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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_3823_Библиотеки_им_академика_М_И_Перельмана
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Arm Ischemia Symptoms
Arm ischemia is a rare but preventable/treatable
sequelae that can arise in about 18% of patients
undergoing subclavian coverage without preoperative
revasculation [5]. It is highly recommended for elective
cases where it is known that the patient will require
coverage of the subclavian that a carotid subclavian
bypass or a carotid subclavian transposition be
performed prior to stent‐graft placement. Decision of
carotid subclavian bypass versus transposition is highly
based on prior coronary artery bypass. Using a LIMA
conduit as a transposition will compromise flow to the
LIMA bypass during the procedure and can cause a
myocardial infarction.
The Society for Vascular Surgery (SVS) has laid out
specific guidelines with regard to coverage of the
subclavian artery which are easily accessible on the SVS
guidelines smartphone application. In emergent cases,
the subclavian should be covered if needed so as to avoid
type 1a endoleaks and careful postoperative monitoring
of arm ischemia symptoms must occur. If the patient
develops significant ischemic symptoms of the hand after
coverage of the subclavian, revascularization should be
performed. In patients who need elective TEVAR where
coverage of the subclavian will be needed for appropriate
seal, a preoperative subclavian revascularization is
suggested.
CTA Surveillance/Endoleak Types
There is no general consensus for exact timing of CTA in
the postoperative period or long‐term surveillance.
Therefore, it is up to physicians to have their own
standard for timing of CTA. Many providers obtain CT
scans at 1 month, 2 months, 6 months, 12 months, and
yearly thereafter to look for aneurysmal degeneration
and/or endoleak formation [6]. Some providers obtain
CTA prior to discharge in higher risk patients especially
in those who presented with acute dissection, trauma, or
rupture. Endoleak formation can be a very detrimental
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factor in the perioperative period and during
postoperative surveillance.
There are five distinct endoleak types (Figure 4.12):
1. Type 1: leakage between the graft and aortic wall
either at the proximal seal zone (1a) or the distal seal
zone (1b)
2. Type 2: back‐bleeding from another vessel
(subclavian, intercostals)
3. Type 3: inadequate overlap between two stents
Figure 4.12 Endoleak classification.
4. Type 4: increased porosity of the stent‐graft
5. Type 5: endotension; increased size of aneurysm sac
without other known source.
Types 1 and 3 when seen in the operating room should be
repaired as they are technical failures. Type 2 endoleaks
if small may be watched as they may revert on their own.
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References
1 Faiza, Z. and Sharman, T. (2022). Thoracic Aorta
Aneurysm. Treasure Island (FL): StatPearls
Publishing.
2 Hiratzka, L.F., Bakris, G.L., Beckman, J.A. et al.
(2010). 2010
ACCF/AHA/AATS/ACR/ASA/SCA/SCAI/SIR/STS/S
VM guidelines for the diagnosis and management of
patients with Thoracic Aortic Disease: A report of the
American College of Cardiology. Circulation 121 (13):
e266–e369.
3 Cambria, R.P., Brewster, D.C., Gertler, J. et al. (1988).
Vascular complications associated with spontaneous
aortic dissection. J. Vasc. Surg. 7 (2): 199–209.
4 Cambria, R.P., Conrad, M.F., Matsumoto, A.H. et al.
(2015). Multicenter clinical trial of the conformable
stent graft for the treatment of acute, complicated
type B dissection. J. Vasc. Surg. 62 (2): 271–278.
5 Woo, E.Y., Carpenter, J.P., and Jackson, B.M. (2008).
Left subclavian artery coverage during thoracic
endovascular aortic repair: A single‐center
experience. J. Vasc. Surg. 48 (3): 555–560.
6 Upchurch, G.R. Jr., Escobar, G.A., Azizzadeh, A. et al.
(2021). Society for Vascular Surgery clinical practice
guidelines of thoracic endovascular aortic repair for
descending thoracic aortic aneurysms. J. Vasc. Surg.
73 (1): 55S–83S.
5
Endovascular Abdominal Aortic
Aneurysm Repair (EVAR)
John Futchko, Katie MacCallum, and Aksim G.
Rivera
Department of Surgery (Vascular Surgery), Albert
Einstein College of Medicine-Jacobi Medical Center,
Bronx, NY, USA
Introduction
Since it was first described in 1986 [1], endovascular
aneurysm repair (EVAR) has become the preferred
treatment option for many patients with abdominal
aortic aneurysms (AAAs). Multiple studies have shown
lower 30‐day mortality rates and fewer perioperative
complications as compared to open AAA repair [2–4].
Initial concerns regarding durability largely have been
alleviated by stent‐graft redesign and follow‐up trials
examining long‐term outcomes [5–7]. While overall
complication rates are favorable, reintervention rates
remain significantly higher than open repair [8].
EVAR requires extensive preoperative planning
including appropriate patient selection, detailed
imaging, measurements, and graft selection. There are
various intraoperative pitfalls, such as vascular access
and endoleaks, which the surgeon must be able to
identify and troubleshoot. This chapter will provide an
overview of the steps of the procedure as well as
management of potential issues that may arise.
Patient Selection
Though EVAR is appropriate for most patients, including
those otherwise deemed too high‐risk for open repair [9],
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it is not “one size fits all.” Various criteria should be
considered, particularly anatomic suitability.
One advantage of EVAR over open repair is that it may
be performed under anesthesia suited to the patient’s
needs. General anesthesia is commonly used; however,
either regional (spinal or epidural) or local anesthetic
with sedation may be chosen depending on the
individual’s comorbidities and type of access to be
performed. This gives the anesthesiologist relative
flexibility as compared to open repair which mandates
general anesthesia.
Potential anatomic challenges include a short or severely
angled aortic neck, circumferential thrombus, and iliac
artery disease, but none of these alone is an absolute
contraindication [10–12], particularly with
advancements in graft design. Most surgeons consider
the character of the neck to be the most important
anatomic factor with length, diameter, angulation, and
shape all playing important roles in the seal of the
proximal graft. Pitfalls related to poor distal vessel
quality will be addressed later in the section on vascular
access. Preoperative imaging is essential to identifying
these issues.
Preoperative Imaging and
Measurements
All patients undergoing EVAR will require preoperative
imaging. Computed tomography arteriography (CTA)
with three‐dimensional (3D) reconstructions is the most
common and the most useful for planning. Multiple
software packages are available, including open source
platforms, which enable the surgeon to create precise
measurements accounting for the angulation and
rotation of the blood vessels involved through centerline
reconstructions (Figure 5.1).
Figure 5.1 Pictured on the left is a traditional CTA
coronal view of an infrarenal aneurysm. To the right is
3D reconstruction using available software. Such
imaging modalities allow for accurate sizing and pre‐
operative case planning.
As proper CTA requires intravenous contrast
administration, it should be performed judiciously in
those patients with chronic kidney disease or concern for
contrast allergy. For those who are unable to receive
contrast dye, noncontrast may be performed.
Unfortunately, this will lead to a subpar understanding
of the patient’s anatomy. Distal occlusive disease or the
presence of laminated thrombus may not be appreciated.
In these patients, alternative imaging may also be
considered such as carbon dioxide angiography [13] or
intravascular ultrasound (IVUS). IVUS has also emerged
as an essential intraoperative adjunct in performing
EVAR for all patients [14].
Graft Selection
Once the surgeon has decided EVAR is a suitable option
for an individual patient, the next crucial step is selection
of the stent‐graft itself. There are multiple companies
with devices currently approved for use in the United
States and even more in clinical trials. In choosing a
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graft, one must consider the following key components:
profile, graft material, stent material, modularity, ease of
use, and range of treatable aortic neck and iliac artery.
The delivery system profile is of particular importance in
an aging population or in female patients who may have
smaller femoral vessels, thus limiting access. At the time
of writing, the smallest delivery sheath system is the
Alto™ system (Endologix, Irvine, CA, USA) with an
outside diameter (OD) of 15 Fr. All commercially
available grafts are currently made with either woven
polyester or polytetrafluroethylene (PTFE), similar to
materials used during open surgical repair. Proximal
fixation may be either infrarenal or suprarenal
depending on the inclusion of a bare‐metal stent
component. Positive fixation may be achieved with
additional features such as metal hooks, barbs, anchors,
or staples. Additional graft features, such as column
support and radial force, will assist with fixation and,
ideally, prevent caudal migration over the life of the
device.
Manufacturers have selected to produce either bi‐ or tri‐
modular devices, with three‐piece grafts consisting of the
main body and individual iliac limbs as opposed to a
main body and iliac piece with a separate contralateral
limb piece. Graft selection depends not only on patient
anatomy but also on the operator’s comfort with the
system.
Graft Sizing
Each stent‐graft has unique features and thus requires
specifically tailored measurements. Most manufacturers
have worksheets available to assist in sizing. Generally
speaking, grafts should be oversized approximately 10–
20% in comparison to the diameter of the aortic neck
and iliac arteries to minimize the risk of graft
complications, including graft migration and both early
and late endoleak during aortic remodeling. While each
available endograft device has its own specific
instructions for use (IFU), there are several general
guidelines in sizing, which can help to determine the
complexity of repair required dependent on individual
patient anatomy.
Neck Length
One of the most crucial initial measurements in
endograft sizing is the distance between the lowest renal
artery and the most proximal portion of aneurysmal
aorta, typically referred to as the “neck length.” This
segment of aorta acts as the proximal fixation point for
the sealing stents found at the proximal ends of most
endograft devices. While there is some variation, as some
grafts, such as the Zenith™ (Cook Medical, Bloomington,
IN, USA), have bare‐metal suprarenal fixation stents,
these sealing zone stents provide the necessary wall
apposition that leads to aneurysm exclusion. Equally as
important is the quality of this aortic segment, as the
presence of even mild aneurysmal degeneration or
thrombus can lead to intraoperative embolic events,
endoleak, or improper aortic remodeling. In general, an
aortic neck of at least 15 mm is required for on‐label use
of most commercially available endografts. However,
there are two available devices, the Endurant™
(Medtronic, Minneapolis, MN, USA) graft and Alto graft,
which have specific IFU for aneurysms with less than 10
mm of available neck. In the case of the Endurant graft,
the use of endoanchors improves apposition and fixation
and allows for deployment with as little as 4 mm of
available neck length.
Neck Diameter
The measurement of the aortic neck diameter is essential
to prevent repair failure and thus equally as important in
endograft sizing as neck length. It is typically taken 15
mm from the lowest renal and involves a wall‐to‐wall
measurement in the axial cuts in a plane perpendicular
to the course of the aortic lumen; although this may vary
based on device. Most device manufacturers recommend
oversizing by 10–20% of the aortic diameter. In doing so,
current EVAR devices can accommodate aortic
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diameters between 18 and 32 mm. Oversizing assures
adequate wall apposition and reduction of the risk of a
type I endoleak. However, overzealous oversizing can
result in graft pleating of the fabric and type I endoleak,
as well as an increase in late graft migration and aortic
neck dilation. This is also important to remember in
patients with conical aortic necks. In such cases, most
recommend taking the average of both diameters to
determine a final endograft stent size.
Branch Vessels
In cases where aneurysmal degeneration extends into the
visceral segment and the patient is not suited to open
repair, there are several endovascular options falling into
three general categories: fenestrated endografts, parallel
grafts, and debranching procedures.
Fenestrated endografts have now become commercially
available (Zenith). Tailored to an individual patient’s
anatomy, these custom‐made endografts allow for
endovascular repair of juxtarenal aneurysms through
creation of windows in the endograft designed to align
with aortic branch vessels allowing for perfusion (and
possible stenting) of visceral arteries. These devices have
their own anatomic limitations and offer only limited
treatment options in “off‐the‐shelf” emergent repair
situations.
When such devices cannot be utilized, alternative
complex endovascular techniques allow for appropriate
repair and coverage. Parallel stent‐grafts, which include
snorkels, periscopes, and chimneys, refer to stent‐grafts
placed in parallel alongside aortic endografts to allow for
perfusion of branch vessels that would otherwise be
covered. These repairs are often complicated with
endoleak between stent‐grafts, so called “gutterleaks,” as
well as stent‐graft thrombosis and type I endoleaks.
Debranching refers to open surgical debranching and
bypass of visceral vessels (i.e. celiac, SMA, and renal
arteries) to alternative arterial inflow targets (typically
iliac arteries) prior to planned endograft coverage.
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