DOI:10.2214/AJR.08.1365
AJR 2009; 192:515-524
© American Roentgen Ray Society
MDCT Angiography of Thoracic Aorta Endovascular Stent-Grafts: Pearls and Pitfalls
Jenny K. Hoang1,
Santiago Martinez and
Lynne M. Hurwitz
1 All authors: Department of Radiology, Division of Cardiothoracic Imaging, Duke
University Medical Center, Box 3808, Erwin Rd., Durham, NC 27710.
Received June 7, 2008;
accepted after revision August 19, 2008.
Address correspondence to J. K. Hoang
(jenny.hoang{at}duke.edu).
CME
This article is available for CME credit.
See
www.arrs.org
for more information.
Abstract
OBJECTIVE. The objective of our study was to review expected
findings and complications after thoracic endovascular aortic repair on CT
angiography (CTA).
CONCLUSION. Luminal and extraluminal changes to the thoracic aorta
occur after endovascular stent-grafting. The radiologist can facilitate
appropriate management by detecting and differentiating expected CTA findings
from complications.
Keywords: aortic surgery • CT angiography • endovascular stent-grafts • postoperative complications • thoracic aorta
Introduction
In the past decade, thoracic endovascular aortic repair has gained
popularity as a less invasive alternative to open surgery for the management
of descending thoracic aortic disease. For evaluation of the postoperative
aorta, CT angiography (CTA) is frequently used to assess thoracic endovascular
aortic repair appearances and complications. In this article we describe the
pertinent normal and abnormal CTA findings the radiologist should recognize
after endovascular stent-grafting of the thoracic aorta.
Imaging Technique
Unenhanced and arterial phase contrast-enhanced CTA images of the thoracic
aorta allow assessment of the stent-graft, the excluded aortic lumen, and
complications such as endoleaks. Adding contrast-enhanced delayed phase CTA
has been shown to improve visualization of endoleaks, but it will result in an
overall higher radiation dose
[1]. Cardiac-gated CTA
techniques may be of benefit when there are suspected complications involving
the aortic valve, aortic sinus, or coronary arteries.
The use of a workstation capable of 3D multiplanar reconstructions is
important for assessing and measuring the postoperative thoracic aorta.
Obtaining axial images alone can be a pitfall because measurements of the
aorta can vary between scans depending on patient position and breathing.
Axial images can also overestimate the size of the obliquely orientated
ascending aorta and aortic arch. A 3D workstation can help to produce true
transverse plane measurements that are more accurately reproducible on
follow-up examinations. The 3D workstation is also valuable for interpreting
complicated anatomy and communicating the findings to clinicians.
CTA is a noninvasive imaging technique that has replaced conventional
angiography in many settings for the postoperative evaluation of the thoracic
aorta. Compared with MR angiography, CTA is quicker to perform and has
superior spatial resolution. However, MR angiography is a technique without
ionizing radiation, which is an important advantage for young patients and
those requiring frequent imaging.
Indications for Endovascular Stent
Thoracic endovascular aortic repair has been performed for a wide range of
descending thoracic aortic diseases, including aortic aneurysms, acute and
chronic descending thoracic aortic dissection, penetrating ulcer, intramural
hematoma, and traumatic aortic rupture. Definite indications for intervention
are aortic rupture or symptomatic aortic disease. For asymptomatic patients
with a thoracic aneurysm, the decision to intervene is complex; clinicians
must consider the operative risk versus the risk of rupture or death without
treatment. Surgery is advocated if the diameter is 5.5 cm or twice the
diameter of the normal contiguous aorta
[2,
3]. The choice between thoracic
endovascular aortic repair and open surgery remains controversial and has yet
to be investigated in randomized control trials to our knowledge. Factors
affecting the feasibility of thoracic endovascular aortic repair are aneurysm
morphology, aneurysm extent, suitability of landing zones, and operator
experience.
Although best suited to the descending aorta, thoracic endovascular aortic
repair can be extended to the aortic arch with or without open reconstruction
surgery of the aortic arch. Endovascular stents have also been used in
combination with thoracic aorta open surgery—for example, the elephant
trunk procedure, which is a two-stage procedure for diffuse aortic disease
that involves open repair of the ascending aorta and subsequent thoracic
endovascular aortic repair or open repair of the descending aorta.
Normal Endovascular Stent
Stent prostheses are composed of an inner metallic skeleton covered by an
impermeable polyester graft membrane
[4]. On CTA the metallic
framework is easily visualized as a metal-density tubular device surrounded by
the diseased aorta and adherent to the wall of normal aorta at both ends of
the stent. The covering membrane component of the stent-graft is not seen on
CTA, but it is bordered by circumferential metallic rings at the edges of the
metallic stent (Fig. 1C). The
stent-graft position and morphology are best visualized along the long axis in
the reformatted sagittal oblique plane. Additional post-processing techniques
using a wide window width (> 500 HU) and maximum-intensity-projection (MIP)
images improve visualization of the detail of metallic stents.
View larger version (165K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 1C —69-year-old man with stent-graft intentionally occluding left
subclavian artery (LSA) for treatment of distal arch aortic pseudoaneurysm.
Sagittal oblique reformatted CTA maximum-intensity-projection reformatted
image obtained with wide window width shows metallic detail of stent. Covered
component of stent is bordered by circumferential metallic rings
(arrows).
|
|
When the stent-graft is correctly positioned, the diseased portion of the
aorta is covered and excluded from the systemic circulation. For treatment of
aortic dissection, it is most important to cover the entry tear (proximal
split in the intimal flap), which not only will provide protection from aortic
rupture and promote thrombosis of the false lumen, but also will eliminate the
risk of malperfusion to branch vessels resulting from dynamic true lumen
collapse.
Pitfalls of Normal Stents
Immediately after thoracic endovascular aortic repair, CTA may show aortic
wall thickening; low-density periaortic fluid; pleural effusions, which are
more common on the left; and lower lobe atelectasis
[5,
6] (Fig.
2A,
2B). These findings are
postulated to be reactive changes to the stent polyester membrane material and
commonly resolve within 8 weeks
[6,
7]. The periaortic fluid and
aortic wall thickening should not be mistaken for intramural hematoma or
aortic rupture, which are of higher attenuation (> 40 HU).
View larger version (74K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 2A —59-year-old woman with Takayasu arteritis has expected
periaortic fluid and pleural effusion early after stent-grafting for treatment
of descending thoracic aortic aneurysm. AA = ascending aorta, DA = descending
thoracic aorta. Axial CT angiography (CTA) image obtained before thoracic
endovascular aortic repair shows aneurysm of descending aorta and diffuse
mural thickening of aorta (arrowheads). Small left pleural effusion
is seen.
|
|
View larger version (87K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 2B —59-year-old woman with Takayasu arteritis has expected
periaortic fluid and pleural effusion early after stent-grafting for treatment
of descending thoracic aortic aneurysm. AA = ascending aorta, DA = descending
thoracic aorta. Axial CTA image obtained 3 weeks after thoracic endovascular
aortic repair shows focal periaortic fluid (arrows) that is separate
from both enlarging left pleural effusion and low-attenuation excluded
aneurysm sac (asterisk). Mural thickening of aorta
(arrowhead) is unchanged.
|
|
The overall size of the aorta after stent-grafting should be similar to or
smaller than the original diseased aorta. A slight increase in the diameter of
the aneurysmal sac or false lumen, termed "excluded aortic lumen,"
on the first postoperative CTA examination is an expected finding. If there is
no evidence of endoleak, patients are managed conservatively
[6] (Fig.
3A,
3B,
3C,
3D). Second, perceived aortic
enlargement on axial images compared with preoperative CTA images may occur
because of the rigidity of the stent altering the position and angulation of
the aorta. Multiplanar reformatted images will help to accurately determine
the true size of the aorta by allowing direct cross-sectional measurements to
be taken.
View larger version (94K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 3A —59-year-old man with uncomplicated aortic enlargement after
stent-grafting for aneurysm and chronic type B aortic dissection (Stanford
Classification: Type A is any dissection that involves aorta proximal to
origin of left subclavian artery, regardless of distal extent. Type B is
dissection confined to descending aorta). Axial CT angiography (CTA) image
obtained before stent-grafting shows aneurysm and dissection in aortic arch
with visualization of intima defect (arrowhead).
|
|
View larger version (101K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 3B —59-year-old man with uncomplicated aortic enlargement after
stent-grafting for aneurysm and chronic type B aortic dissection (Stanford
Classification: Type A is any dissection that involves aorta proximal to
origin of left subclavian artery, regardless of distal extent. Type B is
dissection confined to descending aorta). Axial CTA image obtained 3 months
after thoracic endovascular aortic repair shows slight increase in diameter of
false lumen (arrows). Configuration and course of true lumen
(asterisks) have been altered with placement of rigid
stent-graft.
|
|
View larger version (82K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 3C —59-year-old man with uncomplicated aortic enlargement after
stent-grafting for aneurysm and chronic type B aortic dissection (Stanford
Classification: Type A is any dissection that involves aorta proximal to
origin of left subclavian artery, regardless of distal extent. Type B is
dissection confined to descending aorta). Axial (C) and sagittal
oblique (D) CTA images obtained after thoracic endovascular aortic
repair show pressure sensor device (arrows) in aortic arch that gave
decreasing pressure readings despite initial mild increase in size of false
lumen. Patient remained stable with conservative management. Subsequent CTA
images (not shown) depicted size of aorta unchanged.
|
|
View larger version (141K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 3D —59-year-old man with uncomplicated aortic enlargement after
stent-grafting for aneurysm and chronic type B aortic dissection (Stanford
Classification: Type A is any dissection that involves aorta proximal to
origin of left subclavian artery, regardless of distal extent. Type B is
dissection confined to descending aorta). Axial (C) and sagittal
oblique (D) CTA images obtained after thoracic endovascular aortic
repair show pressure sensor device (arrows) in aortic arch that gave
decreasing pressure readings despite initial mild increase in size of false
lumen. Patient remained stable with conservative management. Subsequent CTA
images (not shown) depicted size of aorta unchanged.
|
|
Although thoracic endovascular aortic repair is used predominantly for
descending thoracic aortic disease, in some cases the stent will extend into
the distal aortic arch and intentionally cover, partially or completely, the
left subclavian artery (LSA) (Fig.
1A,
1B,
1C). Thoracic endovascular
aortic repair coverage of the LSA is performed to achieve a minimum 2-cm
length of nondiseased aorta for stent anchorage. When the origin of the LSA is
occluded by the stent, retrograde flow from the left vertebral artery provides
perfusion of the left arm, and most cases do not require a left
carotid–subclavian bypass
[8,
9].
View larger version (103K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 1A —69-year-old man with stent-graft intentionally occluding left
subclavian artery (LSA) for treatment of distal arch aortic pseudoaneurysm.
Axial CT angiography (CTA) image before treatment shows partially thrombosed
pseudoaneurysm (arrow) in distal aortic arch.
|
|
View larger version (172K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 1B —69-year-old man with stent-graft intentionally occluding left
subclavian artery (LSA) for treatment of distal arch aortic pseudoaneurysm.
Sagittal oblique reformatted CTA image shows stent-graft extending from distal
aortic arch to descending thoracic aorta. LSA, which is nonenhancing and
expanded, is covered by stent to maximize length of stent landing zone. BCA =
brachiocephalic artery.
|
|
The EndoSure (CardioMEMS, Inc.) wireless aortic pressure sensor device is a
1.5- to 2-cm-long metallic linear device that can be mistaken for retained
surgical material or breakdown of the thoracic endovascular aortic repair if
not correctly recognized. It is placed within the excluded aortic lumen at the
time of thoracic endovascular aortic repair using an endovascular approach.
The device is deployed after stent placement without attachment (Figs.
3A,
3B,
3C,
3D and
4A,
4B). Once the device is inside
the patient, pressure measurements of the excluded aortic lumen can be made
wirelessly from outside the body using radiofrequency technology.
View larger version (96K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 4A —84-year-old woman with malpositioned pressure sensor device
after thoracic endovascular aortic repair for treatment of descending thoracic
aortic aneurysm. AA = ascending aorta, DA = descending thoracic aorta. Axial
(A) and sagittal oblique (B) CT angiography images show
malpositioned pressure sensor device (arrows) located posterior to
stent-graft and distant from anteriorly located aneurysmal sac
(asterisk, B). Pressure sensor is wedged between stent-graft
and aortic wall. Pressure monitor readings, measuring systemic pressures
transmitted from stented aorta, were erroneously high because of location of
pressure sensor device.
|
|
View larger version (153K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 4B —84-year-old woman with malpositioned pressure sensor device
after thoracic endovascular aortic repair for treatment of descending thoracic
aortic aneurysm. AA = ascending aorta, DA = descending thoracic aorta. Axial
(A) and sagittal oblique (B) CT angiography images show
malpositioned pressure sensor device (arrows) located posterior to
stent-graft and distant from anteriorly located aneurysmal sac
(asterisk, B). Pressure sensor is wedged between stent-graft
and aortic wall. Pressure monitor readings, measuring systemic pressures
transmitted from stented aorta, were erroneously high because of location of
pressure sensor device.
|
|
Complications
Collapse
Predisposing factors leading to stent-graft collapse are poor stent
attachment and oversizing of the stent. CTA findings of stent collapse are
narrowing of the endoluminal stent diameter and loss of contact of the side of
the stent with the aortic wall (Fig.
5A,
5B,
5C). Stent-graft collapse
requires urgent intervention when there is significant narrowing of the aortic
lumen.
View larger version (72K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 5A —59-year-old woman with stent collapse after thoracic
endovascular aortic repair for penetrating atherosclerotic ulcer. Axial
(A), sagittal oblique (B), and coronal (C) CT angiography
images show that medial aspect of proximal stent-graft (arrows) is
displaced to lie within lumen of aorta causing significant narrowing of
stented lumen (asterisk, A and C) is significant.
Stent-graft collapse was treated with placement of uncovered stent over
collapse and balloon expansion.
|
|
View larger version (170K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 5B —59-year-old woman with stent collapse after thoracic
endovascular aortic repair for penetrating atherosclerotic ulcer. Axial
(A), sagittal oblique (B), and coronal (C) CT angiography
images show that medial aspect of proximal stent-graft (arrows) is
displaced to lie within lumen of aorta causing significant narrowing of
stented lumen (asterisk, A and C) is significant.
Stent-graft collapse was treated with placement of uncovered stent over
collapse and balloon expansion.
|
|
View larger version (107K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 5C —59-year-old woman with stent collapse after thoracic
endovascular aortic repair for penetrating atherosclerotic ulcer. Axial
(A), sagittal oblique (B), and coronal (C) CT angiography
images show that medial aspect of proximal stent-graft (arrows) is
displaced to lie within lumen of aorta causing significant narrowing of
stented lumen (asterisk, A and C) is significant.
Stent-graft collapse was treated with placement of uncovered stent over
collapse and balloon expansion.
|
|
Migration
Stent-graft migration occurs because of poor attachment of the stent to the
aortic wall. On CTA, migration of the stent is best detected by comparing the
distance of the proximal margin of the stent relative to a fixed reference
such as the origin of the LSA. This distance is best evaluated on sagittal
oblique images.
Endoleak
The incidence of endoleak after thoracic endovascular aortic repair is
reported to be as much as 29%
[10]. Endoleaks are defined as
persistent blood flow in the excluded aortic lumen that can result in
continued pressure and enlargement of the aorta. Five types of endoleaks have
been described.
Type I endoleaks account for 40% of all endoleaks involving the thoracic
aorta [10]. These endoleaks
result from incomplete seal of the ends of the stent to the aortic wall
(Fig. 6). Treatment involves
stabilizing the stent attachment by extending the total stent coverage with an
additional stent [10]. Similar
to type I endoleak is "bird-beaking" of the proximal stent due to
incomplete apposition of the stent to the lesser curvature of the aortic arch
(Fig. 7A,
7B,
7C,
7D). In contrast to type I
endoleak, there is no enhancement of the excluded aortic lumen and treatment
is usually conservative. Continued monitoring, however, has been advocated to
assess for progression to a true type I endoleak or stent-graft collapse
[2].
View larger version (110K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 6 —71-year-old man with type I endoleak after thoracic
endovascular aortic repair for type A aortic dissection. Axial CT angiography
image shows contrast material accumulation in false lumen
(arrowheads) and direct communication of false lumen with native
aorta at proximal stent-graft attachment site (arrow).
|
|
View larger version (190K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 7A —65-year-old man with stent-graft "bird-beaking"
and buckling due to aortic arch curvature. LSA = left subclavian artery.
Sagittal oblique CT angiography (CTA) image obtained 3 months after thoracic
endovascular aortic repair for penetrating ulcer in descending thoracic aorta
shows new penetrating ulcer (arrow) and intramural hematoma
(arrowheads).
|
|
View larger version (153K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 7B —65-year-old man with stent-graft "bird-beaking"
and buckling due to aortic arch curvature. LSA = left subclavian artery.
Sagittal oblique maximum-intensity-projection CTA image obtained after
additional stent-grafting shows there are three overlapping stent-grafts: SG1,
SG2, and SG3. Original stent, SG1, is in distal descending thoracic aorta
(white arrows). SG1 is overlapped by longer SG2 (black
arrows), which extends from distal aortic arch to descending thoracic
aorta. At aortic arch, SG3 (white arrowheads) overlaps SG2 and covers
left subclavian artery. Dissection developed during procedure requiring
coiling of false lumen (black arrowheads) and LSA.
|
|
View larger version (111K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 7C —65-year-old man with stent-graft "bird-beaking"
and buckling due to aortic arch curvature. LSA = left subclavian artery. Axial
CTA image shows component of stent-graft projected in lumen of distal aortic
arch (arrow) that is concerning for stent collapse.
|
|
View larger version (178K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 7D —65-year-old man with stent-graft "bird-beaking"
and buckling due to aortic arch curvature. LSA = left subclavian artery.
Sagittal oblique CTA image shows that SG3 is buckled and protrudes into aortic
lumen (arrow) at its junction with SG2. In addition, SG3 does not
directly appose lesser curve of aortic arch (arrowhead), resulting in
"bird-beaking." Both findings are due to curvature of aortic arch
limiting close apposition of stent-graft to aortic wall.
|
|
Type II endoleaks are caused by retrograde flow of blood into the excluded
aortic lumen from patent branch vessels of the aorta. In subgroup type IIA
endoleaks, one branch vessel can be detected. In the more complex type IIB
endoleaks, flow can be seen through two or more branch vessels. These feeding
vessels include bronchial and intercostal arteries, a patent ductus
arteriosus, and the subclavian arteries. On CTA, a type II endoleak is
suspected when a focal collection of contrast material is peripherally located
in the excluded lumen. This CTA finding should prompt the radiologist to
search carefully for one or more feeding vessels. If both the feeding artery
and enhancement of the excluded lumen are small, patients can be managed
conservatively, often with spontaneous resolution after 6 months
[11] (Fig.
8A,
8B). In contrast, intervention
with embolization of the feeding vessel is required if the feeding vessel is
large, significant contrast enhancement of the excluded aortic lumen is seen,
or the excluded aortic lumen shows progressive enlargement (Figs.
9A,
9B,
9C,
10A,
10B,
10C,
11A,
11B).
View larger version (106K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 8A —32-year-old woman with type II endoleak after thoracic
endovascular aortic repair for descending thoracic aortic aneurysm due to
Marfan syndrome. AA = ascending aorta, DA = descending thoracic aorta. Axial
(A) and coronal oblique (B) maximum-intensity-projection CT
angiography images show contrast material accumulation in periphery of
aneurysmal sac (arrowheads). Small enhancing intercostal arteries
(arrows) directly communicate with this area of focal contrast
material accumulation.
|
|
View larger version (156K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 8B —32-year-old woman with type II endoleak after thoracic
endovascular aortic repair for descending thoracic aortic aneurysm due to
Marfan syndrome. AA = ascending aorta, DA = descending thoracic aorta. Axial
(A) and coronal oblique (B) maximum-intensity-projection CT
angiography images show contrast material accumulation in periphery of
aneurysmal sac (arrowheads). Small enhancing intercostal arteries
(arrows) directly communicate with this area of focal contrast
material accumulation.
|
|
View larger version (92K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 9A —48-year-old man with type II endoleak from left subclavian
artery (LSA) after thoracic endovascular aortic repair for type A dissection.
Axial CT angiography (CTA) image shows contrast material accumulation
(arrow) in excluded false lumen (asterisk).
|
|
View larger version (156K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 9B —48-year-old man with type II endoleak from left subclavian
artery (LSA) after thoracic endovascular aortic repair for type A dissection.
Sagittal oblique (B) and coronal oblique (C)
maximum-intensity-projection CTA images show contrast material accumulation
(arrows) in false lumen (asterisks) directly communicates
with LSA. Coils in LSA are from previous failed embolization
(arrowheads). Patient underwent successful embolization of false
lumen of thoracic ascending aortic dissection with resolution of endoleak (not
shown).
|
|
View larger version (155K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 9C —48-year-old man with type II endoleak from left subclavian
artery (LSA) after thoracic endovascular aortic repair for type A dissection.
Sagittal oblique (B) and coronal oblique (C)
maximum-intensity-projection CTA images show contrast material accumulation
(arrows) in false lumen (asterisks) directly communicates
with LSA. Coils in LSA are from previous failed embolization
(arrowheads). Patient underwent successful embolization of false
lumen of thoracic ascending aortic dissection with resolution of endoleak (not
shown).
|
|
View larger version (99K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 10A —50-year-old man with progressively enlarging false lumen due
to endoleak after thoracic endovascular aortic repair for type B aortic
dissection. AA = ascending aorta, DA = descending thoracic aorta. Axial CT
angiography (CTA) image obtained 3 days after thoracic endovascular aortic
repair shows persistently enhancing false lumen external to stent-graft
(asterisk).
|
|
View larger version (94K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 10B —50-year-old man with progressively enlarging false lumen due
to endoleak after thoracic endovascular aortic repair for type B aortic
dissection. AA = ascending aorta, DA = descending thoracic aorta. Axial CTA
image obtained 4 weeks after thoracic endovascular aortic repair shows
enlarging and persistently enhancing false lumen (asterisk). Source
of endoleak was left subclavian artery (LSA) (not shown).
|
|
View larger version (89K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 10C —50-year-old man with progressively enlarging false lumen due
to endoleak after thoracic endovascular aortic repair for type B aortic
dissection. AA = ascending aorta, DA = descending thoracic aorta. Axial CTA
image obtained 4 months after thoracic endovascular aortic repair and ligation
of LSA shows that false lumen is no longer enhancing, but continues to enlarge
(arrowhead) and now causes mass effect and deformity of stent-graft
(arrow). Open repair of descending thoracic aorta was subsequently
performed.
|
|
View larger version (96K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 11A —49-year-old man with type II endoleak from aberrant right
subclavian artery (RSA) after thoracic endovascular aortic repair for chronic
type B dissection. Ao Arch = aortic arch, LBV = left brachiocephalic vein, RBV
= right brachiocephalic vein, SVC = superior vena cava. Axial oblique
(A) and axial (B) CT angiography images show contrast material
accumulation in false lumen (arrowheads) communicating with aberrant
RSA. Dissection involves RSA (arrow, A).
|
|
View larger version (101K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 11B —49-year-old man with type II endoleak from aberrant right
subclavian artery (RSA) after thoracic endovascular aortic repair for chronic
type B dissection. Ao Arch = aortic arch, LBV = left brachiocephalic vein, RBV
= right brachiocephalic vein, SVC = superior vena cava. Axial oblique
(A) and axial (B) CT angiography images show contrast material
accumulation in false lumen (arrowheads) communicating with aberrant
RSA. Dissection involves RSA (arrow, A).
|
|
Type III endoleaks are caused by junctional dehiscence or device
degeneration. Junctional dehiscence results from a defect between two adjacent
or overlapping stents and occurs early after technically complex stent
procedures (Fig. 12A,
12B). Mechanical device
failure from metallic fracture or fabric wear is a later finding (average, 24
months) [12]. Type III
endoleaks are treated with placement of an additional stent.
View larger version (144K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 12A —75-year-old man with type III endoleak after emergent
thoracic endovascular aortic repair for ruptured aneurysm. Axial CT
angiography (CTA) image shows contrast material accumulation in aneurysmal sac
(arrows) surrounding stent-graft.
|
|
View larger version (182K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 12B —75-year-old man with type III endoleak after emergent
thoracic endovascular aortic repair for ruptured aneurysm. Coronal oblique CTA
image shows contrast material accumulation in aneurysmal sac (arrows)
localized around junction of two stent-grafts (arrowhead). Patient
continued to have chest pain and enlarging aneurysmal sac and eventually
underwent open repair of descending thoracic aneurysm.
|
|
Type IV endoleaks result from the porosity of the stent used for thoracic
endovascular aortic repair, leading to a blush of contrast material across the
stent. These endoleaks have been shown on conventional aortography, but have
not, to our knowledge, been reported on CTA.
Type V endoleaks, or endotension, are defined as an increase in the size of
the excluded aortic lumen without enhancement of the excluded lumen.
Postulated causes include ultrafiltration of blood across the stent-graft;
thrombus in the sac providing an ineffective barrier to pressure transmission;
and occult type I, II, or III endoleak
[13,
14]. Type V endoleak in the
thoracic aorta has been successfully treated with additional stents
[14].
When thoracic endovascular aortic repair is performed for dissection,
contrast material in the excluded lumen can also indicate that the entry or
reentry intimal tears have not been covered. Entry and reentry tears are
defined as the most proximal and distal splits in the intimal flap,
respectively. Coverage of the reentry tear is desirable but is not as critical
as coverage of the entry tear. Gradual depressurizing and shrinkage of the
false lumen can still occur if there is low retrograde flow through the
reentry tear.
Pseudoaneurysm or Dissection
New disruption of the aortic wall resulting in pseudoaneurysm or dissection
has been reported after thoracic endovascular aortic repair. This complication
results from direct trauma to the intima by the stent
[15] (Figs.
7A,
7B,
7C,
7D and
13A,
13B,
13C,
13D).
View larger version (173K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 13A —69-year-old woman with acute type A dissection developing
after thoracic endovascular aortic repair for descending thoracic aortic
aneurysm. Sagittal oblique CT angiography (CTA) image before treatment shows
atherosclerotic fusiform aneurysms of descending thoracic aorta
(arrowheads). Small penetrating atherosclerotic ulcer in descending
thoracic aorta (arrow) is seen.
|
|
View larger version (174K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 13B —69-year-old woman with acute type A dissection developing
after thoracic endovascular aortic repair for descending thoracic aortic
aneurysm. Sagittal oblique CTA image obtained immediately after thoracic
endovascular aortic repair shows new retrograde dissection (arrows)
from proximal stent-graft extending to aortic root. Dissection is also present
in left subclavian artery (LSA) (arrowhead).
|
|
View larger version (110K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 13C —69-year-old woman with acute type A dissection developing
after thoracic endovascular aortic repair for descending thoracic aortic
aneurysm. Axial CTA images show dissection involving aortic arch and root
(arrows). Patient underwent emergent open repair of ascending aorta
and aortic valve. AA = ascending aorta, DA = descending thoracic aorta.
|
|
View larger version (104K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 13D —69-year-old woman with acute type A dissection developing
after thoracic endovascular aortic repair for descending thoracic aortic
aneurysm. Axial CTA images show dissection involving aortic arch and root
(arrows). Patient underwent emergent open repair of ascending aorta
and aortic valve. AA = ascending aorta, DA = descending thoracic aorta.
|
|
Other Complications
The extravascular structures of the thorax should be routinely assessed to
look for possible postprocedural complications, including pneumonia and
pulmonary embolus. If the CTA examination includes the abdomen, other relevant
findings include access-related complications and peripheral embolus to the
solid organs.
Conclusion
Luminal and extraluminal changes to the thoracic aorta occur after thoracic
endovascular aortic repair. The radiologist can facilitate appropriate
clinical management by detecting and differentiating expected CTA findings
from complications.
References
- Iezzi R, Cotroneo AR, Filippone A, et al. Multidetector CT in
abdominal aortic aneurysm treated with endovascular repair: are unenhanced and
delayed phase enhanced images effective for endoleak detection?
Radiology 2006;241
: 915–921[Abstract/Free Full Text]
- Svensson LG, Kouchoukos NT, Miller DC, et al.; Society of Thoracic
Surgeons Endovascular Surgery Task Force. Expert consensus document on the
treatment of descending thoracic aortic disease using endovascular
stent-grafts. Ann Thorac Surg 2008;85
[suppl 1]:S1
–S41[Abstract/Free Full Text]
- Kouchoukos NT, Dougenis D. Surgery of the thoracic aorta.
N Engl J Med 1997;336
:1876
–1888[Free Full Text]
- Iezzi R, Cotroneo AR, Marano R, Filippone A, Storto ML.
Endovascular treatment of thoracic aortic diseases: follow-up and
complications with multi-detector computed tomography angiography.
Eur J Radiol 2008;65
: 365–376[CrossRef][Medline]
- Ishida M, Kato N, Hirano T, Shimono T, Shimpo H, Takeda K. Thoracic
CT findings following endovascular stent-graft treatment for thoracic aortic
aneurysm. J Endovasc Ther 2007;14
: 333–341[CrossRef][Medline]
- Sakai T, Dake MD, Semba CP, et al. Descending thoracic aortic
aneurysm: thoracic CT findings after endovascular stent-graft placement.
Radiology 1999;212
: 169–174[Abstract/Free Full Text]
- Schürmann K, Vorwerk D, Bücker A, et al. Peri-graft
inflammation due to Dacron-covered stent-grafts in sheep iliac arteries:
correlation of MR imaging and histopathologic findings.
Radiology 1997;204
: 757–763[Abstract/Free Full Text]
- Caronno R, Piffaretti G, Tozzi M, Lomazzi C, Rivolta N, Castelli P.
Intentional coverage of the left subclavian artery during endovascular stent
graft repair for thoracic aortic disease. Surg Endosc2006; 20:915
–918[CrossRef][Medline]
- Riesenman PJ, Farber MA, Mendes RR, Marston WA, Fulton JJ, Keagy
BA. Coverage of the left subclavian artery during thoracic endovascular aortic
repair. J Vasc Surg 2007;45
: 90–94; discussion
94–95[CrossRef][Medline]
- Parmer SS, Carpenter JP, Stavropoulos SW, et al. Endoleaks after
endovascular repair of thoracic aortic aneurysms. J Vasc
Surg 2006; 44:447
–452[CrossRef][Medline]
- Nienaber CA, Kische S, Ince H. Thoracic aortic stent-graft devices:
problems, failure modes, and applicability. Semin Vasc
Surg 2007; 20:81
–89[CrossRef][Medline]
- Jacobs TS, Won J, Gravereaux EC, et al. Mechanical failure of
prosthetic human implants: a 10-year experience with aortic stent graft
devices. J Vasc Surg 2003;37
: 16–26[CrossRef][Medline]
- Veith FJ, Baum RA, Ohki T, et al. Nature and significance of
endoleaks and endotension: summary of opinions expressed at an international
conference. J Vasc Surg 2002;35
:1029
–1035[CrossRef][Medline]
- Zimpfer D, Schoder M, Gottardi R, et al. Treatment of type V
endoleaks by endovascular redo stent-graft placement. Ann Thorac
Surg 2007; 83:664
–666[Abstract/Free Full Text]
- Lopera J, Patino JH, Urbina C, et al. Endovascular treatment of
complicated type-B aortic dissection with stent-grafts: midterm results.
J Vasc Interv Radiol 2003;14
: 195–203[Medline]
CiteULike 
Complore 
Connotea 
Del.icio.us 
Digg 
Reddit 
Technorati What's this?
Top
Abstract
Introduction
