Download Imaging of the Postsurgical Thoracic Aorta

SA-CME ARTICLE
Imaging of the Postsurgical Thoracic Aorta
A State-of-the-Art Review
Larry A. Latson, Jr, MD, MS,*w Abe DeAnda, Jr, MD,z and Jane P. Ko, MD*
Abstract: Techniques for repair of the aorta currently include open
and endovascular methods, hybrid approaches, minimally-invasive
techniques, and aortic branch vessel reimplantation or bypass.
Collaboration among radiologists and vascular and cardiothoracic
surgeons is essential. An awareness of the various surgical techniques, expected postoperative appearance, and potential complications is essential for radiologists. This review will cover the postoperative appearance of the thoracic aorta with a focus on the
ascending aorta. The value of three-dimensional image evaluation
will also be emphasized.
Key Words: postoperative, computed tomography, thoracic aorta,
aneurysm, dissection, dual energy, high pitch, endovascular repair
(J Thorac Imaging 2016;00:000–000)
LEARNING OBJECTIVES
After completing this CME activity, physicians should
be better able to:
(1) Outline surgical and interventional techniques for aortic
repair.
(2) Identify postsurgical changes and complications resulting from aortic surgery on imaging.
(3) Describe the role of imaging in postoperative
evaluation.
(4) Apply computed tomography (CT) protocols for posttherapy evaluation of the aorta.
Surgical techniques to repair the thoracic aorta have
advanced rapidly. Radiology plays an essential role in the
follow-up of patients after aortic surgery. Diagnostic radiologists are essential members of a multidisciplinary team
comprising vascular surgeons, cardiothoracic surgeons, and
interventional radiologists. The postoperative evaluation of
these patients can be challenging given the complexity of
the surgical and endovascular procedures currently being
performed.
Therefore, our objective is to review the normal
appearance and potential complications after repair of the
thoracic aorta, focusing on open and minimally-invasive
surgical techniques. Attention will be primarily directed
toward the ascending aorta and aortic arch, open repair,
and how to minimize potential interpretive pitfalls.
THORACIC AORTIC ANATOMY
The thoracic aorta is divided into the aortic root,
ascending (tubular) aorta, the arch, and the descending
thoracic aorta.1,2 About 68% to 74% of patients have
conventional aortic arch branch vessel anatomy, and any
variations can affect surgical repair.3,4 The innominate and
left common carotid arteries arise from the arch as a
common origin (sometimes termed a “bovine” arch) in
about 21% to 27% of the population. In 3% to 7%, the left
vertebral artery arises directly from the arch. Other variants
include a left aortic arch with aberrant right subclavian
artery and a right aortic arch with either an aberrant
left subclavian artery or a mirror-image branching
configuration.3,4
IMAGING TECHNIQUES FOR POSTOPERATIVE
EVALUATION
CT Angiography: Imaging Protocol and Aortic
Measurement
CT angiography (CTA) and magnetic resonance
angiography (MRA) play a major role in evaluating the
aorta after open or endovascular treatment. Protocols
should be tailored according to the surgery performed
(Table 1). CT angiogram protocols achieve peak contrast
enhancement with either a timing run or bolus tracking.
Abdominopelvic CTA including the iliac and femoral
arteries is used to assess for access site complications in the
femoral artery, when cannulated for cardiopulmonary
bypass (CPB). With ultrafast imaging, intravenous contrast
volumes can be reduced to as low as 50 mL, followed by a
saline bolus, to decrease the risk for nephrotoxicity.5
Motion-free images are useful when evaluating the
postsurgical aorta. Ultrafast nongated techniques, such as
with dual-source or single-source wide-detector array CTs,
minimize pulsation artifacts that can mimic dissection and
hinder measurement, particularly of the ascending aorta6
(Fig. 1). Alternatively electrocardiogram (ECG)-gated
methods can be used, although they are typically associated
with higher radiation doses compared with nongated protocols. The routine use of ECG gating therefore may not be
warranted and varies among institutions.7–9 ECG-gated
From the Sections of *Thoracic Imaging; wCardiac Imaging, Department of Radiology, New York University School of Medicine, New York, NY;
and zDivision of Cardiothoracic Surgery, University of Texas Medical Branch at Galveston, Galveston, TX.
Dr Larry A. Latson, Jr, MD, MS, is an Assistant Professor of Radiology, New York University School of Medicine, New York, NY.
Dr Jane P. Ko, MD, is a Professor of Radiology, New York University School of Medicine, New York, NY.
Dr Abe DeAnda, Jr, MD, is the John T. Moore, MD Distinguished Professorship in Surgery, Professor and Chief, Cardiovascular and Thoracic
Surgery, University of Texas Medical Branch at Galveston, Galveston, TX.
The author and all staff in a position to control the content of this CME activity and their spouses/life partners (if any) have disclosed that they have
no financial relationships with, or financial interests in, any commercial organizations pertaining to this educational activity.
Correspondence to: Larry A. Latson, Jr, MD, MS, Section of Thoracic Imaging, Department of Radiology, New York University School of
Medicine, 660 1st Ave., New York, NY 10016 (e-mail: [email protected]).
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DOI: 10.1097/RTI.0000000000000246
J Thorac Imaging Volume 00, Number 00, ’’ 2016
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J Thorac Imaging
Latson et al
Volume 00, Number 00, ’’ 2016
TABLE 1. Imaging Techniques Used for Postoperative Evaluation
Potential Use
CT Technique
Delayed imaging
Identify slow endoleak
Differentiate thrombus from slow flow in false dissection lumen
Precontrast imaging
For first study after surgical or endovascular repair: for graft/stent location
For acute symptomatic presentations: better identification and characterization of acute,
intramural hematoma, particularly the ascending aorta
Dual-energy CT
Eliminates the need for precontrast imaging
“Virtual” noncontrast images: displays postsurgical graft, endovascular stent, and pledgets
Iodine-enhanced images: displays areas of iodine in an area, such as endoleaks and
pseudoaneurysms
Ultrafast imaging techniques, eg high-pitch
CT, wide detector row CT
Minimizes pulsation artifact without gating, if ascending aorta is primarily affected
ECG-gated imaging
If perivalvular leak or complications in coronary arteries are suspected
MR Technique
3D SSFP
Noncontrast free-breathing technique, can be used in patients with severe renal
dysfunction
Cine sequences
For assessment of persistent dissection flap in the descending aorta.
Evaluate for functional obstruction
Phase contrast
Measurement of aortic flow volume and velocity through a specific plane: allows
estimation of pressure gradients after coarctation repair, prolonged deceleration time in
the descending aorta, and collateral flow distal to coarctation
Postprocessing Techniques
3D volume rendering: for 3D aortic anatomy, aneurysm location and morphology, and
endovascular stent location
Centerline and/or double-oblique images: aortic dimensions and/or double-oblique views
angiogram protocols are helpful when coronary artery
complications, aortic valve anatomy, and perivalvular
abscesses and pseudoaneurysms are suspected. Prospective
ECG-gated protocols, particularly ultrafast ECG-gated
high-pitch ones, result in lower radiation exposure in
patients with low heart rates compared with retrospectively
gated techniques.10,11 Retrospective gating, however, provides information at different phases of the cardiac cycle.8
Precontrast imaging facilitates identification of postsurgical grafts, clips, or felt pledgets (Table 1).12 To limit
radiation exposure, precontrast imaging can be reserved for
the first postoperative examination and confined in the
craniocaudal direction to the surgical region. A virtual
noncontrast imaging series can be created from a postcontrast dual-energy CT using material decomposition
(Fig. 2). Dual-energy techniques entail near simultaneous
FIGURE 1. High-pitch mode to reduce motion artifact. A 69-year-old female patient being followed with serial imaging for a dilated
ascending aorta. A, Image acquired using standard pitch acquisition. B, Image acquired 1 year later, utilizing a high-pitch technique.
Note the decreased motion artifact in the wall of the ascending aorta, main pulmonary artery, and proximal coronary arteries (arrows).
Both sets of images are of 1 mm thickness, 100 kVp, using the same amount of contrast material, and were obtained without the use of
ECG-gating. The image (B) was reconstructed with iterative reconstruction, accounting for the decreased noise.
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Copyright r 2016 Wolters Kluwer Health, Inc. Unauthorized reproduction of this article is prohibited.
This paper can be cited using the date of access and the unique DOI number which can be found in the footnotes.
J Thorac Imaging
Volume 00, Number 00, ’’ 2016
Imaging of the Postsurgical Thoracic Aorta
FIGURE 2. Dual energy to generate virtual noncontrast images. A 78-year-old female patient for follow-up of ascending aortic aneurysm
with history of prior coronary artery bypass grafting and mitral and tricuspid valve repairs. Focal high attenuation adjacent to the
anterior ascending aorta was initially questioned to be a pseudoaneurysm on prior CT. Dual-energy CT image obtained during IV
contrast administration redemonstrates the finding (black arrow, A). However, the virtual noncontrast image (B) generated from
material decomposition of the CT angiogram data demonstrated the high-attenuation finding, confirming it was normal postoperative
pledget material rather than a pseudoaneurysm, near the cannulation site for cardiopulmonary bypass in the ascending aorta.
imaging with low and high tube potentials.13–16 Delayed
postcontrast imaging, performed during the venous phase
at approximately 60 to 90 seconds after beginning the
contrast injection, aids in detecting slow endoleaks and in
differentiating poor opacification of any remaining false
dissection lumen from the thrombus.16–18
Measurement is an essential part of any radiologic
assessment of the postsurgical aorta, and measurements can
vary up to 1.8 ± 1 mm between the systole and the diastole.19 The aortic lumen should be consistently measured
using the outer wall20 and acquired at the point of maximal
enlargement for each of the aortic regions. The smallest
cross-sectional measurement should be used, as a larger
dimension can result from oblique orientation of the aorta
in the axial plane. Comparison with multiple studies and
remeasurement of the aorta, rather than relying on prior
reported measures, aid in detecting changes in caliber.
Double-oblique off-axial and curved multiplanar reformats
with automated center line generation are useful, particularly for the sinus of Valsalva, to achieve measures that are
truly orthogonal to the vessel lumen.21–25 Standardized
protocols and measurement techniques at an institutional
level should be established through collaboration of radiologists and referring clinicians. It is advisable to follow-up
the patient with the same modality, whether CT or magnetic resonance imaging (MRI).26
Off-axial images in the left anterior oblique, sagittal,
and coronal planes are also essential for detecting and
evaluating aortic surgical changes and pathology, particularly in the aortic arch. Three-dimensional (3D)
maximum-intensity projection and volume-rendering techniques with varying transparencies help identify endovascular stent location and number.27
MRA
MRA can be used to evaluate the aorta without ionizing radiation (Table 1). Valvular disease and ventricular
function can be assessed at the same time. ECG gating can
be utilized concurrently to resolve the relatively small
coronary arteries and intracardiac anatomy, which are
typically obscured on conventional MRA28 (Fig. 3). Newer
techniques include unenhanced free-breathing 3D steadystate free precession MRA sequences that do not require
breath-holding and gadolinium contrast administration. A
“navigator” placed typically over the right hemidiaphragm
and dome of the liver28,29 allows imaging to occur only
when the diaphragm is at the specified level, with reported
excellent image quality.30,31 MRI is susceptible to magnetic
field inhomogeneity, and artifacts caused by metallic stents
can be minimized by optimizing the imaging parameters.32,33 Phase-contrast imaging is useful for the estimation
of any pressure gradient when coarctation is suspected. As
with CT, consistent MRA imaging and reporting protocols
are needed.
SURGICAL AND ENDOVASCULAR TECHNIQUES:
POSTOPERATIVE APPEARANCE AND
COMPLICATIONS
Aortic diseases that require repair and typical criteria
for intervention are described in Table 2.20 The type of
therapy undertaken depends on many variables including
underlying anatomy, pathophysiology of the aortic disease,
acuity of presentation, preferences of the surgeon, availability of certain devices and implants, and techniques in
practice at the time of surgery. Knowledge of open surgical
and endovascular techniques and their expected postoperative imaging appearance aids in the identification of
complications (Tables 3, 4).
Open Repair
Ascending Aorta
The ascending aorta is most often repaired using an
open surgical approach. Aneurysm is a common indication.
Operations involve either placement of an inclusion graft
within an aneurysm sac or, more commonly now, an
interposition graft replacement of the diseased aorta.
Ascending aortic grafts often terminate in the distal
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Volume 00, Number 00, ’’ 2016
FIGURE 3. A 26-year-old female patient with a history of coarctation repair as a child, with end-to-end anastomosis. An unenhanced 3D
respiratory-gated “navigator” sequence (free-breathing 3D steady-state free precession [SSFP]) MRA was obtained in an oblique sagittal
orientation without gadolinium contrast. Images demonstrate normal postcoarctation repair appearance of the aorta at the isthmus (A
and B, white arrow) on the SSFP sequence (A) and 3D volume-rendered image (B), with mild dilatation of the proximal descending
aorta just beyond the site of repair and no evidence of recoarctation or dissection. The origin of the left subclavian artery is noted (B,
white *). Importantly, this technique is both respiratory and cardiac ECG-gated and also useful in evaluating the left main coronary
artery anatomy (C, black arrow).
ascending aorta, proximal to the innominate artery. The
interposition graft is typically a coated conduit, associated
with better anastomotic results and less pseudoaneurysm
formation1,35 (Table 3 and Fig. 4). The inclusion graft
lumen is smaller than the aneurysm sac and creates a
“perigraft space” between the graft and aneurysm wall that
thromboses. A “Cabrol shunt,” a surgical connection
between the aneurysm sac and the right atrium, can be
performed to drain blood flow from the perigraft space into
the right atrium if excessive bleeding is identified during
surgery.35 Compression of the graft lumen from an
enlarging perigraft space is prevented (Fig. 5).
Associated Aortic Valve Disease: If the aortic root is
not enlarged, the ascending aortic aneurysm is repaired
with an interposition graft, and simultaneously the diseased
aortic valve is replaced with either a mechanical or a bioprosthetic aortic valve (Figs. 4, 6). The Ross procedure
4 | www.thoracicimaging.com
is another technique for aortic valve replacement in which
the patient’s own native pulmonic valve is moved into the
aortic position (autograft). A homograft valve is used
to replace the native pulmonic valve36 (Fig. 7 and Table 3).
The Ross procedure results in a living autologous
trileaflet neo-aortic valve and is often favored in younger
patients.36
Aortic Root Enlargement and Aortic Valve Disease:
Aneurysmal dilatation of both the aortic root and the
tubular ascending aorta and an abnormal aortic valve is
often addressed with a mechanical or a biological composite valved graft. Regardless of the root replacement
technique, the coronary arteries are also typically either
reimplanted or bypassed at the time of surgery, with one
exception being the Cabrol procedure described below.
First described by Wheat et al,37 aortic root replacement has evolved, with Bentall and DeBono developing an
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J Thorac Imaging
Volume 00, Number 00, ’’ 2016
Imaging of the Postsurgical Thoracic Aorta
TABLE 2. Aortic Diseases Resulting in Aortic Intervention and Suggestions for Imaging Evaluation20,26,34
Conditions
Aneurysm
Etiologies
Indications for Repair
Atherosclerotic (main cause in descending aorta)
Age-related aneurysm
Marfan’s, Turner’s, Ehler’s-Danlos, Loeys-Dietz, other connective
tissue diseases and familial aneurysm syndromes, particularly
affecting the ascending aorta
Aortic valve stenosis, including bicuspid aortic valve
Aortic valve regurgitation
Vasculitis (Takayasu’s, Giant Cell)
Size: unless other coexisting conditions
Ascending: maximal diameter
Z5.5 cm
Z4.5 cm with aortic valve disease
Aortic arch:
Z5.5 cm
< 5.5 cm if ascending and/or descending
aortic repair also planned
Descending:
Z5.5 cm
> 6 cm if thoracoabdominal
Coexisting conditions
Rapid enlargement: >5 mm/y
Complication, eg dissection, rupture
Connective tissue disease and familial
syndromes: indications for repair at smaller
sizes than the general population; require
life-long surveillance, screening of first-degree
relative
Symptomatic aneurysm
Familial syndrome
Ascending and arch: typically repaired emergently
Descending: traumatic and mycotic typically
repaired immediately; surveillance to assess for
for aortic dissection
Type A (involving ascending aorta and/or arch):
typically repaired emergently
Type B (distal to the left subclavian artery):
typically medically managed and followed with
imaging unless complications of end-organ
ischemia, pseudoaneurysm size meeting criteria
for repair, or rupture
Involving ascending and/or arch: typically
repaired emergently
Descending thoracic aorta: medically managed
and followed unless complications are identified,
such as dissection, pseudoaneurysm, rupture
Often amenable to TEVAR
Classified and treated similar to dissection and
PAU
Pseudoaneurysm
Aortic dissection, penetrating atherosclerotic ulcer (PAU), trauma,
mycotic
Aortic dissection
Intimal tear resulting in blood flow within the media (false lumen),
with subsequent weakening of the aortic wall with risk for
pseudoaneurysm and rupture
Penetrating
atherosclerotic
ulcer (PAU)
Atherosclerotic plaque with ulceration through the intima into the
media
Intramural
hematoma
(IMH)
Coarctation
Hemorrhage within the media, either through intimal tear and
thrombosis in the false lumen, thrombosed dissection lumen,
IMH related to PAU, or rupture of vasa vasorum in the media
Focal narrowing of the aorta
Generally repaired if a pressure gradient Z20 mm
Hg across the coarctation or evidence of
significant collateral flow
inclusion technique using a composite valve graft. The
coronary arteries can be either directly anastomosed to the
graft, or the coronary ostia and a small amount of native
surrounding aortic wall38 (coronary “buttons”) can be
attached to the graft in a side-to-side manner. After many
enhancements through the years,1 the term “Bentall
procedure” now often refers to replacement of the aortic
valve and root with a composite interposition graft and
anastomosis of the coronary arteries onto the graft
(Fig. 8).39 The Cabrol procedure can be performed to
address patients in whom coronary button reimplantation
is not feasible because of severe atherosclerosis of the
ascending aorta or proximal coronary arteries (Fig. 5).1,35,40
This technique involves a composite aortic root and valve
graft and a side-to-side anastomosis of a single Dacron
graft that supplies both the right and the left coronary
arteries35,39 (Fig. 5). Knowledge of this technique avoids
misinterpretation of the coronary graft as a pseudoaneurysm.
Normal Aortic Leaflets With Enlarged Aortic Root and
Annulus: Aortic root enlargement can result in aortic regurgitation, even when the valve leaflets are normal. Valvesparing root replacement techniques are useful.41 Either
remodeling of the aortic root or reimplantation of the aortic
valve can be undertaken.42 The David procedure and its many
modifications consist of reimplanting the native aortic valve
within an ascending aortic graft. The Yacoub procedure is a
remodeling technique of the sinus of Valsalva in which an
aortic graft is cut so that the individual sinuses are replaced
while leaving the valve intact.43 Both procedures require
coronary reimplantation. An excellent review of various aortic
root replacement techniques with diagrams is provided by
Prescott-Focht et al.39
Isolated Aortic Arch or Combined Aortic Arch/
Ascending Aorta: The simultaneous replacement of the
proximal arch and ascending aorta can be performed. Total
arch replacement, in combination with ascending aortic
repair, can be used to treat aortic dissections with
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J Thorac Imaging
Latson et al
Volume 00, Number 00, ’’ 2016
TABLE 3. Typical Aortic Repair Techniques According to Region Involved
Regions Involved
General Repair Techniques
Cardiopulmonary bypass:
Aorta clamped proximal to cannula
Oxygenated blood return to distal ascending aorta distal to clamp
Alternatively, oxygenated blood return to femoral artery, when aortic dissection in arch
and descending aorta
Circulatory arrest usually not needed
Tubular ascending aorta
Open surgery
Interposition graft
Inclusion graft
Cabrol shunt occasionally performed to decompress perigraft space
Tubular ascending aorta, aortic root
Open surgery
enlargement ± aortic leaflet disease
Aortic valve leaflets abnormal:
Bentall procedure
When severe atherosclerosis involves the origins of the coronary arteries or aorta
surrounding coronary artery origins: Cabrol procedure
Aortic valve leaflets without disease (ie, aortic regurgitation from dilatation of aortic
root): possibly valve-sparing surgery with coronary reimplantation:
David procedure
Yacoub procedure
Tubular ascending aorta, normal root caliber, Open surgery
aortic valve disease
Ascending aortic graft (inclusion or interposition) + aortic valve replacement, eg
Wheat procedure
Ross procedure for aortic valve replacement in young patients
Aortic Arch
Cardiopulmonary bypass:
Oxygenated blood returned to right axillary or innominate artery via cannula for
selective cerebral perfusion
Typically hypothermic circulatory arrest
Ascending aorta, proximal aortic arch
Open surgery:
Ascending aortic and proximal aortic arch graft
Great vessel reimplantation into ascending aortic graft or another great vessel branch
Aortic arch only
Open surgery:
Aortic graft and arch debranching (arch vessels reimplanted into common graft arising
from aorta)
Aortic arch and proximal descending thoracic Open surgery:
aorta
Elephant trunk procedure (arch ± ascending aortic grafting, followed by descending
aortic graft or endovascular stent (modified elephant trunk)
Descending Aorta
Cardiopulmonary bypass:
Cardiopulmonary bypass may not be needed
Oxygenated blood return to ascending aorta or right axillary artery
Circulatory arrest usually not needed
Descending thoracic aorta
Aneurysm:
Endovascular repair ± coverage of left subclavian artery
Carotid-subclavian bypass graft (if coverage of left subclavian artery) or endovascular
techniques (chimney or snorkel) to preserve flow to left subclavian
Aneurysm with chronic dissection:
Open repair (particularly in connective tissue disorders), possibly endovascular repair
Attention to maintaining spinal cord perfusion (ie, prophylactic cerebrospinal fluid
drainage)
Thoracoabdominal aorta
Typically open repair, with vascularization of end organs as needed
Attention to maintaining spinal cord perfusion
Coarctation repair
Resection of coarctation and end-to-end anastomosis or interposition graft
Patch aortoplasty
Subclavian flap aortoplasty
Stent placement: young adults, adults
Ascending Aorta
complications such as aneurysm or leakage.20 Arch repair
entails reimplantation of the great vessel(s) either onto the
native or grafted ascending aorta or onto other great
arteries, such as the innominate to the left common carotid
arteries. Aortic “debranching” refers to removal of the 3
major branches from the aortic arch and their reimplantation into a trifurcated graft that arises from the ascending
aorta (Figs. 9–11).
6 | www.thoracicimaging.com
Descending Aorta
Descending Thoracic Aorta With Aortic Arch Involvement: The aortic arch and descending aorta cannot easily be
addressed during the same surgery (Table 3). Therefore, a
2-step “elephant trunk” repair can be performed.44 First,
the aortic arch is debranched and repaired by means of a
median sternotomy. The distal end of the arch graft is left
“dangling” within the lumen of the proximal descending
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J Thorac Imaging
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Imaging of the Postsurgical Thoracic Aorta
TABLE 4. Postoperative Imaging Findings and Complications
Postoperative Imaging Appearance, Complications, and Pitfalls
Open Repair
Surgical graft
Interposition graft:
High attenuation, difficult to see on contrast CT; some barely visible on noncontrast CT
Can mimic atherosclerotic disease
Abrupt caliber change in segment of aorta indicates graft
Cabrol procedure: focal enhancement adjacent to ascending aorta related to coronary
graft to which coronary arteries anastomose
Inclusion grafts:
Thrombosed aneurysmal perigraft space, surrounding a normal-sized lumen enclosed by
graft
Can mimic aortic dissection
Mild indentations at proximal, distal anastomosis
Pledgets can indicate proximal, distal anastomosis
Dissection or intramural hematoma repair:
Dissection or intramural hematoma remains in aorta distal to graft
Aortic arch branch vessel dissections can be observed
Cabrol shunt
Small connection coursing from perigraft space to right atrium (left to right shunt,
decompressing aneurysm sac), typically thrombosed after early postoperative period, but
can persist
Can mimic thrombosed or enhancing pseudoaneurysm; coronal multiplanar reformats
helpful for evaluation
Elephant trunk procedure
Graft in the ascending aorta and arch with aortic arch debranching (see below)
Dangling end of arch graft within the lumen of the descending aorta, mimicking dissection
flap (stage I)
After stage II of repair: extension of graft more distally into the descending aorta (open or
endovascular)
Pledgets
High attenuation, at anastomoses site
Can mimic small pseudoaneurysm on contrast series; precontrast or dual-energy virtual
noncontrast imaging useful
At proximal and distal anastomosis
Aortic arch branch vessel reimplantation
Common origin of arch vessels from a common graft (arch repairs) and can be bifurcated
changes (aortic debranching)
or trifurcated
Common graft arises from below the graft in the ascending aorta or occasionally aortic
graft
Subclavian flap aortoplasty (for coarctation) Ligation of the proximal subclavian artery
and patch aortoplasty
Contour abnormality in the region of prior coarctation with subclavian flap aortoplasty
Dacron patch in the region of coarctation with patch aortoplasty
Oversewn side arms in grafts
Saccular outpouching mimicking pseudoaneurysm, however high attenuation on
precontrast imaging
Clip or pledget at cannulation sites
Complications and pitfalls
Early postoperative complications
Edema, pneumonia, acute respiratory distress syndrome
(within 30 d)
Infected collections, mycotic aneurysm: enlarged mediastinum. Saccular outpouchings of
contrast
Anastomosis breakdown - mediastinal hematoma, hemothorax: enlarged mediastinum
Foreign bodies: needles, surgical sponges with linear dense markers within
Delayed complications
Perigraft flow (inclusion graft)
Enhancement in perigraft space
Pseudoaneurysm
Cardiopulmonary cannulation sites (clips or pledgets, ascending aorta, axillary/subclavian
artery depending upon approach)
Anastomosis sites of aorta grafts, coarctation repair
Aneurysm enlargement
From perigraft flow
In areas of chronic dissection
Sternal dehiscence and infection
Change in sternal wire alignment over time
Cabrol shunt patency
Possible shunt L-R (ascending aorta to right atrium)
Infection
Low-attenuation collections, gas, aneurysm formation
Aortoesophageal and aortopulmonary
Mediastinal gas bubbles, collection, contrast extravasation
fistula
Recoarctation
Aneurysmal dilatation, ascending and descending
Acute dissection
Distal to surgical sites
Endovascular Repair
Left subclavian coverage
Endovascular stent
Graft between carotid and subclavian artery
Occlusion of proximal left subclavian artery (proximal to left vertebral artery) with
thrombus or metallic coil or surgical ligation
Radiodense metallic stent in the aorta at the site of aneurysm or coarctation
Stents in left subclavian artery to maintain patency, when TEVAR proximal to left
subclavian artery (eg, snorkel, chimney stent)
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TABLE 4. (continued)
Postoperative Imaging Appearance, Complications, and Pitfalls
Early complications
Delayed complications
Stent migration
Endoleak
Aneurysm enlargement
Dissection
Kinking, strut fractures
Paraplegia
Paraparesis, monoparesis
Carotid, vertebrobasilar strokes from embolic phenomena
Access vessel thrombosis
Back pain and leukocytosis
Renal failure
Infection, hematoma at surgical sites
Endoleak (see below)
Change in location of stent (measured relative to landmarks like origins of arch vessels)
Type I: attachment site (proximal and distal ends)
Type II: branch endoleaks (left subclavian artery, intercostal arteries)
Type III: midgraft holes, stent disruptions, modular stent disconnections
Type IV: graft porosity
Type V: endotension—progressive aneurysm enlargement without visible leak
Can be mimicked by calcification in thrombus within perigraft space (noncontrast CT
helpful)
From endoleak or endotension
Retrograde or antegrade dissection flap, detached portion of intimal flap of dissection
within lumen
Sharp stent angulation
Fragments and extraluminal extension
FIGURE 4. A 67-year-old male patient with a history of ascending aorta aneurysm after repair with an interposition graft. The proximal
and distal anastamoses of the graft create apparent “waists” in the ascending aorta (A, black arrows). On precontrast images, the graft
itself is only faintly visible as a rim of mildly high-attenuation material (B, white arrows), whereas on postcontrast images (C) the graft
appears as a rim of relative low attenuation with some calcifications in the graft material evident (C, black arrows). The overall change in
caliber of the aorta at the graft indicates its presence also. The patient is also status post bioprosthetic aortic valve replacement.
8 | www.thoracicimaging.com
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J Thorac Imaging
Volume 00, Number 00, ’’ 2016
Imaging of the Postsurgical Thoracic Aorta
FIGURE 5. A 90-year-old male patient with a history of Cabrol procedure approximately 15 years earlier, which involved aortic valve
replacement, inclusion graft repair of the ascending aorta, reimplantation of the coronary arteries from a single ostium, and creation of a
shunt between the aneurysm sac and the right atrium (“Cabrol shunt”). In this patient, the native (diseased) ascending aneurysm sac (A,
white arrows) is seen wrapped around the ascending graft. Angiographic (B) and 60-second delayed-phase images (C) show the
ascending aortic graft lumen (black *) compressed by thrombus and perigraft flow (white *) in the aneurysm sac. Contrast enhancement representing perigraft flow is seen better on the delayed images (C) than in the angiographic phase (B); the exact site of perigraft
flow origin was not identified. The patient has a thrombosed Cabrol shunt (black arrow, A and white arrow, D), which is a surgically
created fistula from the perigraft space of the aneurysm sac to the right atrium, intended to decompress the aneurysm sac in the initial
postoperative period and subsequently thrombose. The coronary arteries are supplied by a conduit with a single side-to-side anastomosis (not shown) that branches into right and left coronary artery limbs (black arrows, B and E), which are then anastomosed with the
native coronary arteries. Note the severely diseased proximal left anterior descending and left circumflex coronary arteries.
aorta. A new graft can be placed into the dangling elephant
trunk during subsequent open or endovascular treatment of
the descending aorta 45 (Figs. 9, 10).
Thoracoabdominal Aneurysm Repair: Given the length
of aorta involved, thoracoabdominal aneurysms are often
repaired with open surgery. Combined open and endovascular therapy and fenestrated endovascular grafts are
becoming more commonly used. Descending thoracic and
thoracoabdominal aortic aneurysms have been classified by
Crawford et al46 and refined by Safi and Miller47 (Table 5).
The artery of Adamkiewicz, a major source of spinal cord
perfusion, most often arises from the left 9th to 12th
intercostal artery. Therefore, Crawford Extent II aneurysms that begin beyond the left subclavian artery and
extend to the iliac bifurcation have higher rates of postoperative neurological deficits47,48 (Table 5). Spinal cord
monitoring and prophylactic cerebrospinal fluid (CSF)
drainage during open and endovascular repair have been
used to lower CSF pressure in the spinal canal and promote
spinal cord blood flow.49 However, CSF drainage is associated with its own complications that include intracranial
hypotension, subarachnoid bleeding, subdural hematoma,
epidural hematoma, and infection.48
Open Surgical Coarctation Repair: The type of repair
undertaken depends on the coarctation anatomy, the age of
the patient at the time of repair, individual preferences of the
surgeon, and the available techniques (Table 3). First successfully described in 1945,50 surgical repair includes resection
of the coarctation segment with end-to-end anastomosis
(Fig. 3) or placement of an interposition graft (Fig. 12). Other
methods include patch aortoplasty, in which a graft is used to
enlarge the aorta. Subclavian flap aortoplasty, often performed in infants and children, entails ligation of the left
subclavian artery with subsequent rotation of and use of a
flap of tissue from this vessel to expand the aortic lumen.50
Patients with known and/or repaired coarctation require lifelong follow-up, although the recommended frequency of
follow-up imaging is not yet clearly determined.34
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Latson et al
J Thorac Imaging
Volume 00, Number 00, ’’ 2016
FIGURE 6. A 20-year-old male patient with a history of Loeys-Dietz syndrome and numerous aortic valve procedures, beginning with a
Ross procedure. A subsequent bioprosthetic valve failure resulted ultimately in a mechanical aortic valve replacement. Oblique sagittal
CTA (A) demonstrates a mechanical aortic valve prosthesis with a large 7 cm aneurysm of the aortic root. Subsequently, the patient
underwent a second mechanical valve replacement and ascending aorta replacement using an interposition graft, with smaller lumen
size (B). Postrepair axial-oblique CTA image (C) demonstrates normal postoperative appearance of a mechanical aortic valve. A TEVAR in
the descending thoracic aorta is also present.
Imaging and Complications
Postoperative Appearance: Chest radiography evaluation in the postoperative patient should evaluate the size of
the mediastinum in comparison with the preoperative
examination. Graft material from open surgery is typically
not visualized, and clips on portable radiographs may not
be clearly seen. Median sternotomy wires and aortic valve
replacements can be seen. Metallic areas in bioprosthetic
valves are evident on radiography, and some mechanical
valves can be radiolucent on radiography.
Description of the aortic graft location and the presence of any bypass grafts should be performed on postoperative imaging evaluation. On contrast-enhanced CT,
the graft wall is difficult to identify because of the density of
luminal contrast. Precontrast imaging can assist in visualizing the graft, which can be only mildly radiodense and
occasionally misinterpreted as aortic wall atherosclerosis
(Fig. 4). The graft may not be visualized depending upon
the graft material. The only clues may be the presence of
sternotomy wires, mediastinal clips, changes in luminal
caliber, and small indentations and pledgets at the graft
10 | www.thoracicimaging.com
ends. Pledgets are placed to decrease bleeding at anastomosis sites and appear as high-attenuation ovoid densities
on CT (Fig. 2).
An interposition graft is often of smaller luminal diameter than the adjacent native aorta. This leads to an
abrupt caliber change, particularly in the ascending aorta.
Proximal and distal graft anastomoses can appear as small
indentations or waists, best identified on coronal or sagittal
reformats (Figs. 4, 8, 12).
In the inclusion graft procedure, the graft is located
within the aneurysm sac, and therefore the caliber of the
aorta remains aneurysmal (Fig. 5, Tables 3 and 4). The
perigraft space, formed between the aneurysm sac and the
graft, should be thrombosed. In the early postoperative
phase, acute hematoma within the perigraft space has high
attenuation and gradually becomes isodense.
In the Cabrol procedure, comprising a valved inclusion graft and a coronary artery conduit for coronary
reimplantation,35 the coronary conduit is positioned adjacent to the ascending aorta (Fig. 5). A Cabrol shunt placed
at the time of surgery for drainage and decompression of
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Volume 00, Number 00, ’’ 2016
Imaging of the Postsurgical Thoracic Aorta
FIGURE 7. A 19-year-old man with a history of congenital aortic valve insufficiency. The patient had a history of a Ross procedure 1 year
earlier, with placement of the patient’s native pulmonary valve in the aortic valve position (autograft) and a pulmonary valve homograft.
A pseudoaneurysm of the left ventricular outflow tract was identified on non–ECG-gated CT angiogram (A and B, white arrows). Note
significant motion artifact, which limits characterization of the pseudoaneurysm. The pseudoaneurysm was subsequently repaired with a
patch with thrombosis of the pseudoaneurysm (C, white arrows), and the patient received a mechanical aortic valve replacement (C).
Follow-up image (D) 9 years after the images in A–C was obtained with non–ECG-gated high-pitch flash mode, demonstrating no
evidence of residual or recurrent pseudoaneurysm and absence of any motion artifact compared with the initial CT examination.
Calcification of the pulmonary homograft wall is a normal postoperative finding after the Ross procedure (E, black arrow).
FIGURE 8. A 70-year-old man with a history of severe aortic valve stenosis and ascending aortic aneurysm. Routine CT angiogram in
oblique sagittal (A) and axial (B) planes demonstrates normal postoperative appearance after a modified Bentall procedure, with a
pericardial (tissue) prosthetic aortic valve, and replacement of the ascending aorta with 2 grafts with the typical “waist” at the site of
anastomosis (A, black arrows). The coronary arteries have been reimplanted (A, white arrows).
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Latson et al
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Volume 00, Number 00, ’’ 2016
FIGURE 9. A 28-year-old female patient with a history of Marfan syndrome and prior ascending aortic aneurysm. The patient has
undergone the first stage of the elephant trunk procedure (A, B, C) comprising aortic arch debranching, with all 3 great vessels (black *)
supplied by a trifurcating bypass graft (black *, A) and a graft repair of the ascending aorta and arch (white *). She presented for open
repair of her descending thoracic aorta (second stage of the elephant trunk procedure). Note the “elephant trunk” extending into the
proximal descending aorta (black arrow), which represents graft material left dangling into the descending aorta to facilitate subsequent
descending aortic repair. It is important not to confuse this normal graft material for a dissection flap.
the perigraft space into the right atrium is expected to
eventually thrombose in the early postoperative phase.35
After the first stage of the elephant trunk procedure, a
graft in the aortic arch is seen as a thin peripheral density.
Proximal to the aortic arch graft, a tubular graft arises from
the ascending aorta and anastamoses with the 3 great vessels that have been removed from the aortic arch (aortic
debranching). The free distal dangling end of the graft in
the descending aorta can be mistaken for a dissection flap if
the observer does not have knowledge of the patient’s
surgical history or does not correctly identify the signs of
aortic debranching and grafting (Figs. 9–11). After stage 2
of the repair, a new surgical graft or endovascular stent is
seen in the region of the original flap in the distal aortic
arch and descending aorta.
Coarctation repair can result in narrowing and irregular contours that mimic recoarctation (Fig. 3). Thoracotomy rib deformities and surgical clips are clues to the
incidence of prior surgery. The regions of narrowing can be
assessed for any pressure gradient, if needed, with MRI.51
12 | www.thoracicimaging.com
In patients who have undergone left subclavian aortoplasty,
the proximal portion of the left subclavian will be absent,52
and the distal subclavian will opacify with collateral flow,
often from the vertebral artery.
Complications and Imaging Appearance: Immediate and
delayed complications can occur (Table 4). In the early
postoperative period, anastomotic leaks leading to mediastinal hematoma and hemothorax, retained foreign bodies,
and graft infection are complications common to all aortic
procedures. Chest radiography plays a major role in identifying enlargement of the mediastinum, implying hematoma or
developing infection. Foreign bodies include needles and
surgical sponges, which have curvilinear overlapping linear
metallic areas. CT is more sensitive for evaluation. Although
potentially occurring earlier, more delayed complications
typically relate to pseudoaneurysm, dissection, and rupture
for open surgical repairs and endoleak and stent migration for
endovascular therapy.
Pseudoaneurysms can compress the aortic lumen or
coronary arteries, with subsequent bleeding, fistula
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J Thorac Imaging
Volume 00, Number 00, ’’ 2016
Imaging of the Postsurgical Thoracic Aorta
FIGURE 10. Continued from Figure 9. Five days after the second-stage elephant trunk procedure, an inclusion graft in the descending
aorta is surrounded by the native aorta. Two precontrast images (A and C) demonstrate the utility of noncontrast images in differentiating normal pledgets (black arrows, A and B) from contrast extravasation or pseudoaneurysm. In addition, acute hematoma in the
excluded aneurysm sac that is high attenuation, an expected postoperative finding, is evident on the precontrast image (white arrow, C)
and is not as readily apparent as high attenuation on contrast-enhanced CT angiogram (white arrow, D). 3D volume-rendered image (E)
after completion of the elephant trunk procedure, demonstrating the aortic arch debranching (black *), and graft segments in the
ascending aorta/arch (white *) and descending aorta. Note the waists at the descending graft anastomosis sites (white arrows, E).
Continued aneurysmal dilatation of the abdominal aorta is noted in this patient with Marfan syndrome.
development, and frank rupture.53 The estimated incidence
is difficult to determine but has been reported in about
0.5% to 2.0% and even in up to 13% of thoracic aortic
surgeries.54–57 Pseudoaneurysms appear as saccular areas of
contrast outside the periphery of the aortic wall. Treatment
has traditionally been open surgical repair. With the
development of newer endovascular devices, percutaneous
repair with coils or occlusion devices is now possible.
Although current descriptions are limited to mainly individual case reports, these techniques will likely be more
commonly performed in the future53 (Fig. 13).
Perigraft low-attenuation collections were described as
the most common complication by Sundaram et al59 in a
series of patients studied over a span of 6 years after
thoracic aortic graft repair. The clinical implications of this
finding were quite varied, with some patients demonstrating
graft infection or dehiscence that required treatment. Others were asymptomatic and only observed. Infection is
suggested by contrast extravasation, and gas bubbles can
occur in the mediastinum with infection alone or in combination with esophagoaortic fistula. Aortopulmonary fistula is another rare complication.59
With inclusion grafts, perigraft flow most commonly
occurs at the graft ends and where the coronary buttons
anastomose with the graft.59 Calcifications in the perigraft
space can mimic enhancement, and precontrast images are
useful for differentiating. Perigraft flow can lead to aneurysm sac enlargement. Therefore, measurement of the
aneurysm sac diameter is important. An abnormal
enhancing perigraft space that surrounds the graft lumen
can be potentially misinterpreted as an ascending type A
aortic dissection if the interpreter is without knowledge of
the inclusion graft procedure (Fig. 5).60 Clinical history and
evaluation for any postsurgical material is therefore crucial.
Precontrast imaging aids in differentiating high-attenuation
acute hematoma from mild perigraft flow. A small number
of Cabrol shunts can remain patent and enhance when
perigraft flow persists, potentially leading to symptoms
from left to right shunt.61 They can be misinterpreted as a
small pseudoaneurysm or perigraft flow on contrast CT if
one is unaware of the surgical history (Fig. 5).
Dissections can occur in any remaining native aorta
between an aortic valve replacement and the ascending
aortic graft. Fine curvilinear densities involving the aortic
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13
J Thorac Imaging
Latson et al
Volume 00, Number 00, ’’ 2016
FIGURE 11. A 75-year-old female status post first-stage elephant trunk repair and cardiopulmonary bypass graft side arms. The patient’s
arch was debranched, with a trifurcated bypass graft (A, black *) to supply the great vessels (B and C, black *). Two oversewn side arms
in the graft are shown, one in the innominate artery (B, black arrow) and a second in the aortic arch graft (C, white arrow), which were
cannulated for cardiopulmonary bypass. These grafts are used to maintain cerebral perfusion during portions of the examination and
then oversewn by the surgeon. It is important not to mistake these cannulation sites for pseudoaneurysms. A linear density representing
a portion of the “elephant trunk” graft extends into the aneurysmal proximal descending aorta (C, black arrow).
root therefore can be further investigated with ECG-gated
methods and echocardiography. If so, the coronary arteries
should be analyzed for involvement by dissection.
Complications after coarctation repair include rupture
(Fig. 14), recoarctation, pseudoaneurysm, and aneurysm in
either or both the ascending and the descending
TABLE 5. Crawford Classification for Thoracoabdominal
Aneurysms46,47
Type/
Extent
I
Origin
III
Distal to left subclavian
artery
Distal to left subclavian
artery
6th intercostal space
IV
12th intercostal space
V
6th intercostal space
II
14 | www.thoracicimaging.com
aorta.50,62,63 In a large single-center review of 37 of 235
patients (16%) with coarctation, a majority of which were
repaired, the most common complication was ascending
aorta aneurysm in 9% of 235, whereas descending aneurysm occurred in 4%.64 Acute dissection, pseudoaneurysm,
aortobronchial fistula, and mycotic aneurysm also
resulted.64 Although rare, subclavian steal can develop in
patients who have had the proximal left subclavian artery
ligated as part of the subclavian flap aortoplasty.34 Therefore, the status of the subclavian and vertebral arteries
should be evaluated in all patients after coarctation repair.
Termination
Above celiac axis
CPB Techniques and Postoperative Imaging
Iliac arterial
bifurcation
Iliac arterial
bifurcation
Iliac arterial
bifurcation
Above renal arteries
Complications can occur from CPB, which is used for
oxygenating the blood during surgery. CPB entails central
venous cannulation of the right atrium or the vena cava.
The blood is oxygenated by the CPB machine, and blood
returns to the arterial system in various ways depending on
the surgery performed (Table 3). Understanding when CPB
is to be used aids in understanding the postoperative
appearance on imaging.
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J Thorac Imaging
Volume 00, Number 00, ’’ 2016
Imaging of the Postsurgical Thoracic Aorta
FIGURE 12. A 23-year-old male patient with an unrecognized Shone complex, consisting of a supravalvar mitral ring, parachute mitral
valve, left ventricular outflow tract obstruction, and aortic coarctation, who presented with acute chest pain. Initial portable chest
radiograph (A) demonstrated an abnormal mediastinal contour with prominence of the ascending aorta (A, black arrows). Rib notching
is also noted (A, white arrows). CT angiogram (B and C) demonstrated a type A aortic dissection (B and C, black arrow) and moderate
pericardial effusion (B, black *). The patient experienced cardiopulmonary arrest in the emergency department and was emergently
repaired with aortic valve replacement and graft repair of the ascending aorta. The coarctation was repaired at a subsequent elective
procedure (D), with resection of the coarctation segment and placement of an interposition graft (D, white arrows) and mechanical
aortic valve replacement (D, black arrow).
For routine ascending and descending aortic replacements, circulatory arrest is not usually needed. Ascending
aortic repairs entail CPB with arterial cannulation of the
arch or on occasion the innominate or axillary artery. Open
surgery on the aortic arch requires interruption of cerebral
blood flow. Hypothermic circulatory arrest provides a relatively safe period of time for repair with a bloodless field,
and CPB is usually required. More recently, cannulation of
the right axillary artery or innominate artery allows selective cerebral perfusion to be performed, through the right
common carotid and an intact Circle of Willis.65 On
imaging, clips or pledgets near the right axillary or innominate artery may relate to CPB cannulation sites.
Femoral artery cannulation for CPB can be used. For
descending aorta replacements, CPB may not be needed at
all (the so-called “clamp-and-sew” technique),66 but when
CPB is used the femoral artery is typically utilized for
arterial inflow. On occasion, when the distal arch is
involved by disease and there is no adequate place to put a
clamp proximally, circulatory arrest may be used for
descending replacements. The proximal anastomosis of the
aortic graft is completed first, and the femoral artery is then
used for CPB.
On CT, pseudoaneurysms from CPB appear as focal
outpouchings of contrast, often near clips or pledgets that
are used to seal the cannulation site (Table 4). Aortic grafts
equipped with side arms and side-arm grafts sewn into the
axillary or femoral artery for CPB can lead to misdiagnoses
of pseudoaneurysm (Fig. 11). Approximately 8 mm in diameter, the side arm of aortic grafts can be cannulated for
CPB to perfuse the upper body once the proximal anastomosis of the aortic graft is completed. Similarly, the end of
a side-arm graft can be sewn into the side of a right axillary
or femoral artery, so that the graft is directly cannulated for
CPB rather than the vessel, to minimize vascular and brachial plexus injury. At the completion of the procedure, the
side grafts are stapled or oversewn, forming pouches that
can mimic pseudoaneurysms (Fig. 11).12 These pouches
have high-attenuation walls on precontrast imaging that
can aid in differentiating them from pseudoaneurysms.
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Latson et al
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Volume 00, Number 00, ’’ 2016
FIGURE 13. A 48-year-old male patient with a complicated history of coarctation repair as a child, recurrent endocarditis approximately 6
years earlier, which resulted in multiple aortic and mitral valve surgeries, and new perivalvular leaks/pseudoaneurysms around both valves.
Multiple pseudoaneurysms arise from the aortic root (A), a smaller one along the right lateral aspect of the ascending aorta (A, black *), and a
large pseudoaneurysm posteriorly (A, white *), with connections to both the ascending aorta and the left ventricular outflow tract (A, white
arrows) so that it was initially misinterpreted as the left atrium. The pseudoaneurysms were percutaneously closed using multiple vascular
occlusion devices and embolization coils (B, black and white arrows). The proximal left main and left anterior descending coronary arteries are
adjacent to the posterior coil mass (B, black arrows). Non–ECG-gated high-pitch technique was critical for reducing motion artifact and for
accurately visualizing the complex connections between the pseudoaneurysms and aortic root. Reprinted with permission from Tretter et al.58
FIGURE 14. A 33-year-old female patient with Turner’s syndrome who had undergone aortic coarctation repair in the 1980s when 4 years of
age. Chest PA radiograph (A) demonstrates a large saccular aneurysm (white *) in the distal aortic arch, distal to a focal narrowing in the aortic
arch consistent with recoarctation (not shown). Surgical repair was planned in stages, with the first stage involving intentional occlusion of the
left subclavian artery originating from the proximal portion of the aneurysm sac with an endovascular device (B and E, white arrow). Surgical
left carotid to left axillary bypass grafting was also performed to supply the left upper extremity with blood flow. Postoperatively, an acute
hemothorax (B and D, black *) occurred, presumed to be related to a rupture of her descending aneurysm. She underwent emergent
successful TEVAR (C, D, E) with dilatation of her recoarctation and placement of 2 stent grafts with successful thrombosis of the aneurysm sac
(C and D, white *).
16 | www.thoracicimaging.com
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J Thorac Imaging
Volume 00, Number 00, ’’ 2016
Imaging of the Postsurgical Thoracic Aorta
FIGURE 15. A 68-year-old male patient with no known history of trauma presented with a slowly growing aortic arch aneurysm/
pseudoaneurysm over a span of 7 years (A and B, white arrows). Elective repair was performed with TEVAR (C and E, black *). The
aneurysm was too close to the origin of the left subclavian artery, and a stent graft was placed proximal to and covering the origin of the
left subclavian artery. Instead of a carotid-subclavian bypass, a “chimney” (or “snorkel”) stent was used to maintain flow into the left
subclavian artery (C–E, black arrow). 3D volume-rendered image demonstrates the chimney stent in the proximal left subclavian artery
(F, white arrow).
Endovascular Repair
Transcatheter Techniques Including Descending Aortic
Aneurysm and Coarctation Repair
Thoracic endovascular aortic repair (TEVAR) is now
the preferred technique for descending aortic repair and can
also be used for the aortic arch. TEVAR is used primarily
to treat aneurysm and traumatic pseudoaneurysms. The
United States Food and Drug Administration has
approved a variety of stent grafts that differ in terms of
TABLE 6. Aortic Zones Used for Endovascular Repair67,69
Zone
0
1
2
3
4
Description
Ascending aorta up to distal end of the origin of the
innominate artery
Zone 0 termination to the distal end of origin of left
common carotid origin
Zone 1 termination to the distal end of origin of the left
subclavian artery
Zone 2 termination to descending aorta <2 cm from the
distal aspect of the left subclavian artery origin
Descending aorta >2 cm from the distal aspect of the left
subclavian artery origin to distal descending aorta
material (Nitinol, stainless steel, polytetrafluoro-ethylene,
polyester), required landing zone lengths and diameters,
and sheath sizes used for stent delivery.67 Complex fenestrated and branched devices can now be custom manufactured for individual patients for use in the ascending aorta
and arch.68
In TEVAR, a stent graft is advanced retrograde from
the femoral vessels to the aneurysm sac and placed so that
the stent ends form a tight seal with the aortic wall at the
landing zones. Isolating the aneurysm sac from the high
pressures in the aortic lumen prevents further sac enlargement. The thoracic aorta can be divided into zones, which
facilitates accurate evaluation of endovascular therapy
outcomes (Table 6).67,69 Intentional coverage of the left
subclavian artery can be performed if the proximal aspect
of the stent cannot be landed in zone 4, which is 2 cm or
more distal to the left subclavian artery.17 The left subclavian artery supplies blood flow to the left upper
extremity, brain (through the left vertebral artery), and
spinal cord (through the vertebral, internal thoracic, subscapular, and lateral thoracic arteries). Therefore, coverage
of the left subclavian artery origin can result in blood flow
from the right vertebral artery, through the posterior circulation of the brain and left vertebral artery, to the left
subclavian artery. A left-dominant vertebral artery, any
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Latson et al
J Thorac Imaging
Volume 00, Number 00, ’’ 2016
FIGURE 16. Normal appearance of Edwards Sapien TAVR on chest radiograph (A) and noncontrast CT (B). Normal appearance of
Medtronic CoreValve on chest radiograph (C) and ECG-gated CTA (D).
absent, atretic, or occluded right vertebral artery, or
incomplete posterior circulation can lead to spinal cord
ischemia and/or cerebral symptoms (steal phenomenon).
Therefore, procedures also address (1) maintenance of
blood flow to the upper extremity and spinal cord by performing a carotid to left subclavian artery bypass graft, as
suggested by the Society for Vascular Surgery guidelines70
and (2) prevention of retrograde blood flow from the left
subclavian artery into the aortic arch around the endovascular stent (a form of type II endoleak) by ligating or
intentional thrombosing the left subclavian artery proximal
to the left vertebral artery origin (Fig. 14).
Fenestrated endovascular grafts and other percutaneous techniques are alternate methods used to maintain
subclavian artery flow. A number of techniques including
the chimney, snorkel, and periscope techniques are possible,
in which a stent graft is placed into the left subclavian
artery while placing a TEVAR graft (Fig. 15). These have
been shown to be safe and effective.71,72
A full description of aortic valve replacement options
is beyond the scope of this manuscript. However, transcatheter aortic valve replacement (TAVR), also know as
transcatheter aortic valve implantation, or TAVI, is a
catheter-based intervention that uses similar techniques as
endovascular aortic repair. TAVR is a therapeutic option
for inoperable or too high-risk patients with severe
symptomatic aortic valve stenosis.73 Often performed
transfemorally, TAVR positions an appropriately sized
18 | www.thoracicimaging.com
stent/prosthetic valve complex at the aortic valve. TAVR
can also be performed using transsubclavian, transaortic
(through an anterior right mini-thoracotomy or partial
mini-sternotomy), and transapical (through the apex of the
left ventricle) approaches.73,74
Although open surgery is still the preferred technique for
correcting coarctations in small and growing children, endovascular repair is now a safe and effective alternative in older
children and adults. Balloon angioplasty alone has been used
but is complicated by high rates of aortic wall injury and
recoarctation. Both bare metal and covered stents have been
used successfully,75 but in the Unites States, as of yet, no
balloon expandable covered stents for coarctation repair are
Food and Drug Administration approved.76
Imaging Implications and Complications
Postoperative Appearance: The chest radiograph, often
obtained in the early postoperative period, displays the
location and contour of endovascular stents. The number
of aortic stents can be evaluated, although multiple overlapping units often limit assessment. Any change in the
mediastinal contours can result from hematoma related to
aortic rupture or mediastinal infection.
After endovascular aortic repair, the stent is located
within the aneurysm sac on CT. As with the surgical
inclusion graft, the space intervening after successful repair
comprises the hematoma. The hematoma is high attenuation in the acute phase when the blood around the stent
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J Thorac Imaging
Volume 00, Number 00, ’’ 2016
Imaging of the Postsurgical Thoracic Aorta
FIGURE 17. Examples of endoleaks types I to III. A, An 87-year-old male patient with contrast extending outside the proximal portion of
the endovascular stent graft (white arrow), consistent with a type Ia endoleak. B, A 57-year-old male patient with a contrast collection
within the excluded portion of the aneurysm sac (black *), supplied by retrograde flow in a small intercostal artery (white arrow),
consistent with a type II endoleak. C, A 67-year-old male patient with contrast extending between the struts of the stent graft in the
descending aorta (white arrows), consistent with a type III endoleak.
clots and then becomes soft tissue attenuation in the
chronic phase. Volume-rendered images display the number
of stents and areas of overlap better than multiplanar
reformats. The stent struts should not extend beyond the
aortic lumen contour. Evaluation for aortic branch vessel
patency and any bypass grafts is needed. Contrast
enhancement of the left vertebral and subclavian arteries is
important to assess when the left subclavian artery origin
has been covered. Intentional occlusion of the left subclavian artery appears as low-attenuation thrombus or
metallic occlusion coils near the vessel’s origin. After
TAVR, the prosthetic aortic valve can be seen on radiographs as a metallic mesh in the region of the aortic valve,
appearing similar to a metallic stent graft (Fig. 16).
Complications and Imaging Appearance: Immediate
complications include aortic injury, dissection, and rupture
(Table 4). Peripheral vessels used for placing the stent can
have similar complications. A very rare complication,
detachment of an aortic dissection flap with distal vessel
occlusion can occur during the procedure or early postoperative period, leading to an intraluminal defect and
distal vessel obstruction on CT.77
After stent graft placement, assessment for endoleak is
mandatory. Endoleak refers to contrast within the excluded
aneurysm sac, external to the endovascular stent.17 Endoleak can lead to progressive aneurysm enlargement (Table 4
and Fig. 17). In the thoracic aorta, type I endoleaks occur
at the proximal (type 1a) and distal (type 1b) stent ends. A
tight seal at the proximal stent end is more difficult to
achieve in the thoracic aorta, given the curvature of the
proximal descending aorta and artic arch.17 Type II endoleaks, which are vessel inflow leaks, are often better seen on
delayed images and derive from intercostal arteries or
backflow from the left subclavian artery. Contrast from
feeding vessels can be seen in the periphery of the thrombus
in the excluded aneurysm sac. Type III endoleaks relate to
holes or fractures in the middle of the graft or junctional
leaks where the stents overlap, with contrast collections
near the outer stent wall. Calcifications within thrombus in
an aneurysm sac can mimic an endoleak on postcontrast
images, and precontrast imaging can help differentiate.17
Although infrequent, other potential complications
after TEVAR include stent graft kinking, stent graft
migration, and dissection.78 Graft kinking can be
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19
J Thorac Imaging
Latson et al
potentially seen on chest radiograph as a change in contour
of the stent, and migration can be detected by comparing
serial imaging. Kinking occurs particularly in areas of
aortic tortuosity, predisposing to focal luminal narrowing,
stent breakage, and type III endoleak.17,67 3D volumerendered CT images help identify kinking and aortic morphology.17 As the aorta naturally enlarges and elongates
with age, stent graft migration can occur and lead to branch
vessel occlusion. Measuring the distance between the
endovascular stent and a fixed reference point such as the
left subclavian artery origin aids in detecting migration on
radiography and CT reformats.79 After endovascular
treatment of coarctation, recoarctation, dissection, and
rupture can occur52,80 (Fig. 14).
Complications after TAVR include paravalvar leak,
which is a gap created when the walls of the valve fail to
closely approximate the aortic annulus, resulting in aortic
regurgitation.73 Other complications are coronary ostia
obstruction from displaced native aortic valvular calcifications, interference of the anterior mitral leaflet by the aortic
valve stent, and prosthetic valve leaflet thrombosis.81,82
ECG-gated CTA is an ideal method for postprocedural
assessment of TAVR valves, as MRI and echocardiography
can be limited by metallic artifact.81
CONCLUSIONS
Open surgical, endovascular, and hybrid approaches
to thoracic aortic surgery are increasingly complex. Imaging has an essential role in the postoperative evaluation of
the thoracic aorta. Protocols and image evaluation can be
tailored to the clinical question using a variety of CTA and
MRA imaging methods. Knowledge of the original
underlying disease and the repair techniques in use are
essential for accurate postoperative imaging interpretation.
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J Thorac Imaging
Volume 00, Number 00, ’’ 2016
Imaging of the Postsurgical Thoracic Aorta
SA-CME EXAM
“Imaging of the Postsurgical Thoracic Aorta: A State-of-the-Art Review”
INSTRUCTIONS FOR OBTAINING AMA PRA CATEGORY 1 CREDITSTM
The Journal of Thoracic Imaging includes CME-certified content that is designed to meet the educational needs of its readers.
This article is certified for 1.5 AMA PRA Category 1 CreditsTM and this module fulfills the requirements of the American
Board of Radiology Maintenance of Certification program for 1.5 Self-Assessment CME credits in the Radiology clinical
category. This activity is available for credit through 8/24/2017.
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SA-CME EXAMINATION QUESTIONS
Question 1
Ascending aortic aneurysm repair is now most commonly performed using:
a)
b)
c)
d)
TAVR
Inclusion graft technique
Interposition graft technique
TEVAR
Please see the following references for further study:
1. Maddalo S, Beller J, DeAnda A. A Bentall is not a Bentall is not a Bentall: The evolution of aortic root surgery. Aorta
2014;2(5):169–78.
2. Kourliouros A, Soni M, Rasoli S, Grapsa J, Nihoyannopoulos P, O’Regan D, et al. Evolution and current applications of
the cabrol procedure and its modifications. Ann Thorac Surg 2011;91(5):1636–41.
Question 2
Side arm cannulation grafts, which are used to provide perfusion of oxygenated blood during cardiopulmonary bypass, are
often oversewn at the completion of the procedure and can mimic what finding on CT angiography?
a)
b)
c)
d)
Pseudoaneurysm
Endoleak
Dissection
Intramural hematoma
Please see the following references for further study:
1. El-Sherief AH, Wu CC, Schoenhagen P, Little BP, Cheng A, Abbara S, et al. Basics of cardiopulmonary bypass: normal
and abnormal postoperative CT appearances. RadioGraphics 2013;33(1):63–72.
Question 3
Aortic debranching entails reimplantation of which vessel(s)?
a)
b)
c)
d)
Left common carotid artery
Left subclavian artery
Right innominate artery
All three great vessels
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This paper can be cited using the date of access and the unique DOI number which can be found in the footnotes.
23
Latson et al
J Thorac Imaging
Volume 00, Number 00, ’’ 2016
Please see the following references for further study:
1. Godoy M, Cayne N, Ko J. Endovascular repair of the thoracic aorta: preoperative and postoperative evaluation with
multidetector computed tomography. J Thorac Imaging 2011;26(1):63–73.
2. Castrovinci S, Murana G, de Maat GE, Smith T, Schepens MAAM, Heijmen RH, et al. The classic elephant trunk
technique for staged thoracic and thoracoabdominal aortic repair: Long-term results. J Thorac Cardiovasc Surg
2015;149(2):416–22.
3. Prescott-Focht JA, Martinez-Jimenez S, Hurwitz LM, Hoang JK, Christensen JD, Ghoshhajra BB, et al. Ascending
thoracic aorta: postoperative imaging evaluation. RadioGraphics 2013;33(1):73–85.
Question 4
The elephant trunk procedure results in a finding that can be misdiagnosed as a(n):
a)
b)
c)
d)
Aortic dissection
Intramural hematoma
Pseudoaneurysm
Stricture
Please see the following references for further study:
1. Castrovinci S, Murana G, de Maat GE, Smith T, Schepens MAAM, Heijmen RH, et al. The classic elephant trunk
technique for staged thoracic and thoracoabdominal aortic repair: Long-term results. J Thorac Cardiovasc Surg
2015;149(2):416–22.
2. Preventza O, Al-Najjar R, Lemaire SA, Weldon S, Coselli JS. Total arch replacement with frozen elephant trunk technique.
Ann Cardiothorac Surg 2013;2(5):649–52.
Question 5
The Ross procedure entails:
a) Replacing the aortic valve with the patient’s native pulmonary valve, which is replaced with a homograft.
b) Replacing the ascending aorta with a composite interposition graft.
c) Valve sparing surgery.
d) Shunt between aneurysm sac and the right atrium.
Please see the following references for further study:
1. El-Hamamsy I, Poirier NC. What is the role of the Ross procedure in today’s armamentarium? Can J Cardiol
2013;29(12):1569–76.
2. Nishimura R a., Otto CM, Bonow RO, Carabello B a., Erwin JP, Guyton R a., et al. 2014 AHA/ACC guideline for the
management of patients with valvular heart disease. J Thorac Cardiovasc Surg 2014;148(1):e1–132.
3. De Paulis R, Bassano C, Bertoldo F, Chiariello L. Aortic valve-sparing operations and aortic root replacement. J
Cardiovasc Med 2007;8:97–101.
Question 6
Delayed CT imaging aids in the detection of which type of endoleak?
a)
b)
c)
d)
I
II
III
IV
Please see the following references for further study:
1. Godoy MCB, Cayne NS, Ko JP. Endovascular repair of the thoracic aorta: preoperative and postoperative evaluation
with multidetector computed tomography. J Thorac Imaging 2011;26(1):63–73.
Question 7
What is the smallest amount of distance needed for the proximal landing zone when descending aortic endovascular repair
without arch coverage is considered?
a)
b)
c)
d)
1 cm
2 cm
3 cm
4 cm
Please see the following references for further study:
1. Godoy MCB, Cayne NS, Ko JP. Endovascular repair of the thoracic aorta: preoperative and postoperative evaluation
with multidetector computed tomography. J Thorac Imaging 2011;26(1):63–73.
24 | www.thoracicimaging.com
Copyright r 2016 Wolters Kluwer Health, Inc. All rights reserved.
Copyright r 2016 Wolters Kluwer Health, Inc. Unauthorized reproduction of this article is prohibited.
This paper can be cited using the date of access and the unique DOI number which can be found in the footnotes.
J Thorac Imaging
Volume 00, Number 00, ’’ 2016
Imaging of the Postsurgical Thoracic Aorta
2. Criado FJ, Abul-Khoudoud OR, Domer GS, McKendrick C, Zuzga M, Clark NS, et al. Endovascular repair of the
thoracic aorta: lessons learned. Ann Thorac Surg 2005;80(3):857–63.
Question 8
Which of the below criteria make asymptomatic ascending aortic aneurysms that are 4 to 5 cm eligible for repair?
a)
b)
c)
d)
Growth rate 1 mm/year
Growth rate 2 mm/year
Marfan syndrome
Chronic aortic dissection
Please see the following references for further study:
1. Hiratzka LF, Bakris GL, Beckman J, Bersin RM, Carr VF, Casey DE, et al. 2010 ACCF/AHA/AATS/ACR/ASA/SCA/
SCAI/SIR/STS/SVM Guidelines for the Diagnosis and Management of Patients With Thoracic Aortic Disease:
Executive Summary. J Am Coll Cardiol 2010;55(14):1509–44.
Copyright r 2016 Wolters Kluwer Health, Inc. All rights reserved.
www.thoracicimaging.com |
Copyright r 2016 Wolters Kluwer Health, Inc. Unauthorized reproduction of this article is prohibited.
This paper can be cited using the date of access and the unique DOI number which can be found in the footnotes.
25