Добавил:
Sekretar
kiopkiopkiop18@yandex.ru
t.me/Prokururor I Вовсе не секретарь, но почту проверяю
Опубликованный материал нарушает ваши авторские права? Сообщите нам.
Вуз:
Предмет:
Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_3711_Библиотеки_им_академика_М_И_Перельмана
.pdf
e
21 Endovascular Repair oftheThoracic Aorta
https://t.me/med1917
a c
b
327
d
Fig. 21.1 Axial (a) and sagittal (b) contrast-enhanced CT images of the
thoracic aorta demonstrating a diverticulum of Kommerell (arrow).
Sequential DSA images of the thoracic aorta demonstrating the diverticulum of Kommerell (arrow) (c), the partially deployed Bolton Relay endo-
f
graft (d), and the fully deployed endograft with bare metal proximal
xation devices still restrained (e). Final angiogram of the thoracic aorta
(f) after successful deployment of the endograft. Note the left subclavian
artery was intentionally covered due to the proximity of the diverticulum
has proximal bare-metal stents which are designed specically for improved, stable deployment at the arch and does
not have signicant radial force. In contrast, the Relay NBS
Plus system is completely covered. The custom option allows
for an increased range of diameters (20–50mm), increased
taper options, including reverse taper grafts, and custom
graft lengths. Custom grafts require approximately 3weeks
to manufacture and deliver.
Modications of the original delivery account for the
“Plus” nomenclature of the currently available stents. The Plus
Delivery System has modications from the original design to
facilitate deployment of the stent graft around a smaller radius
of curvature. The inferior apices are left unclasped from the
delivery system catheter to allow the inferior portion of the
graft to expand at the beginning of the deployment. Two heatshaped nitinol “support wires” of the delivery system help to
ensure proper apposition of the graft to the inner curvature of
the aorta. Additionally, the leading end of the constraining
sleeve was enlarged to allow longitudinal adjustments of the
graft in its partially expanded state [22].
The grafts have diameters ranging from 24 to 46mm in
2mm steps accommodating vessel diameters of 19–42mm.
328
https://t.me/med1917
A. H. Fairchild and R. A. Hieb
Graft lengths range from 100 to 250 mm in 50 mm steps.
Both straight and tapered congurations are available. Current
delivery systems have an outer diameter (O.D.) of 22–26
French. Current modications are underway for the development of the next generation of the Bolton Relay (Relay Pro)
thoracic endografts which, if approved, will have a reduced
prole by 4 French across stents (19–22 French O.D.).
Funovics etal. evaluated the safety and efcacy of the Relay
thoracic stent graft in 22 patients between 2005 and 2007.
Patients were treated for aneurysms (n=13), PAU (n=7), and
dissections (n=2). Primary technical success was achieved in
20 of 22 patients, with one persistent type I endoleak and one
asymptomatic type II endoleak. No additional endoleaks were
observed in follow-up. One patient died 3days post stent placement secondary to malignant arrhythmia. One additional
patient died of nonaortic cause during follow-up [23].
Cook Zenith Thoracic Graft
Cook Medical has two thoracic endografts currently on the
market, the Zenith TX2 and the Zenith Alpha (Fig.21.2). The
Zenith TX2 endograft platform received FDA approval in
2008 for treatment of aneurysms or ulcers of the descending
thoracic aorta with nonaneurysmal aortic segments (xation
sites) proximal and distal to the aneurysm or ulcer of at least
25mm. The grafts have diameters of 28–42mm to treat aortic
diameters of 18–38mm (measured outer wall to outer wall).
The graft is composed of a Dacron graft with a nitinol
Z-stent exoskeleton. Active xation with barbs is present on
the proximal bare stents. The distal stent above the visceral
vessels is also bare. A modication from the prior generations is the addition of ProForm to allow greater conformability at the arch, limiting the “bird-beak” effect.
A prospective, nonrandomized comparison of 160
TEVAR patients treated with the Cook Zenith TX2 and 70
open surgical repair patients found similar mortality rates of
37% for both groups [24].
In 2008, American Association for Surgery of Trauma
(AAST) called for a “major and urgent need for improvement of available endovascular devices” for the treatment of
blunt thoracic aortic injury. Blunt traumatic aortic injury is
seen as the result of motor vehicle collisions and falls. As
such, the patient population is younger than the typical
patient requiring aortic endograft repair. On average, these
patients have smaller iliac access vessels, smaller aortic
diameters, and narrower aortic arch curvatures. In response
to this need, Cook Medical designed the Zenith Alpha.
The Zenith Alpha stent graft is constructed of self- expanding
nitinol stents sewn to a tightly woven Dacron. The device has a
lower prole introduction system than its predecessor the
Zenith TX2 (16F–20F compared to 20F–24F), can accommo-
date smaller and larger aortic diameters (18 to 46mm), and
accommodates an aortic arch with a radius of curvature of
20 mm. Unlike the fully covered Zenith TX2, the proximal
stent of the Alpha is bare. The cannula of the delivery system is
precurved to assist with proximal arch conformability.
The TRANSFIX trial is a prospective, nonrandomized,
noncomparative, single-arm, multicenter clinical trial conducted to assess the safety and efcacy of the Zenith Alpha
thoracic endograft [
reported a mean follow-up of 21months (range 18–1050days).
One patient died within 30days; however, it was not aortic
injury related. Four patients died after 30days, of which one
was related to aortic injury. Two cases of stroke occurred
within 30days, and no strokes were reported beyond 30days.
One patient required surgical conversion after failed reintervention for a proximal type I endoleak. Of the 31 patients
with available imaging 1-year postintervention, aortic injury
healing was conrmed in 96.8% (30/31) of patients. No type
I or type III endoleak or device migration was observed [
4, 25]. Recent mid-term follow-up
4].
Gore Conformable TAG
The Gore TAG endoprosthesis was the rst thoracic endograft approved by the FDA in March 2005. The current
Conformable TAG (cTAG) endoprosthesis (Fig.21.3) is the
third-generation iteration of this device and was approved in
2011. In 2012, the cTAG also became the rst stent graft
approved for traumatic transection. In 2013, the cTAG gained
FDA approval for aneurysms, transections, and acute and
chronic Type B dissections.
The device is made up of an expanded polytetrauoroethylene (ePTFE) tube with an external nickel-titanium (nitinol)
self-expanding stents adhered to the ePTFE. A partially
uncovered, barbless stent is present proximally with the
remainder of the graft completely covered. A circumferential
PTFE sealing cuff is present at each end. The device is constrained by ePTFE, which when deployed opens the graft
from the middle toward each end. This design is meant to
minimize the windsock effect that might otherwise be seen if
the graft were to open from the ends, toward the middle.
Evaluation of the newer cTAG’s deployment accuracy
was compared to the prior generation TAG device by Ito
etal. They found deployment accuracy at the time of implantation was signicantly better for the cTAG device as
compared to the TAG device (2.2±1.7mm vs. 4.4±3.0mm,
p <0.05). Additionally, fewer cases of bird-beaking were
seen with the cTAG (1in 12 cases vs. 8 of 20 cases) [26].
Devices are available in diameters of 21–45 mm and in
lengths of 10, 15, and 20cm. In addition, grafts are available
in a range of tapered sizes. The graft is engineered for 6–33%
oversizing.
ab
21 Endovascular Repair oftheThoracic Aorta
https://t.me/med1917
329
Medtronic Valiant
However, the Valiant was subsequently approved for complicated type B dissections in January 2014.
The Medtronic Valiant stent graft (Fig. 21.4) was initially
approved in April 2011 for the endovascular repair of fusiform aneurysms, saccular aneurysms, and penetrating ulcers
of the descending thoracic aorta. In November 2012, the
FDA expanded its approval to include all descending thoracic aortic lesions, with the exception of dissections.
There must be at least 20 mm of nonaneurysmal aorta
with a diameter range of 18–42mm proximal and distal to
the aneurysm in patients being treated for aneurysms or penetrating ulcers. Nonaneurysmal aortic diameters of
18–44 mm are approved for treatment of blunt traumatic
aortic injuries and 20–44mm for the treatment of dissections.
Fig. 21.2 Sagittal contrast-enhanced CT image (a) of the thoracic
aorta demonstrating a complicated dissection. The entry tear (dashed
arrows) is immediately distal to the left subclavian artery (star).
Intraprocedural IVUS image (b) demonstrates the IVUS catheter within
the true lumen and the false lumen marked by an asterisk. Initial intraprocedure digital subtracted angiogram (DSA) of the thoracic aorta (c)
with a multimarker pigtail ush catheter (solid arrows) within the true
lumen. DSA of the thoracic aorta (d) after the delivery of the Cook
c
Zenith Alpha endograft into the thoracic aorta prior to deployment to
assist with appropriate placement. Repeat DSA (e) after deployment of
the rst two stents of the graft. This allows for nal small adjustments
to the endograft positioning prior to complete deployment. Final DSA
(f) of the thoracic aorta after successful deployment of the endograft.
The left subclavian artery (star) was intentionally covered due to its
proximity to the dissection entry tear
330
https://t.me/med1917
A. H. Fairchild and R. A. Hieb
d
f
e
Fig. 21.2 (continued)
When treating dissections, there must be >20mm of landing
zone proximal to the entry tear, and the proximal extent of
the landing zone must not be dissected.
The graft is constructed of Dacron graft attached to a
series of sinusoidal-shaped, nitinol springs. There is no stiff
longitudinal bar, allowing for exibility and kink resistance
of the graft. The proximal graft consists of a partially uncovered eight-peak stent to assist in even distribution of the
radial force at the proximal seal. The outer diameter crossing
prole of the Medtronic Valiant is 24F and does not require a
sheath for delivery.
The VALOR II (Evaluation of the Clinical Performance
of the Valiant Thoracic Stent Graft System in the Treatment
of Descending Thoracic Aneurysms of Degenerative
Etiology in Subjects Who Are Candidates for Endovascular
Repair) was a prospective, nonrandomized, pivotal trial
enrolling 160 patients in 24 US sites between December
2006 and September 2009. The 30-day and 12-month data
ab
cd
21 Endovascular Repair oftheThoracic Aorta
https://t.me/med1917
331
was reported in 2012 [27]. Primary success with stent graft
deployment was achieved in 154 patients (96.3%).
Perioperative mortality at 30 days was 3.1%. Aneurysmrelated mortality was 4.0% at 12months. Stent graft migra-
tion was 2.9%, and rate of endoleak was 13.0% at 12months.
Through 12months, there were no ruptures, conversions to
open surgery, secondary procedures due to endoleak
>30days, or loss of stent graft patency [27].
Fig. 21.3 Sagittal (a), coronal (b), and axial (c, d) contrast-enhanced
CT images demonstrating a mobile thrombus (arrow) of the middescending thoracic aorta. DSA (e) and native (f) images of the
descending thoracic aorta after deployment of the Gore Conformable
TAG endograft covering the mobile thrombus
332
https://t.me/med1917
ef
A. H. Fairchild and R. A. Hieb
Fig. 21.3 (continued)
Preprocedural Considerations
Access
The most frequently encountered complication during thoracic stent graft trials has been access-related complications.
Iliac artery morphology is essential to delivering the device
percutaneously into the aorta. Factors important to the successful delivery of the stent without damage to the iliac artery
include arterial tortuosity, intraluminal diameter, and calcications [28, 29]. The issue of iliac diameter becomes particularly important in female patients, who have signicantly
smaller iliac arteries than men and more frequently require an
iliac conduit for access [30]. Iliac artery injuries are more
commonly seen in TEVAR than EVAR due to the larger delivery systems and higher percentage of women treated [31].
No absolute cut-offs or specic predictors for tortuosity,
calcication, or diminished caliber exist; however, several
authors have evaluated these parameters in reviews of their
iliac rupture experience during endograft placement.
Fernandez et al. reported a series of 369 EVARs and 67
TEVARs with 18 ruptured iliac arteries in 17 patients [32].
Patients with rupture in this series had greater calcication of
the common iliac artery (66% vs. 26.5%), greater aortoiliac
angulation (45° vs. 32°), and smaller external iliac caliber
(8.0 vs. 8.9 mm). All ruptures occurred with the use of a
delivery system of 20 French or greater [32].
Importantly, patients with intraprocedure iliac rupture
have longer length of stay postprocedure and a higher
procedure- related mortality. One study reported a
procedure- related mortality of 11.8% in patients who sustained an iliac rupture compared to 9.8% in patients who
ab
21 Endovascular Repair oftheThoracic Aorta
https://t.me/med1917
333
cde
Fig. 21.4 A 71-year-old male patient presenting with chest pain and
shortness of breath. Axial (a) and coronal (b) contrast-enhanced CT
images of the thoracic aorta demonstrating a multilobed pseudoaneurysm (arrow) of the proximal descending aorta surrounded by the left
upper lobe mass/inltrate. DSA (c) of the thoracic aorta demonstrating
contrast lling the pseudoaneurysm (arrow). DSA (d) immediately following the deployment of a Medtronic Valiant stent graft and a subsequent volume-rendered CT image (e) of the thoracic aorta demonstrating
exclusion of the pseudoaneurysm
did not sustain an iliac rupture [32]. No intraprocedure
deaths were reported [32].
Conversion to an open aortic and iliac repair has been associated with mortality rates as high as 22% [32, 33]. For this
reason, endovascular iliac repair is preferred when feasible.
Availability of the appropriate covered stents for iliac repair is
an important preparatory step in endovascular aortic repair.
Identication ofLanding Zones
The Society for Vascular Surgery published reporting standards for TEVAR, in which it identied 11 landing zones for
management of aortic disease (Fig. 21.5) [34]. Using this
standardization assists in evaluating the complexity of a procedure as well as the length of aorta needed to be covered.
334
https://t.me/med1917
A. H. Fairchild and R. A. Hieb
Device Sizing
Accurate measurements of the aortic diameter and length are
imperative for appropriate device sizing. This is facilitated
by a high-quality CTA with multiplanar reformats but may
2
require additional reconstructions on a 3D workstation for
precise measurements. Sobocinski etal. compared outcomes
12
3
of patients who underwent endograft placement based on
measurements from axial images versus those measured
using a 3D workstation with multiplanar reformats and centerline analysis. After a 2-year follow-up period, the type 1
endoleak rate for grafts sized with axial images was 8.7%
and 1.4% (p=0.004) for grafts sized with 3D workstation
0
4
assistance [35].
While each manufacturer has specic guidelines, in general, a stent graft should be oversized by approximately 20%.
Too little oversizing can result in a type I endoleak and/or
migration of the endograft from its intended location. Too
much oversizing can result in graft infolding.
Spinal Cord Ischemia
5
Fig. 21.5 Landing zones of the thoracic aorta. Zone 0: Proximal to
innominate artery. Zone 1: Proximal to the left common carotid artery.
Zone 2: Proximal to the origin of the left subclavian artery. Zone 3: The
proximal descending thoracic aorta (<2cm from the left SCA). Zone 4:
Two centimeter distal to the SCA and extends to the proximal half of
the descending thoracic aorta (approximately T6). Zone 5: Distal half of
the thoracic aorta to celiac artery
Importantly, not all aortic pathology should be treated
the same. While a device’s recommended seal zone is
2–3cm is adequate for some aortic pathology, a longer seal
zone may be preferable, for example, when the graft would
otherwise end in a particularly angulated segment of aorta
or in the case of an atherosclerotic aneurysm. While a segment of aorta immediately abutting the aneurysm may
appear normal, it is usually involved in the same degenerative process as the aneurysm itself. Later degeneration of
the landing zone aorta can lead to stent graft failure.
However, the desire to cover more aorta needs to be balanced with the risk of spinal cord ischemia with excessive
coverage.
Endovascular repair of descending thoracic aortic pathologies has grown primarily due to lower rates in periprocedural
major complications including spinal cord ischemia (SCI)
[36]. However, SCI rates still range between 2% and 7% for
TEVAR [36, 37]. Risk factors for SCI after TEVAR are multifactorial and include length of aortic coverage, prior
abdominal aortic aneurysm repair, hypotension, iliac artery
injury, renal failure, and left subclavian artery coverage [38].
There are several important aspects of spinal perfusion
unique to the endovascular repair of the aorta not seen in
open surgery. First, there is permanent loss of intercostal perfusion as they are not reimplanted as in open surgical repair.
Second, while intraprocedural hemodynamic changes and
prolonged hypotension are less severe during endovascular
repair, low blood pressure may be benecial in precise device
landing in difcult anatomy [39]. Finally, guidewire and
catheter manipulation increases the risk of embolic insult
during endovascular thoracic repair.
Preoperative placement of a lumbar cerebrospinal uid
(CSF) drain is standard in open thoracic aortic repair; however, their use is less well dened in the setting of TEVAR
[40]. Current guidelines from multiple societies advocate
drainage in the case of long-segment descending thoracic
aortic coverage or in patients with prior abdominal aortic
repair [41]. This data is based on open surgical experience,
with little available data demonstrating a reduction in SCI in
patients after TEVAR [40]. As a result, institutions vary
greatly in the implementation of these recommendations.
21 Endovascular Repair oftheThoracic Aorta
https://t.me/med1917
335
While the potential benet of drain placement can be
huge, the placement of these drains is not free of
complications. Subdural hematomas occur in approximately
3.5% of patients after thoracic aortic aneurysm repair with
CSF drainage with associated mortality up to 67% [42].
Other complications include spinal headache, bleeding, CSF
leak, meningitis, intracranial hemorrhage, nerve injury, and
epidural hematoma [40]. In patients at low risk for SCI, the
placement of a drain may outweigh the risk of drain placement, as only 1in 300 (0.3%) patients without a drain sustain
permanent SCI [40].
Importantly, SCI can present immediately or in a delayed
fashion. While some patients have symptoms at the time of
device implantation, one third of patients will have onset of
symptoms hours, days, weeks, or months later [43].
Evaluation of 67 consecutive patients who underwent endovascular repair of descending thoracic aortic lesions reported
5 (7.5%) patients who developed SCI.Three (60%) of these
patients presented with delayed symptoms [44]. It is postulated that delayed symptoms may be due to thrombosis of a
spinal cord artery or compromise of a marginal existing
blood supply [45].
Left Subclavian Artery Coverage
The left subclavian artery (LSA) is typically the most distal
of the arch vessels. It gives rise to the left thyrocervical trunk,
left internal mammary artery, and the left vertebral artery.
Occlusion of the proximal LSA will result in reversal of ow
in the left vertebral artery which becomes the dominant
blood supply to the subclavian artery. The posterior cerebral
circulation then relies on an intact circle of Willis.
Complications following acute occlusion of the LSA include
ischemia of the left upper extremity, stroke, spinal cord ischemia, endoleak, and myocardial ischemia. A meta-analysis
of 51 studies found the risk of arm ischemia to be 6%, spinal
cord ischemia 4%, vertebrobasilar ischemia 2%, anterior circulation stroke 5%, and death 6% when the LSA is covered
during TEVAR [46].
Upper Extremity Ischemia
The physical manifestations of acute left subclavian artery
occlusion during TEVAR range from asymptomatic diminution of the left arm blood pressure to left upper extremity rest
pain [47]. All patients undergoing LSA coverage should be
instructed to have blood pressures taken in the right arm as
the left arm will provide falsely low readings. The magnitude
of this pressure reduction does not, however, correlate with
the development of symptoms [48].
When patients do present with symptoms, rest pain is
rare. More commonly, patients may note a cool sensation of
the left hand, temperature sensitivity, or exercise-induced
claudication [
498 patients (10%) developed symptoms of upper extremity
ischemia [49]. Only 20 (4%) patients required subsequent
revascularization due to the severity of their symptoms [49].
Klocker etal. evaluated left arm function and quality of
life after TEVAR with and without LSA coverage in 138
patients. Seventy-three (52.9%) patients had LSA coverage
and a single patient required left carotid to subclavian bypass
postprocedure for ischemic symptoms with subsequent resolution of symptoms. All patients were evaluated based on the
Disabilities of the Arm, Shoulder, and Hand (DASH) questionnaire and the 12-item Short Form Health Survey. Patients
were followed up for a mean of 4.1years (±3.7). Patients
with and without LSA coverage had similar Physical
Component Summary and Mental Component Summary
health scores (12-Item Short Form Health Survey) as well as
DASH scores [50].
Gombert et al. assessed upper extremity pain and dysfunction using the DASH questionnaire in a cohort of 46
patients suffering blunt aortic injury treated with TEVAR.The
results of the DASH questionnaire were available for 30 of
the 46 patients (65.2%), of which 22 (73.3%) received LSA
coverage at the time of their procedure. The patients
responded a mean of 5.1years (range 0.5–14.9) after their
trauma. Comparison of the groups with and without LSA
coverage revealed no signicant difference (two-sided
p-value: 0.3513) [
An anomalous right subclavian artery, where the right
subclavian artery arises distal to the left subclavian artery, is
the most common aortic arch anatomic variation occurring in
up to 2% of the population [52]. Published experience with
anomalous right subclavian artery coverage is limited but
demonstrates similar sequelae as coverage of the left subclavian artery [47, 53].
47]. A meta-analysis of 20 studies found 51 of
51].
Stroke
Stroke may result from several mechanisms during endovascular repair of the thoracic aorta. Most are the result of aortic
wall atheroemboli dislodged during wire and device manipulation during the procedure [54]. Alternatively, stroke can
occur in the setting of a low ow state such as hypotension.
There is debate on whether ischemia in the left vertebral
artery distribution occurs after coverage of the left subclavian artery (LSA) during TEVAR as much of the available
data is derived from single institutional series [55].
A meta-analysis of 25 series directly comparing coverage of the LSA versus more distal deployment found an
overall stroke rate of 7.4% (87 of 1177) following LSA coverage during TEVAR.The overall stroke rate for stent grafts
with zone 3 or 4 deployment was 4.0% (107 of 2661,
p<0.0001) [55].
An evaluation of 27 series providing data on LSA revascularization prior to coverage of the LSA found an overall
336
https://t.me/med1917
A. H. Fairchild and R. A. Hieb
stroke rate for TEVAR following LSA coverage of 4.8% (59
of 1237). When the LSA was covered without
revascularization, the stroke rate was 5.6% (46 of 824) compared to 3.1% (13 of 413, p=0.0657) who underwent revascularization with carotid-subclavian bypass or
subclavian-carotid transposition prior to LSA coverage [55].
Adding to this, a review of 606 patients in the European
Collaborators on Stent/Graft Techniques for Aortic Aneurysm
Repair (EUROSTAR) registry found coverage of the LSA
without revascularization resulted in a signicantly higher
incidence of spinal cord ischemia or stroke when compared
to patients undergoing LSA revascularization prior to
TEVAR (8.4% vs. 0%; p=0.049) [56].
Several authors have demonstrated that coverage of the
LSA is an independent risk factor for posterior stroke. Rizvi
etal. presented a meta-analysis demonstrating LSA coverage
was associated with increased risk for vertebrobasilar ischemia with an odds ratio of 10.8 [46]. Similarly, Ullery etal.
presented a series of 530 patients where LSA coverage was
an independent risk factor for posterior stroke with an odds
ratio of 6.11 [57].
As a result of these reports, the Society of Vascular
Surgery now recommends preprocedural LSA revascularization prior to all elective TEVAR cases despite the low-quality
evidence available (GRADE 2, level C) and consideration
for preprocedural LSA revascularization in the setting of
acute aortic syndromes [58].
Importantly, not all strokes seen after LSA coverage are
posterior strokes. A meta-analysis of 12 series describing the
location of strokes after LSA coverage reported 42 strokes in
543 patients (7.7%). Eleven of the 42 strokes (26.2%) were
posterior strokes. The remaining 31 strokes (73.8%) were
anterior embolic or diffuse embolic strokes [55]. As previously mentioned, it is postulated that wire and graft manipulation in the aortic arch results in embolic stroke by dislodging
debris [54], rather than coverage of the LSA itself.
Spinal Cord Ischemia
Coverage of the LSA increases the risk of spinal cord ischemia. Please refer to the above discussion of spinal cord
ischemia for a detailed discussion.
Endoleak
Coverage of the LSA with an endograft often acts as a “ush
occlusion” of the artery at its origin. The LSA will frequently
thrombose to its rst branch, typically the vertebral artery, by
1month [47]. The LSA can however be a source of endoleak.
This is generally seen in cases where the LSA is involved in
the aortic lesion or where a left carotid-subclavian artery
bypass is present without proximal occlusion of the LSA
[47]. In a retrospective review of 200 patients undergoing
TEVAR, the presence of a carotid-subclavian artery bypass
graft performed in cases of LSA coverage was associated
with the presence of an endoleak (p=0.0001) [59].
Myocardial Ischemia
An important consideration for patients undergoing TEVAR
is prior surgical history. The left internal mammary artery is
a frequent autogenous arterial conduit used to the left anterior descending during coronary artery bypass surgery.
Subsequent acute occlusion of the LSA can result in a coronary steal like entity and life-threatening myocardial ischemia [47].
Celiac Artery
In some instances, the distal landing zone is inadequate without coverage of the celiac artery. In a patient with adequate
collateral circulation between the celiac axis and the superior
mesenteric artery (SMA), the celiac artery can be covered
safely during TEVAR [60, 61]. Adequate collateral circulation should be assessed with formal angiogram of the celiac
and SMA.In patients without adequate collateral circulation,
either open revascularization or endovascular placement of a
periscope graft is a means of extending the distal seal zone
while preserving visceral perfusion [62].
Intraprocedural Considerations
Intravascular Ultrasound
Intravascular ultrasound (IVUS) is an imaging tool which
provides real-time intraluminal assessment and can allow for
more accurate diameter measurements. This is a particularly
useful tool in the setting of blunt aortic injury (BAI). As a
whole, patients presenting with BAI are young with nonatherosclerotic, compliant aortas. As a result, the aortic diameter can vary greatly during the cardiac cycle [63]. Additionally,
the patients often undergo marked hemodynamic changes
during resuscitation which can also impact aortic diameter
[64].
Shi et al. reviewed 41 patients undergoing TEVAR for
BAI.IVUS was used in 13 cases, and as a result of the IVUS
measurements, the implanted graft was changed in 6. Of
note, the greatest difference between CT and IVUS measurements was noted in the proximal aorta in cases where the
LSA was covered [65].
IVUS has additional utility in the treatment of aortic dissections. Koschyk etal. evaluated the utility of IVUS in 26
patients with Stanford type B dissections. They found that
IVUS differentiate between true and false lumen intraprocedure as well as the location of the entry tear. This proved
Соседние файлы в папке Библиотека им академика М.И. Перельмана