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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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Aortic Length Measurements
Calculating the aortic length to repair requires several
measurements: the lowest renal artery to the aortic
bifurcation, the bifurcation to the right hypogastric
artery, and the bifurcation to the left hypogastric artery.
These measurements can prove challenging, especially in
the case of a tortuous aorta or iliac arteries; however, this
can be aided with the use of centerline reconstruction
software.
For most devices appropriate wall apposition requires at
least 10 mm of distance between the aortic bifurcation
and the internal iliac artery. The need for longer iliac
limbs typically occurs in patients with more tortuous
iliacs. Patients with splayed aortic bifurcations may
benefit from “balleting” (crossing) the iliac limbs, which
also requires longer limb lengths (Figure 5.2).
The distal seal zone along the iliac vessels also plays a
critical role in graft sizing. As with proximal fixation,
distal fixation typically requires 10–20% oversizing of
the measured iliac diameter and is crucial to prevent
type IB endoleaks, iliac aneurysmal degeneration, or iliac
thrombosis. Iliac arteries less than 7 mm or greater than
25 mm may render endovascular treatment unsuitable.
For patients with concurrent iliac occlusive disease,
treatment of such lesions should occur prior to endograft
placement, as these aortic endografts do not provide the
radial force necessary for treatment of stenotic lesions.
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Figure 5.2 In cases where aortic anatomy is not suitable
for on‐label device use, graft alteration or “physician‐
modified endografts” as pictured above can provide an
endovascular solution in patients who are otherwise poor
candidates for difficult open repairs.
For patients with concurrent aneurysmal iliac disease,
the Iliac Branch Excluder™ Device (W.L. Gore, Flagstaff,
AZ, USA) allows for canalization and preservation of the
iliac branch vessels, with exclusion of associated
aneurysm. These devices are especially important in
patients with occluded contralateral hypogastric vessels.
Step 1. Vascular Access
Percutaneous
Ultrasound‐guided percutaneous access has become
increasingly routine in both EVAR and thoracic
endovascular aortic repair (TEVAR) over the past
decade. Multiple peer‐reviewed studies have
demonstrated that percutaneous access offers patients
shorter procedure times and length of stay, as well as
decreased postoperative pain and access site wound
complications [15, 16]. Percutaneous access can be safely
achieved with sheaths up to 24 Fr, which accommodate
most commercially available devices. Safe closure of the
percutaneous access can be achieved with any of the
large‐access closure devices available in the market.
As in device sizing and selection, the use of percutaneous
access is dependent on patient selection. Those patients
with scarred or hostile groins (i.e. previous surgery,
radiation, or cancer) tend to benefit from open exposure.
Vascular anatomy also plays a key role in decision‐
making. Patients with a high femoral bifurcation or
significant calcific or occlusive iliofemoral disease may
not be amenable to percutaneous access. Likewise,
patients with small iliofemoral vessels, typically women,
usually have limited options for delivery systems. While
sometimes overlooked, one ought to remember that
vascular access is one of the most crucial portions of the
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EVAR procedure, the one from which most
complications arise. Due to the inherent risks, the ability
to convert to open for access and surgical closure must
be available.
Initial access is similar to that of a standard lower
extremity angiogram and should be performed under
ultrasound guidance to limit the risk of complications.
The optimal access target is along the anterior surface of
the common femoral artery between the inguinal
ligament and femoral bifurcation. Arterial cannulation
can be obtained using either a standard “single‐wall” 18‐
gauge needle or with a “micropuncture” 21‐gauge needle,
with wire choice dependent on operator preference and
anatomic profile. Access location relative to the femoral
head and subsequent placement of guidewire into the
iliac system is then confirmed under fluoroscopic
imaging.
Open
With the advent and widespread adoption of
percutaneous access devices, open access has become
less common; however, still has its place in specific
patient populations. As mentioned above, open exposure
plays an important role to avoid potentially devasting
access complications. When performed, a vertical or
oblique incision can be utilized. While a vertical incision
allows for additional exposure of the femoral vessels,
oblique incisions tend to be favored by operators due to
decreased rates of wound complications [17].
Iliac Disease and Conduits
Even after successful groin access, iliac occlusive disease
may be a major hindrance to endograft deployment.
Evaluation of the iliac vessels on preoperative CTA
allows for planning sheath navigation and device
approach through potentially diseased and tortuous
vessels. Wire selection and access during this portion of
the procedure is crucial. Any placement of dilator
sheaths and larger devices should occur over very stiff
wires. Wire selection will be discussed in detail later in
the chapter. Additionally, it is crucial to maintain wire
placement across the iliac arteries throughout the
duration of the case. In many instances, the damage in
diseased iliacs occurs with vessel injury or disruption
upon removal of a large bore sheath. In these devastating
moments, a stiff wire can provide life‐saving access.
There are several approaches to iliac occlusive disease,
dependent on the degree of disease and device used.
Often, focal iliac lesions can be treated prior to sheath
insertion with balloon angioplasty. For patients with
more significant disease that requires stenting, there are
two key concepts to remember. First, these aortic
endografts do not provide the radial force to maintain
long‐term patency in the iliacs, and thus should not be
used in lieu of a stent. Second, if stenting is required, it
should be done following deployment of the endograft,
given the tendency for many bare‐metal stents to migrate
with repeated manipulation.
There are several endovascular techniques that allow for
access in the case of small or diseased iliac arteries. One
option is to create an “internal endovascular conduit” by
placing oversized, covered stents in the common and
external iliac arteries and balloon‐expanding them to a
sufficient diameter. Another is the use of a recently
developed balloon‐expandable sheath (SoloPath, Onset
Medical Corp, Irvine, CA, USA). The sheath, which
contains an incorporated angioplasty balloon, is initially
inserted with a size of 14 Fr then expanded to size 24 Fr,
enough to accommodate most devices.
In select cases, the use of a surgically placed graft
conduit can be performed to completely bypass diseased
and calcified iliac and femoral vessels. The conduit
should be performed through a right or left oblique
retroperitoneal incision. Taking extreme care to stay
retroperitoneal, it is possible to expose an adequate
segment of common iliac artery to allow for graft
anastomosis. An end‐to‐side anastomosis in the distal
common iliac artery with 10 mm prosthetic conduit. The
conduit is then tunneled under the inguinal ligament
into a femoral counter incision to be used appropriately
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for the remainder of the procedure. At the completion of
the EVAR, the conduit may be either ligated, a small
segment left for later access, or anastomosed to the
common femoral artery.
Step 2. Imaging
Equipment
Successful access and appropriate device selection mean
little without quality fluoroscopy equipment. Many
institutions today have at least one “hybrid” room, which
combines a contemporary fixed‐imaging unit with
traditional operating room capabilities. The procedure
may also be performed with the traditional “C‐arm”
fluoroscopy unit. In both situations, the operator must
be comfortably using the equipment efficiently and
safely.
Neck Angulation
Many infrarenal aneurysmal necks have varying degrees
of angulation, often in an anterior orientation. In order
to appropriately correct for this and to remove any
parallax in the imaging, a degree of adjustment in the
fluoroscopy unit is typically required. This can be
calculated using the preoperative CTA in a centerline
software system and involves creating an angle
perpendicular to the neck of the aneurysm.
Renal Arteries
In a similar fashion, the left renal artery typically
originates slightly posterior and lateral on the aorta,
requiring adjusting the gantry angle with some degree of
left anterior oblique (LAO) to allow for adequate
imaging. For patients with accessory renal arteries and
normal renal function, these can typically be covered
with the endograft without the need for embolization.
Step 3. Wires
With bilateral femoral access established, wire access
across the diseased aorta must be achieved. This can
initially be done with a soft‐tipped wire (e.g. Glidewire,
Terumo, Sunrise, FL, USA) under fluoroscopic imaging.
This wire should be exchanged over a soft catheter for a
stiff guidewire (e.g. Lunderquist and Amplatz), which
should be placed in the distal thoracic aorta. One must
ensure that these wires are not withdrawn or advanced
during the procedure. Repositioning of a stiff guidewire
without fluoroscopic guidance can result inadvertent
cannulation of an arch vessel or aortic valve, aortic
plaque or thrombus disruption, or aortic dissection.
Once stiff wire access is established via one femoral
sheath, a pigtail catheter with radiopaque markers can
be advanced over a soft wire in the contralateral sheath.
If there is question about possible iliac occlusive disease
that requires preprocedure treatment, or if there is
concern regarding aneurysmal anatomy (aortic length,
renal artery location), angiography and intervention can
be performed at this time.
Step 4. Delivery and Deployment
Main Body
Graft Orientation
Prior to insertion, the contralateral gate should be
oriented under fluoroscopy. Typically, this involves
maintaining orientation based on fluoroscopic graft
markers to ensure the gate opens aligned with the
contralateral common iliac to facilitate cannulation. The
decision to cross the graft limbs is an exception to this
orientation. This decision is sometimes guided on initial
wire access with splayed bifurcations. If the wires appear
to sit crossed low in the aneurysm, the operator should
consider crossing the limbs in order to limit endotension,
especially in shorter body devices such as the Gore
Excluder. For longer body devices like the Cook Zenith,
which have the contralateral gate closer to the
bifurcation, such a maneuver is less optimal.
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With orientation confirmed the device should be
advanced slowly under fluoroscopy to confirm that
positioning is maintained. Any rotation to the graft
should be performed while the graft is being advanced to
avoid building up unnecessary torque in the device. Care
should also be taken to avoid rotating the graft within the
proximal neck due to risk of embolic events from aortic
thrombus. If there is a large thrombus burden, consider
systemic heparinization prior to graft or wire insertion.
If insertion of the endograft device proves difficult, due
to tortuous iliacs or distal aorta, there are several
troubleshooting options available. The contralateral wire
can be exchanged to a stiffer wire to take out any residual
tension in the aneurysm or aortic bifurcation. A “buddy
wire” of a second stiff wire can also be advanced up the
ipsilateral system, to further straighten any tortuous
segment.
Proximal Landing Zone
Once the endograft is sufficiently advanced, and both
contralateral gate position and appropriate gantry
angulation have been set, initial diagnostic imaging can
be obtained. The use of a contrast injector is required for
adequate opacification of visceral vessels. We prefer an
initial angiogram with a high rate and small volume of
contrast, typically 20 ml/s with a total volume of 20 ml of
full‐strength contrast. This should ensure visualization of
both renal arteries.
With the ostium of the renal arteries marked on screen
and the fluoroscopy table locked, initial deployment of
the graft can begin. Initial deployment should begin
above the target position, as many grafts tend to shift or
“jump” distally (Figure 5.3). This also allows for the graft
to be pulled down slowly during deployment, to a level
just below the renal artery. Depending on the device,
advancing the graft if it is positioned too low can prove
difficult. Some grafts, such as the Excluder, have a
repositionable proximal stent, which can be
reconstrained within the sheath by the operator to
ensure accurate deployment. The goal should be to place
the graft within 0–2 mm of the caudal edge of the lowest
renal. Maximal overlap will mitigate the risk of further
aneurysmal degeneration, graft migration, or type I
endoleak. It is important to know graft specifics, as
different grafts will have fabric located at varying
distances from the proximal stent.
Figure 5.3 Repeat contrast angiography prior to
complete deployment of the main body endograft can
ensure placement of the covered stent just below the
level of the lowest renal artery. The above picture
demonstrates filling of the left renal artery with the
proximal graft partially deployed.
After the proximal landing zone is established, the
endograft is further deployed until the contralateral gate
is deployed. At this point devices with suprarenal bare
stents can now be deployed to set the proximal landing
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zone in place before gate cannulation and limb
deployment.
Contralateral Gate Cannulation
For modular devices, the contralateral gate must be
cannulated prior to completion of the main body
deployment. This is however not the case in unibody
devices such as the AFX™ graft (Endologix, Irvine, CA,
USA). Several steps may assist the operator during main
body deployment: orientation of the gate slightly
anterior facilitates an easier angle of retrograde
cannulation from the ipsilateral iliac sheath, balleting or
crossing the limbs, and placement of the ipsilateral main
body limb up the more tortuous iliac side (Figure 5.4).
Figure 5.4 Cannulation of the contralateral gate can
prove challenging, as demonstrated by the still image
above. Operators must be facile with multiple catheters
of various orientations to help ensure success.
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