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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_3892_Библиотеки_им_академика_М_И_Перельмана
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395
What is a
periscope
graft?
A “periscope” or “reverse chimney” technique
describes the placement of the covered stent
below the distal edge of the main aortic stent
graft. This facilitates the extension of the distal
seal zone in thoracoabdominal or abdominal
aneurysms.
When used in TEVAR, it is used to preserve the
LSA (Hakim).
What are the
characteristics
of a sandwich
EVAR?
The “sandwich” technique involves the placement
of a covered stent positioned between two
aortic main body components in order to
maintain side branch perfusion in mid-graft
position. Novel approaches have been described
utilizing a combination of chimney grafts and
periscopes with and without sandwiching the
grafts with a bridging graft in the treatment of
thoracoabdominal aneurysms (TAAA).
Which are the
advantages of
using parallel
endografts?
The parallel techniques are performed using a
variety of endografts and covered or uncovered
stents that are readily available “off-the-shelf”
and employed on urgent cases. When compared
to fenestrated and branched grafts (fEVAR)
techniques, parallel techniques are usually
cheaper and can be less time-consuming.
Additionally, these techniques can be used as a
“bail out” procedure in the setting of accidental
over stenting of visceral aortic branches during
conventional EVAR.
Which are the
disadvantages
of the parallel
endografts?
The major disadvantage of EVAR via parallel
techniques (chEVAR) is the development of
gutter leaks, a form of type I endoleak caused by
blood flow into the potential space between the
aortic wall and the multiple stent grafts. Gutter
leaks can also result in kinking, compression,
and eventual occlusion of one or multiple graft
components. Hakim etal. report resolution
of most type 1a endoleaks after TEVAR on
follow-up scans.
(continued)
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How can
risk of gutter
formation be
decreased?
Techniques that improve graft-aortic wall
apposition decrease the rate of gutter formation.
These include the use of more conformable aortic
stent grafts, oversizing of the main aortic stent
graft, and avoiding multiple chimney grafts.
What
increases the
risk of gutter
formation?
Positioning the snorkeled or chimney grafts
obliquely rather than parallel to the main aortic
endograft decreases aortic wall apposition at the
seal zone, resulting in increased chance for gutter
formation.
What are
fenestrated
endografts?
Fenestrated grafts are composed of a main aortic
endograft body that extends its proximal sealing
zone above the infrarenal segment. These grafts
have fenestrations or scallops corresponding to
excluded visceral vessels in order to maintain the
visceral perfusion.
Fenestrated endovascular aortic repair (fEVAR)
maximizes the interaction between the aortic
endograft and the aortic wall while maintaining
visceral perfusion.
Planned overlap between aortic endograft and
branch stents reduces the risk of component
separation, type III endoleaks, and protrusion of
branch stents into the main stent graft.
They are currently designed specifically for
each patient using CT data, requiring time for
construction. However, off-the-shelf varieties,
which contain fenestrations and scallops to treat
the majority of patient anatomies, are currently in
development.
Fenestrated endografts can also potentially be
created by the physician on the “back table” in a
customized manner.
What are the
advantages of
fEVAR?
Fenestrated endografts have lower risk of
proximal endoleaks in juxtarenal aortic
aneurysms since they are free of gutters creating
better sealing. They present better results in
short- and long-term data when compared to
chEVARs. The specific radiopaque markers offer
guidance for optimal positioning.
O. Adenikinju et al.
https://t.me/med1917
397
What are the
disadvantages
of fEVAR?
Most limitations are associated with the length
of time needed to manufacture the customized
fenestrated devices and higher cost. They are
not available “off-the-shelf” thus they are not
available in urgent settings.
What is a
branched
endograft?
Branched endografts are composed of a main
body device with renal and visceral branches
that extend to maintain flow. Manufacturers
offer different devices with a wide variety of
attachments for the branch components. The
branched EVARs are currently Investigational
Device Exemption (IDE) in the United States,
though most of them are already approved in
Canada and Europe.
What are the
advantages
of branched
EVAR?
Branched devices also known as directional
branched devices are used mainly for treatment
of TAAAs. They present as an “off- the- shelf”
option to long-segment TAAAs (Crawford IV),
and are suitable for emergent or urgent cases.
Which are the
disadvantages
of the
branched
EVARs?
The coverage of long-segment TAAAs with
endografts is associated with higher rates of
spinal ischemia and its complications.
What is an
EVAS?
The endovascular aneurysm sealing system
(Nellix EVAS; Endologix, Irvine, CA, USA)
consists of two balloon-expandable stents which
support the aorta flow channel which expands
from the non-aneurysmal aorta proximally to the
iliac arteries distally. Surrounding the endografts,
nonporous PTFE-
based endobags are filled using
biocompatible polyethylene glycol polymer,
adjusting the endobag to fit the aneurysm sac
lumen. This allows sealing of the aneurysm and
resists displacement. At the time of authorship,
the Nellix System is an investigational device as
part of the EVAS2 study, in the United States.
(continued)
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How much
do the stent
grafts need to
be oversized?
Thoracic endograft stent is oversized 0–20%
based on the pathology (i.e., aneurysm, dissection,
trauma)
Chimney stent graft sizing is based on the type of
graft:
Self-expanding stent graft: oversized 0–20%
relative to the diameter of the branch vessel
(e.g., Gore Viabahn (W.L.Gore & Associates,
Flagstaff, AZ))
Balloon-expandable stent graft: oversized
0–5% (e.g., Atrium iCast)
Which type
of chimney
stent grafts is
preferred?
Balloon-expandable stent grafts have higher
radial force when compared to self-expanding
stents, and thus have lower rates of reported
occlusion. However, it must be kept in mind
that the type of stent used is highly operator
dependent, in the context of chEVAR, since it is
considered an off-label procedure.
What is
a Dacron
elephant
trunk graft
(ETG)?
Ascending aortic hemiarch graft with proximal
branch trifurcation anastomosis to the great
vessels (simulating takeoff from a conventional
three-vessel arch)
Frozen elephant trunk procedure is a surgical
option, which allows single-stage repair by
placing antegrade endovascular ETG in the
descending aorta under direct visualization
during hypothermia (Preventza, 2013).
What is the
advantage
of using an
ETG?
Serves as anchor for adjunct stent graft and
prevents proximal endoleak
How is
the ETG
identified
during the
second stage
endovascular
repair?
1. Four radiopaque clips at distal periphery of the
graft
2. Pacing wires hang from the distal aspect of the
graft
O. Adenikinju et al.
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Indications/Contraindications
If proximal landing
zone is<2cm with the
ascending aorta, what
approach is indicated?
Zone 0 hybrid repair with Dacron
graft placement for landing zone
What is the indication
for elephant trunk
technique?
Unable to rebuild proximal landing
zone in an aneurysmal ascending
(zone 0) and descending aorta
pathology
What is the difference
in treatment strategy
between pathology
affecting aortic zone
0 and aortic zones 1
through 3?
Pathology affecting zone 0 likely
requires a sternotomy with
debranching as it must be repaired
with either open aortic arch
replacement or a hybrid procedure
(i.e., elephant trunk followed by
TEVAR). Pathology affecting zones
1 through 3 frequently can be treated
without a sternotomy or debranching
with extra-anatomic bypasses to the
cerebral vessels with subsequent
TEVAR (Xydas etal.).
During zone 2 repair,
the left subclavian artery
is not always preserved.
What are the absolute
indications for LSA
revascularization?
Dominant left vertebral artery or
absent right VA
Patent left LIMA-LAD bypass
Left AVF/AVG for hemodialysis
What are the relative
indications for LSA
revascularization?
Prior LUE ischemia
Risk of spinal cord ischemia due to
large stent graft (thyrocervical trunk
feeds anterior spinal artery)
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General Step by Step
What are the
various arterial
access options
that can be
performed for
intervention?
Open: Vascular cutdown to the upper extremity or
femoral arteries or retroperitoneal aortic exposure
Minimally invasive:
Femoral: US-guided standard Seldinger
technique followed by percutaneous
arteriotomy closure device (i.e., ProGlide
Abbott Vascular, Redwood City, CA)
US-guided standard Seldinger technique for
brachial access
If a patient has
small-
caliber
external iliac
arteries, when
should a
retroperitoneal
exposure be
considered?
When the device requires 24–26F access sheaths
What are
the access
requirements
to perform
a parallel
grafting
technique?
The minimal vessel diameter must accommodate
on one side a conventional femoral approach
16–22F (for the main aortic device).
The contralateral femoral access minimal sheath
size is highly variable by manufacturer and
endograft type.
For the visceral vessel to be stented, an additional
access for a 6–8 Fr sheath is typically required,
targeted at the vessel of interest.
What steps
must be
considered
when planning
complex aortic
repair?
Determining if the access arteries will
accommodate large sheaths.
Prospective planning is needed to determine if
exclusive percutaneous approach will be possible
(availability of 2 femoral arteries +1 or 2 upper
extremity) or surgical conduit needed.
Use of simulators or 3D printed models is growing
in order to attempt to decrease procedural time
and complications.
Meticulous analysis of measurements and
aneurysm characteristics: proximal neck length,
diameter, mural calcification, presence of
thrombus, and angulation.
O. Adenikinju et al.
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Complex Abdominal Aortic Aneurysm (AAA)
What additional step
must be accounted for
during preoperative
AAA repair planning
after the main body is
deployed?
Plan cannulation of the contralateral
gate.
How are the abdominal
aortic endografts
deployed?
The deployment of the main body and
iliac branched endografts is specific to
each manufacturer. However, once the
snorkeled/chimney stents are in place in
the visceral vessels, balloons are inflated
at the same time in a kissing balloon
fashion to form the final configuration.
What are the steps
of a generic fEVAR
procedure?
1. Main aortic fenestrated graft (with
visceral branch pre-cannulation or
not
a
)
2.
Visceral branch covered stent
deployment
3. Distal bifurcated stent graft device
delivery
4. Iliac extension placement if needed
a
The aortic branch vessels can be pre-cannulated for alignment or
after the fenestrated device is placed for delivering the covered
stents
Complex TEVAR
Where is the
optimal position of
the chimney graft
in a TEVAR?
2cm beyond the thoracic endograft in the
ascending aorta and at least 2cm within the
target vessel
Where is the
optimal position of
the periscope graft
in a TEVAR?
Beyond 2cm of the endograft to decrease
the chance of an endoleak
(continued)
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What artery
is targeted for
the side branch
component
of a branched
endograft with a
proximal landing
in zone 2?
Left subclavian artery (LSA). If the landing
zone is in zone 0 or 1, extra-anatomical
bypass is needed to revascularize the left
common carotid artery (LCCA) and/or LSA.
What is the
advantage of
having multiple
sites of access
when deploying a
branched device?
The GORE TAG Thoracic Branch
Endoprosthesis (TBE) can be deployed
via common femoral access only. However,
Hakim etal. advocate “through-and-
through” access where an exchange wire is
placed in the brachial artery (for zone 0 or
2 repair) or LCCA (in zone 1 repair) and
snared through the CFA to help deploy the
side branch, especially when the target vessel
is angulated or tortuous.
Hybrid: Open±TEVAR
What are the steps of a zone 1
hybrid repair?
1. Carotid-carotid bypass
anastomosis to mid left
subclavian artery:
Alternative: Left carotid-
subclavian bypass and then
snorkel LCCA as the stent
excludes the vessel
2.
Occlude the left common
carotid artery and proximal
LSA.
3. Retrograde deployment of
endograft.
Why are the LSA and LCCA
ligated (or coiled) during zone 1
repair?
To prevent type 2 and type 1
endoleaks, respectively
O. Adenikinju et al.
https://t.me/med1917
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What are the steps of a zone 0
hybrid repair?
1. Left subclavian-carotid
bypass
2. Debranching of LCCA and
assess for cerebral ischemia
via EEG with clamp test
3.
Innominate artery
debranching
4. Retrograde or antegrade
deployment of endograft
How long is a typical clamp test
performed during a zone 1 hybrid
repair?
3min
When a patient with an ascending
aortic aneurysm cannot undergo
cardiopulmonary bypass,
what technique is utilized for
treatment?
Aortic wrapping with Dacron
graft (Preventza, 2013)
What are the steps of a total
thoracic aortic aneurysm repair?
1. Modified Mt. Sinai
technique: total arch
replacement + Dacron
elephant trunk
2. Snare pacing wires to
prevent intussusception
of endograft during
retrograde deployment of
endograft
Relevant Materials
What intraoperative
support/monitoring
can be used in complex
aortic hybrid repairs?
Cardiopulmonary bypass
Spinal cord motor and sensory
neurophysiologic monitoring
Transesophageal echocardiography
Electroencephalography (EEG) to
monitor for signs of ischemic infarction
during arch debranching (Zone 0
repair)
(continued)
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During hemiarch
replacement, what may
be used to maintain
cerebral perfusion?
Deep hypothermic circulatory arrest
with either selective antegrade cerebral
perfusion (SCAP) or retrograde
cerebral perfusion (Preventza, 2013)
How is perfusion
maintained with
SCAP?
An arterial cannula allows bypass flow
thru an 8 or 10mm Dacron graft that is
anastomosed to the right axillary artery
allowing antegrade cerebral flow.
How is perfusion
maintained in RCP?
Retrograde flow via bypass cannula
in the SVC with goal central venous
pressure of less than 20mmHg.
What periprocedural
support is needed if
multiple fenestrations
are planned during
TEVAR?
ECMO.During in situ fenestration
(ISF) via laser or ablation techniques,
ECMO can be avoided if single-vessel
ISF is performed promptly by an
experienced operator.
When is preoperative
lumbar drain placement
indicated (Chisea)?
Ideally, a preoperative lumbar drain is
placed in every TEVAR case, especially
in the setting of:
1. Planned coverage of parent
intercostal artery giving rise to the
Adamkiewicz artery
2. Long-segment endograft spanning
the native aorta
a
3. Early postoperative spinal cord
ischemia symptomatology
4. Previous or concomitant repair of
infrarenal aorta
5. Occlusion the internal iliac arteries
(reduced collaterals)
6. When the segment treated includes
the thoracic aortic
7. Coverage of the left subclavian
artery origin without
revascularization
8. Renal failure
a
The length of the aortic segment treated is the most significant risk
factor for the occurrence of spinal ischemia (The longer the seg-
ment, the higher the risk)
O. Adenikinju et al.
https://t.me/med1917
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