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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_3925_Библиотеки_им_академика_М_И_Перельмана
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272 Brinster et al.
of tortousity, brachiofemoral access may be required to perform “body-flossing”
with an appropriately stiff wire. Typically, a 5 Fr sheath with a long catheter is
placed into the aortic arch and then into the descending aorta. A long stiff wire,
such as a 450 cm SS Guidewire (Boston Scientific), is guided from the brachial
and retrieved through the femoral artery. Gentle traction on both the brachial and
femoral sites will straighten out the tortuosity. Of note, a long catheter must be
placed through the brachial artery into the aorta to prevent excessive trauma by the
stiff wire along the arch and innominate vessels.
At the completion of the deployment and ballooning of the thoracic stent
graft, the entire route of access must be carefully examined to ensure that there has
been no injury. The stiff guidewire used to position the thoracic endograft, should
be left in place as the sheaths and remaining endovascular materials are removed.
A smaller sheath should be reinserted and the iliac vessels should be retrogradely
injected to check for thrombus, dissection, or complete avulsion.
The removal of the large sheath, especially when inserted with some force
and manipulation, is a particularly dangerous period when injury may occur. There
have been numerous reports of successful thoracic endografting with a sheath
removed having a complete iliac artery avulsed on the sheath (Fig. 2). At the time
Figure 1 Retroperitoneal access of common internal iliac using double pursestring and
Seldinger technique. Source: From Ref. 127.
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Endovascular Thoracic Aortic Stent Grafting 273
of recognition, a stiff wire through this injured artery may be life saving, allowing
insertion of an occluding balloon proximally to control potentially life threatening
bleeding. In addition, both the blood pressure and heart rate should be carefully
monitored during removal and completion of the endovascular procedure for signs
of an occult injury.
Landing Zones
The proximal aorta is divided into landing zones as illustrated in Figure 3. Proximal
landing in Z0 and Z1 are unacceptable due to the necessary occlusion of the left
common carotid artery in Z1 and the innominate artery in Z0. Proximal landing in
Z2 is commonly used with either partial or total occlusion of the left subclavian
Figure 2 “Iliac on a stick.” Figure of large sheath with avulsed external iliac which
occurred after successful stent deployment.
Figure 3 Proximal landing zones of the aorta. Z0: ascending aorta to the distal aspect of
the innominate artery origin. Z1: distal to the innominate artery origin including the left
common carotid artery origin. Z2: distal to the left common carotid artery origin including
the left subclavian artery origin. Z3: proximal third of the descending thoracic aorta distal
to the left subclavian artery origin. Z4: remainder of the supradiaphragmatic descending
thoracic aorta. Source: From Ref. 67.
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274 Brinster et al.
artery. Z3 landing is dependent on the exact anatomical neck at the arch. Proximal
landing in Z3 can lead to angulation of the graft, which provides inadequate
sealing of the proximal graft along the lesser arch and “bird beaking” or “stove
piping” graft placement, with resultant high incidence of type II endoleaks (Fig. 4).
Z4 landing is usually straightforward due to the lack of angulation and distance
from the arch vessels.
Presently, the proximal and distal landing zones must be of an appropriate
diameter to allow for stent grafting with available devices. The safe aortic dia-
meter at the time of this writing is between 19 mm and 43 mm depending on the
different devices available. Generally, devices can be oversized (compared to the
diameter of the landing zone) between 5% and 18%, depending on presenting
aortic pathology.
As discussed, the proximal landing zone of the aorta must be carefully
examined on preoperative imaging workup. The goal is to create a good seal of
15–20 mm length between the graft and the aortic wall on a disease-free, non-
tapered, nonangulated portion of the aorta. There should be adequate length of
the proximal landing zone, minimal angulation, minimal tortuosity, and minimal
calcification (Fig. 5). Angulation of the aortic arch is acceptable if the inner radius
is >35 mm and the outer radius is >70 mm (Fig. 6). These parameters allow
adequate conformation of the aortic stent graft to the arch.
Since Z2 is often the site of best proximal landing to avoid excessive
angulation and tortuosity, the management of the left subclavian artery requires
preoperative planning. Possible complications of covering the left subclavian
artery include verterbrobasilar artery insufficiency or stroke, left arm ischemia,
Figure 4 Type I endoleak (periprosthetic) occurs at the proximal and/or distal attachment
zones. Type II endoleak is caused by retrograde flow from patent lumbar or
inferior mesenteric arteries. Type III endoleak arises from a defect in the graft fabric, inad-
equate seal, or disconnection of modular graft components. Type IV endoleak is due to
graft fabric porosity, often resulting in a generalized mild blush of contrast within the aneu-
rysm sac. Source: From Ref. 128.
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Endovascular Thoracic Aortic Stent Grafting 275
Figure 5 (A) Angiogram and diagram of angulated arch without suitable proximal land-
ing zone with high risk of Type I endoleak from “stove piping” of the graft (arrows).
(B) Angiogram, which demonstrates a longer proximal landing zone without excessive
angulation. (C) Successful stent graft placement in proximal landing zone with no endoleak.
Figure 6 Inner radius should be <35 mm and outer radius >70 mm.
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276 Brinster et al.
or ischemia of the heart in patients with a previous left internal mammary artery
to left anterior descending coronary artery bypass graft.
An evaluation of the right vertebral artery and the adequacy of the circle of
Willis are crucial when planning to cover the left subclavian artery. In those
patients with inadequate collaterals through the circle of Willis, a stenotic right
vertebral artery, or a dominant left vertebral artery, strong consideration should be
made to bypass the left subclavian artery prior to covering. One option is to trans-
pose the left subclavian artery to the left common carotid artery with oversewing
of the proximal left subclavian artery. Another option is to bypass from the left
common carotid artery to the left subclavian artery with an 8 mm Dacron graft.
Either surgical ligation of the proximal left subclavian at the time of bypass or
staged coil embolization of the proximal left subclavian artery at the time of graft
delivery may be used. Bypass of the left subclavian may be preferable because it
avoids any mediastinal dissection and there is no interruption of antegrade flow to
the vertebral artery or internal mammary artery branch vessels (Fig. 7).
Evaluation of the distal landing zone also requires careful preoperative
workup. The distal landing zone should again have 15–20 mm of normal aorta
with minimal calcification, angulation, and tapering. The celiac artery is the first
distal branch vessel that must be avoided. Therefore, the length of the aortic graft
must be correctly planned. Enough graft length should cover the aortic pathology
while avoiding excessive coverage of the descending thoracic aorta. The goal is
to preserve the distal intercostal arteries and perfusion to the spinal cord. When
planning the length of the graft, the outer curvature of the aorta is assumed to be
the correct area to measure (Fig. 8). However, the graft may lie along the lesser
curvature instead. Therefore, a strategy must be developed to select a graft, which
will be able to work in either the greater curvature or lesser curvature.
Figure 7 (A) Image prior to translocation of left subclavian artery. Note the inadequate
length of proximal landing zone. (B) Same patient after translocation of left subclavian
artery to the left common carotid artery and status post successful stent graft placement.
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Endovascular Thoracic Aortic Stent Grafting 277
Figure 8 Demonstration of the possible maximum (hollow arrow) and minimum (long
solid arrow) course that stent graft may be positioned.
RESULTS OF TEVAR IN DESCENDING THORACIC
AORTIC ANEURYSMS
Three United States clinical trials have examined the use of endovascular aortic
stent graft technology in the treatment of descending thoracic aortic aneurysms.
The three devices (Medtronic Talent, Gore TAG, and Cook Zenith TX2) have also
been used extensively worldwide. Results from the U.S. clinical trials as well as
results from the worldwide experience have been encouraging, prompting investi-
gators to expand the role of TEVAR to acute thoracic aortic pathologies. The three
U.S. trials will briefly be discussed.
VALOR Trial
The Medtronic VALOR trial is a prospective, multicenter, nonrandomized, obser-
vational trial evaluating the use of the Medtronic Talent thoracic stent graft system
in the treatment of thoracic aortic pathology. One-year data for the VALOR trial is
expected soon. The trial consists of three groups: (i) the test arm, (ii) the registry
arm, and (iii) the high-risk arm. The test arm consists of patients with the diagnosis
of thoracic aortic aneurysms who are considered surgical candidates for traditional
open repair with low to moderate risk [based on society of vascular surgery (SVS)/
international society of cardiovascular surgery (ISCVS) criteria]. At least 20 mm of
normal aortic neck at the proximal and distal landing zone is required. Enrollment
of 195 patients is complete, and one-year follow-up data (rate of mortality and
successful aneurysm treatment) is awaiting accrual prior to FDA disclosure. The
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278 Brinster et al.
registry arm (27 patients) included patients considered to be open surgical candi-
dates with low to moderate risk but either proximal or distal neck less than 20 mm
in degenerative aneurysm, chronic pseudoaneurysm, or chronic dissection.
The results of the high-risk arm were recently presented at the SVS annual
meeting (June 2005, Chicago, U.S.A). This arm consists of SVS group 3, or nonsur-
gical, candidates with thoracic aortic pathology including degenerative aneurysms
(82%), chronic dissection with aneursymal formation (9%), pseudo aneursym (9%),
traumatic injury (6%), and complicated type B dissection (4%). A total of 150
patients were accrued in this arm with a mean age of 73. Procedural success rate was
98%, with a 30-day mortality of 8.4%. The incidence of neurologic complication
was 8% for stroke and 5.5% for paraplegia. At one and six months, the endoleak rate
was 12% and 10% respectively, with a secondary reintervention rate of 2.8% at six
months. In this arm, 15% of patients required surgical placement of a conduit for
arterial access for device deployment. The clinical experience with the Talent device
worldwide as well as in the VALOR trial has been summarized in Table 2.
TAG Trial
The Gore TAG 99-01 trial is a Phase II, U.S. multicenter investigation comparing
the Gore TAG endoprosthesis (W.L. Gore, Flagstaff, Arizona, U.S.A.) in the
treatment of descending thoracic aortic aneurysms to an open surgical control
group. Between September 1999 and May 2001, 140 patients with descending
thoracic aortic aneurysms were enrolled from 17 sites in the United States.
All patients were required to have at least 2 cm length of nonaneurysmal aorta
distal to the left carotid and proximal to the celiac axis. At the same centers,
the open surgical control cohort enrolled 94 patients. Forty-four patients were
concurrent controls and 50 were historically and retrospectively acquired by
selecting the most recent surgical patients in reverse chronological order.
The results are summarized in Table 3. Thirty-day mortality was 2.1% and
11.7% in the Gore TAG group and the open surgical control group, respectively.
Spinal cord ischemia was 2.9% in the Gore TAG group versus 13.8% in the control
group. The mean length of intensive care unit stay and total length of hospital stay
were significantly shorter in the Gore TAG group (5).
STARZ-TX2
The study of thoracic aortic aneurysm repair with the Zenith-TX2 (STARZ-TX2)
trial is a nonrandomized, open label, efficacy study evaluating the safety and
effectiveness of the Cook Zenith TX2 (Bloomington, Indiana, Massachusetts,
U.S.A.) endoprosthesis in the treatment of thoracic aortic aneurysms. The primary
outcome of the study is 30-day survival. Enrollment began in March 2004 with an
expected enrollment of 275 patients. The trial is currently ongoing. The study is
near completion with closure of the trial expected soon.
In summary, TEVAR is an evolving technology for the treatment of thoracic
aortic pathology. Preliminary data demonstrate that the short- and mid-term outcomes
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Endovascular Thoracic Aortic Stent Grafting 279
Table 2 Summary of Medtronic Talent Experience
Mean Procedural 30-Day
Total follow up Patients with success Paraplegia mortality
Author patients (months) TALENT rate (%) (%) Endoleak Reintervention (%) Survival
VALOR (high- 150 12 150 98 5.5 10% at 2.8% at 6 mos 8.4 —
risk group) 6 mos
TTR 457 24 457 98 1.7 9.6% 8% at 1 yr, 5 91% at 1yr,
19% at 3 yrs, 85% at 3 yrs,
30 at 5 yrs 77%at 5 yrs
Zipfel (2006) 172 — 123 92 1 — — 9.7 —
Appoo (2005) 99 — 63 100 2 23% 10% 5 85% at 1yr,
71% at 3 yrs,
52% at 5 yrs
Criado (2005) 186 40 186 96.7 4.3 15% at 15% 4.7 62.5% at
30 days 40 mos
Farber (2005) 22 12.5 19 100 9 4% — 4.5 —
Riesenman (2005) 50 9 45 96 0 20% 14% 8 79.4% at 3 yrs
Scheinhert (2004) 31 15 29 100 0 0% 0% 9.7 90% at 17 mos
Fattori (2003) 70 25 67 97 0 7% 4% 8 91% at 25mos
Ellozy (2003) 84 15 62 90 4 5% — 6 67% at 40 mos
Herold (2002) 34 8 33 100 0 0% — 2.9 88.7% at 8 mos
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280 Brinster et al.
with both the Medtronic Talent and Gore TAG endoprosthesis compare favorably
with the conventional open repair for the treatment of descending thoracic aortic
aneurysm. The results of the STARZ-TX2 trial are not available yet. However, world-
wide experience with the Zenith TX2 endoprosthesis has been equally encouraging.
The durability of TEVAR remains unclear. Further investigation with long-term
followup comparing TEVAR and conventional surgical repair is needed before
definitive conclusions can be made.
ACUTE AORTIC SYNDROME
Although TEVAR for elective repair of descending thoracic aortic aneurysm has
been performed worldwide with increasing frequency, it is the potential role of
TEVAR in acute thoracic aortic pathologies that has gathered increasing interest
and fits most closely with the subject matter of this book. Through recent surgical
advances, morbidity and mortality with elective conventional surgical repair of
thoracic aortic aneurysms has been reduced to acceptable levels. However,
mortality for emergent thoracic aortic pathologies remains substantial. The mini-
mally invasive nature of TEVAR renders this a potentially attractive surgery for
this high-risk group of patients. The emerging role of TEVAR for acute aortic
diseases is discussed in the following section.
Type A Dissection
Ascending aortic dissection (Stanford type A), is the most common lethal aortic
condition requiring emergent surgical management (6–9). The estimated worldwide
Table 3 Early Postoperative Outcomes (Gore TAG 99–01)
Endovascular (%) Open surgical P-value
Mortality–30-day or in hospital 2.1% (n = 3) 11.7% (n = 11) <0.001
Respiratory failure
a
4% 20% <0.001
Post op MI 0% 1% 0.40
Renal failure
b
1% 13% <0.04
Wound infection/dehiscence 4% 11% 0.07
GI complication (ileus, bowel 2% 6% 0.16
ischemia, or bowel obstruction)
Peripheral vascular complications
c
14% 4% 0.015
Neurologic complications
CVA 4% (n = 5) 4% (n = 4) 1.00
Paraplegia/paraparesis 3% (n = 4) 14% (n = 13) <0.003
Mean ICU length of stay (days) 2.6 ± 14.6 5.2 ± 7.2 <0.001
Mean length of hospital stay (days) 7.4 ± 17.7 14.4 ± 12.8 <0.001
a
Mechanical ventilation >24 hrs post op or need for reintubation.
b
≥30% rise in base line creatinine level.
c
Includes embolism, thrombosis, and vascular trauma.
Source: From Ref. 5.
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Endovascular Thoracic Aortic Stent Grafting 281
prevalence is 0.5 and 2.95 per 100,000 per year. In the United States, it is esti-
mated that the prevalence is between 0.2 and 0.8 per 100,000 per year, resulting in
approximately 2000 new cases per year (10). These estimates may be low, with
one autopsy series demonstrating the antemortem diagnosis was made in only
15% of patients (11). Analysis that takes this factor into account results in an
estimate of approximately 6000 new cases per year in the United States.
The standard of care for the treatment of type A aortic dissection is surgical
therapy. The present surgical strategy is designed to prevent (i) rupture, (ii) heart
failure related to acute aortic valve insufficiency, (iii) coronary malperfusion,
and (iv) cerebral malperfusion, or stroke. Recent advances in surgical manage-
ment of acute type A dissection have resulted in significantly lower morbidity and
mortality. Recent series demonstrated mortality rates ranging from 9% to 25%
(12–19). Five-year survival following type A dissection repair ranges from 71% to
89% (13,17,20).
Proximal operative strategy (i.e., the choice of surgical technique for man-
aging the proximal end of the dissection) does not appear to have significant impact
on morbidity and mortality. Driever et al. (17) noted no difference in survival or
stroke rate when comparing aortic valve replacement (AVR) with supracoronary
ascending aortic replacement and valve resuspension with supracoronary aortic
replacement at five and 10 years. Lai et al. (16) similarly reported no difference
in six year survival between patients treated with composite valve conduit (65%),
AVR and supracoronary replacement (45%), and valve resuspension and supra-
coronary aortic replacement (69%). In the largest reported single-center experience
(295 patients treated between 1990 and 2003 for acute type A aortic dissection),
Kallenbach et al. (13) showed no difference in outcome with respect to mortality,
neurological complications, and five year survival when comparing composite valve
conduit, supracommissural replacement, and valve-sparing aortic root replacement.
Due to the improved surgical outcome and the inherent complexity of
proximal repair, the application of endovascular aortic stent graft therapy has been
limited in acute type A dissection. A few case reports have demonstrated feasibility
of endovascular repair of type A dissection in a very small number of patients
(22–24). The role of endovascular stent graft therapy in the treatment of acute
type A dissection remains unclear.
In an adjunctive role, investigators have reported the concomitant use of an
aortic stent graft in the descending thoracic aorta during conventional open type A
dissection repair—in an effort to obliterate the distal thoracic dissection and pre-
vent chronic aneurysmal dilatation. The long-term results of these “hybrid”
procedures remain to be determined.
Type B Dissection
Although there is consensus that ascending aortic dissections should be managed
by urgent surgical repair, controversy currently exists regarding the optimal thera-
peutic strategy for descending thoracic aortic dissections (Stanford type B).
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