrow, A).
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Fig. 5B .—20-year-old woman with three pulmonary artery stents for pulmonary
artery stenoses after tetralogy of Fallot repair.
A and B, In region of stents, note mild narrowing in relation
to surrounding vessel and narrowing of right pulmonary artery distal to stent
(arrow, B).
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One patient had tetralogy of Fallot with associated pulmonary artery
stenoses. Conventional angiography (after deployment of the stent) showed a
small pseudoaneurysm and probable dissection extending along the left lower
lobe pulmonary artery. CT angiography performed the day after conventional
angiography revealed a small pseudoaneurysm. A small amount of soft-tissue
density was seen tracking along the left lower lobe pulmonary artery. This
finding might have represented interval thrombosis of the dissection as seen
on conventional angiography. One patient with obstructed pulmonary artery
lesions had complex anatomy and findings. This patient had a history of
pulmonary atresia and a hypoplastic right ventricle. Multiple stents were
required for multiple stenoses. A small pseudoaneurysm developed at the site
of previous angioplasty and stent placement in the left pulmonary artery, as
shown on conventional angiography. CT angiography was less than optimal
because of the previously mentioned technical problems related to complex flow
and decreased contrast bolus; however, the pseudoaneurysm was revealed.
Nevertheless, shunt integrity was poorly visualized.
Discussion
Conventional angiography is performed to evaluate complications after
intravascular stent placement. Noninvasive CT angiography is used in follow-up
examinations of adult patients treated with intravascular stents for aortic
aneurysms, venous obstruction, and transjugular intrahepatic portosystemic
shunts
[5,6,7,8,9,10].
However, CT angiography is not regularly used in the pediatric population. Our
results show that CT angiography can be used for younger patients and can
provide information comparable with conventional angiography.
In our study, most patients were 10 years old or older and were able to
cooperate with breathing instructions. In a separate and ongoing study, we
performed CT angiography in younger patients with satisfactory results. The
modifications in our protocol when examining young patients include the
administration of sedation, scanning during quiet shallow respiration, and the
hand injection of contrast material.
Bolus tracking products are commercially available and allow image
acquisition during peak vascular enhancement
[11]. These techniques produce
reliable scan timing and reduce contrast volume. Bolus tracking (not used in
our study) makes CT angiography easier to use in young pediatric patients.
Most diagnostic information is obtained from reviewing the axial source and
reformated planes on a workstation. By varying the window and level, the
relationship of the stent to the vessel wall can be visualized. It is
imperative that the radiologist review these images on a workstation to avoid
misinterpretations. Various orientations should be examined to avoid partial
voluming artifacts, because separation or contour abnormalities may only be
seen in certain projections.
Three-dimensional images using shaded-surface—display or
maximum-intensity-projection algorithms can be obtained. Because of the
inherent method of obtaining these images, this technique is useless in
assessing the stent—wall relationship and arterial patency of the vessel
because of the high attenuation of both the stent and the contrast material.
However, three-dimensional images can provide an overview of the vessel
contour revealing contour irregularity or aneurysm formation. New
volume-rendering postprocessing software produces three-dimensional images
depicting certain structures as translucent. This technique enables the
visualization of the stent and the inner vessel
[12]. This software (not used
in our series) probably produces more informative three-dimensional images.
Further studies are necessary to evaluate this technique and to determine the
benefit of the additional diagnostic information it provides.
In our series, the vessel examined affected the quality of the reformatted
and three-dimensional images we obtained. High-quality images were obtained in
the aorta; however, vessel reformation and three-dimensional reconstruction
were problematic in the pulmonary artery. These problems related to the
multiple surrounding enhancing structures and motion artifacts.
We think that CT angiography is useful in assessing intravascular stent
placement in children with vascular obstructions. CT angiography revealed all
aneurysms or pseudoaneurysms and areas of stenosis that were identified on
conventional angiography. One dissection was poorly depicted on CT
angiography; however, this problem might be a reflection of interval
thrombosis that developed between conventional angiography and CT
angiography.
Four limitations affected our results. First, radiologists interpreted some
CT angiograms with knowledge of prior conventional angiography results.
Obviously, this observer bias affected and improved the accuracy of CT
angiography; however, this biased comparison and focused direction was
important to uncover the limitations and pitfalls of CT angiography. Second,
our report studied a small number of patients. Now that we have shown that
this technique is feasible, larger blinded prospective studies are necessary
to determine the true sensitivity and specificity of CT angiography in
comparison with conventional angiography. Third, we studied older pediatric
patients. Although the youngest patient was 6 years old, most were in their
mid to upper teens. If additional younger patients were included, more
suboptimal studies may have resulted; however, we have performed CT
angiography to screen for pseudoaneurysm on a 4-year-old patient (after
angioplasty) with aortic coarctation. Therefore, we believe this technique can
be used for younger patients. Fourth, the time between conventional
angiography and CT angiography was considerably long (>1 year) for four
patients. A radiologist might expect a change in stenosis or aneurysm during
such an interval; however, in our series, complications appeared to remain
stable.
In conclusion, CT angiography can detect complications after intravascular
stent placement. Further prospective evaluation is necessary to assess the
accuracy of CT angiography compared with conventional angiography. Technical
advances, such as bolus tracking and volume rendering, will make CT
angiography easier to use and will improve overall results.
References
-
O'Laughlin MP, Slack MC, Grifka RG, Perry SB, Lock JE, Mullins CE.
Implantation and intermediate-term follow-up of stents in congenital heart
disease. Circulation
1993;88:605-614[Abstract/Free Full Text]
-
Fogelman R, Nykanen D, Smallhorn JF. Endovascular stents in the
pulmonary circulation: clinical impact on management and medium-term
follow-up. Circulation
1995;92:881-885[Abstract/Free Full Text]
-
Ing FF, Grifka RG, Nihill MR, et al. Repeat dilatation of
intravascular stents in congenital heart defects. Circulation
1995;92:893-897[Abstract/Free Full Text]
-
Pinzon JL, Burrows PE, Benson LN, et al. Repair of coarctation of
the aorta in children: postoperative morphology. Radiology
1991;180:199-203[Abstract/Free Full Text]
-
Dake MW, Miller DC, Semba CP, Mitchell RS, Walker PJ, Liddell RP.
Transluminal placement of endovascular stent-grafts for the treatment of
descending thoracic aortic aneurysms. N Engl J Med
1994;331:1729-1734[Abstract/Free Full Text]
-
Blum U, Langer M, Spillner G, et al. Abdominal aortic aneurysms:
preliminary technical and clinical results with transfemoral placement of
endovascular self-expanding stent-grafts. Radiology
1996;198:25-31[Abstract/Free Full Text]
-
Furui S, Sawada S, Kuramoto K, et al. Gianturco stent placement in
malignant caval obstruction: analysis of factors for predicting the outcome. Radiology
1995;195:147-152[Abstract/Free Full Text]
-
Murphy KD, Richter GM, Henry M, Encarnacion CE, Le VA, Palmaz JC.
Aortoiliac aneurysms: management with endovascular stent-graft placement. Radiology
1996;198:473-480[Abstract/Free Full Text]
-
Krysl J, Vesely TM. Stent graft for treatment of an abdominal
aortic aneurysm: leak detected by CT. AJR
1995;165:659-661[Free Full Text]
-
Chopra S, Ghiatas AA, Encarnacion CE, et al. Transjugular
intrahepatic portosystemic shunts: assessment with helical CT angiography. Radiology
1997;202:277-280[Abstract/Free Full Text]
-
Silverman PM, Brown B, Wray H, et al. Optimal contrast enhancement
of the liver using helical (spiral) CT: value of SmartPrep. AJR
1995;164:1169-1171[Free Full Text]
-
Kuszyk BS, Fishman EK. Technical aspects of CT angiography. Semin Ultrasound CT MR
1998;19:383-393[Medline]
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Abstract
Introduction
