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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_3955_Библиотеки_им_академика_М_И_Перельмана.pdf
Stent-Grafting of the Thoracic Aorta 211
Indications
Urgent Indications
• Aortic rupture:
b
Aneurysm
b
Aortic trauma
b
Aortic dissection, intramural hematoma, and PAU
• Non-ruptured symptomatic atherosclerotic aneurysms
• Non-ruptured traumatic aortic pseudoaneurysms
• Visceral ischemia due to true lumen collapse (dynamic compression) in aortic
dissections
• Persistent thoracic pain in the presence of acute type B dissection or intramural
hematoma
• Enlarging aorta on consecutive CT scans in acute aortic syndrome
Elective Indications
• Atherosclerotic aneurysm larger than 5.5 cm.
b
5 cm in women or small adults
• Aortic dissection with an aortic diameter greater than 5.5 cm.
• Chronic traumatic pseudoaneurysm greater than 5.5 cm
Extended Indications
The technique can be extended to treat lesions involving the aortic arch and
thoracoabdominal pathology by the following techniques:
• Hybrid procedures − these involve elective bypass of the supra-aortic or abdom-
inal visceral vessels followed by the insertion of endografts.
• The use of branched or fenestrated endografts.
These complex procedures are outside the scope of this chapter.
Contraindications
The following are relative and not absolute.
• Marfan syndrome or other connective tissue diseases
• Systemic infection
• Unfavourable anatomy
212 J.-P. Beregi and M. Midulla
Patient Preparation
• Procedures are either performed under general or regional anesthesia. Therefore,
patients are prepared in the standard manner for the type of anesthesia they
require.
• Imaging of the carotid and vertebral arteries is sensible if the stent-grafts have to
be deployed close to these vessels, or if the supra-aortic vessels require elective
bypass to extend the proximal landing zones.
Relevant Anatomy
The key anatomical inclusion criteria for TEVR are
• The presence of landing zones of normal aorta proximal and distal to the lesion
to provide a seal between the endograft and the aortic wall and prevent leakage
into the aneurysm or false lumen.
• Adequate caliber access vessels.
Proximal Landing Zone
Diameter:
• The maximum diameter landing zone is decided by the maximum available
endograft diameter − currently 46 mm (Valiant, Medtronic, Santa Rosa, CA).
• Endografts should be oversized by 10–20% to achieve an adequate seal.
• Therefore, the maximum diameter of the landing zone is 42 mm.
Length:
• 20 mm between the lesion and the left subclavian artery is optimal for straight-
forward procedures.
• If the lesion is more proximal and close to the aortic arch and supra-aortic vessels,
one or more of these vessels can be covered after pre-procedural elective bypass
of the relevant supra-aortic vessels.
• Coverage of the left subclavian artery without bypass was previously performed,
but this practice is now known to be associated with increased stroke and
paraplegia risk.
Distal Landing zone
Diameter:
• Similar dimensions to the proximal landing zone.
Stent-Grafting of the Thoracic Aorta 213
Length:
• Optimally, there should be 2 cm between the distal aspect of the lesion and the
celiac artery.
• The distal landing zone can be extended inferiorly by elective bypass of the celiac
and/or the other visceral vessels.
Access Vessels
The iliac and common femoral arteries should be of adequate caliber to enable
passage of the endograft delivery system.
• In practical terms, the access vessels should be at least 7 mm in diameter to allow
passage of the smaller caliber endografts.
• Wider iliac arteries are required for the widest endografts.
Equipment
Endografts
Flexibility, conformability, ease of deployment, accuracy of deployment, durabil-
ity, availability in a wide range of diameters and lengths, and low-profile delivery
systems are desirable attributes for the ideal endograft.
Several types of endograft are currently commercially available.
These include
• Talent (Medtronic)
• Valiant (Medtronic)
• Zenith TX2 (Cook, Bloomington, IN)
• Gore TAG (W.L. Gore & Associates, Flagstaff, AZ)
• Relay (Bolton Medical, Sunrise, FL )
• Evita (Jotec, Hechingen, Germany)
• Endofit (Endomed Phoenix, AZ)
The technical features of the most commonly used devices are presented in
Table 2.
Endograft Selection
The following are true about the current devices:
• No device is perfect.
214 J.-P. Beregi and M. Midulla
Ta bl e 2 Technical features of some commercially available devices (author’s personal assessments)
Device
Introducing
sheath
Introducing
system size
(F)
Available
diameter size
(mm)
Available
lengths(mm)
Bare
proximal
portion
Delayed
deployment
of more
proximal
stent
Radial
force Flexibility
MRI
compatibility
(images
artifacting)
Delivery
System
TAG (GORE) Y 20−24 26–40 20 N N + ++ Y Pull- knob
Talent
(MEDTRONIC)
N 22–27 22–46 100 Y N ++ + Y Pull-back
Valiant
(MEDTRONIC)
N 20–24 22–46 100–220
150-
Y N +++ ++ Y Pull-back
xcelerant
system
Zenith TX2 (COOK) Y 20–22 22–42 100–216
150-
Y Y ++ + N Pull-back
Relay (BOLTON) N 22–26 22–46 Y Y ++ + Y Pull-back
Stent-Grafting of the Thoracic Aorta 215
• There is no good quality scientific evidence that any one device is better than the
others.
• The majority of devices are chosen on the basis of personal preference and
experience.
• The nitinol stent-grafts are MR compatible so that the risk of irradiation can be
reduced for the follow up examinations.
• In general devices are oversized by 10–20% for aneurysms and slightly less for
acute dissection (e.g., 5–10%).
• When selecting a device diameter for use in dissections, the caliber of the aorta
just proximal to the dissection should be used. This will generally be the diameter
of the mid-aortic arch.
• In acute dissections, a device length should be chosen to cover the main entry
tear.
• In chronic dissection, devices should extend from just proximal to the entry tear
to the diaphragm.
Other Equipment Required for TEVR
Other equipment required for standard TEVR includes
• Vascular Sheaths: 6–24F
b
A 6F sheath is useful for the diagnostic catheter.
b
A 16–18F sheath is r equired for passage of a balloon for dilatation of the
endografts.
b
Some endografts, e.g., Gore TAG require placement through a sheath.
• Diagnostic catheter − 90–100 cm long pigtail/flush catheter.
• Guidewires: 260-cm long Lunderquist guidewire (Cook), or similar
• Balloons to mold the endografts after deployment, e.g., Coda (Cook), Reliant
(Medtronic).
Pre-procedure Medications
• No specific medications are required before the procedure.
Procedure
Arterial Access
Endograft Insertion
Most procedures involve device insertion through standard surgical femoral arteri-
otomies:
216 J.-P. Beregi and M. Midulla
• The procedure can be performed totally percutaneously with certain closure
devices (e.g., Prostar XL, Abbott Vasc), although this technique is subject to
quite a steep learning curve with the risk of severe hemorrhage and damage to
the access arteries.
• Patients with poor access vessels may not be suitable for TEVR. However, other
access routes may be used. For example, endograft deployment via a surgical
conduit or cut-down on to the common iliac artery, the abdominal aorta, the axil-
lary artery, the subclavian artery and the common carotid artery have all been
reported.
• The exposed artery is punctured with an arterial needle. A conventional guidewire
and catheter is advanced to the aortic arch. The conventional guidewire is
exchanged for a Lunderquist exchange guidewire which is looped in the ascend-
ing aorta.
• The endograft delivery system is advanced to the site of the lesion over the
Lunderquist guidewire under constant fluoroscopic observation.
• It is better to advance the tip of the endograft to a centimeter or so proximal to the
lesion before deployment. The device can be pulled back if required, but cannot
be advanced.
• If the patient has a dissection, care must be taken to advance the delivery catheter
up the aortic true lumen and not the false lumen.
Diagnostic Catheter
A diagnostic flush catheter is required to guide accurate placement of the endograft:
• This is most commonly placed from the contralateral femoral artery through a
percutaneous 6F sheath.
• An alternative access is the ipsilateral femoral artery (by a separate puncture) or
via an upper extremity access (usually the low brachial artery).
Angiography
• If patients have a dissection, angiography should be performed in the upper
abdomen to ensure that the catheter is in the true and not the false lumen.
• In patients with aneurysms, procedural angiography is first performed with the
endograft delivery system placed at the approximate location for deployment.
Performing aortography before this stage is unnecessary, involves unnecessary
irradiation to patient and interventionalists, and is a waste of contrast medium.
• If the lesion is close to the aortic arch, it is important to see the supra-aortic
vessels in profile. Therefore aortography should be performed in the appropriate
oblique projection. Usually LAO ranges from 30 to 75
◦
.
• Standard precautions should be observed with regard to flushing catheters placed
in the aortic arch or ascending aorta to avoid cerebral air or thromboemboli.
• Aortography should be performed using 20–30 mL contrast medium at 15–20
mL/sec.
Stent-Grafting of the Thoracic Aorta 217
Intra-procedural Medications
• Heparin: 5,000 IU administered intra-arterially, unless there is evidence of aortic
rupture.
• Broad-spectrum intravenous antibiotics are usually given to prevent endograft
sepsis.
• Drugs are administered by the anesthesiologist to reduce the blood pressure to
100 mmHg peak systolic pressure immediately prior to endograft deployment.
Deploying the Endograft
Each endograft has a different method of deployment. A description of the methods
for the different endograft types is outside the scope of this chapter.
The following points are generic for all endografts:
• Be sure to familiarize yourself with the method of deployment for the endograft
you are using before the procedure starts. Reading the instructions at the time of
deployment with the device in the aorta is poor clinical practice and increases
complications.
• If you have never used an endograft before, it is wise to see other practitioners
deploy the endograft first. This may involve visits to other hospitals.
• For your first or second deployments, it is sensible to ask an expert with the device
to attend the procedure to help you.
• For most endograft designs, check aortograms should be performed after partial
release of the endograft to ensure that the graft is being released in the desired
position.
• If more than one endograft is required to cover the length of the lesion, make
sure that there is adequate overlap between the adjacent devices to prevent future
device separation.
• Molding of the endografts is usually performed after deployment to ensure full
expansion of the endograft and to enhance the seal between adjacent devices and
between the endografts and the landing zones.
• When placing endografts in true lumens in patients with dissection, balloon mold-
ing is generally not performed because of a risk of rupture of the dissection
flap.
Endpoint
Before completion angiography can be performed, the pigtail catheter, which is
“trapped” between the endograft and the aortic wall, must be withdrawn to a level
below the endografts and readvanced through the endograft lumen again, to a level
proximal to the endografts. This procedure is performed over a standard guidewire
to prevent dislocation of the endograft by the pigtail.
Technical success is defined by a completion angiogram which
218 J.-P. Beregi and M. Midulla
a
b
c
Fig. 2 (a, b, and c) Treatment of an acute dissection with a Valiant endograft. Figure (a) shows
a dissection of the descending thoracic aorta. The main communication between the true and the
false lumen is in the upper descending aorta. After insertion and deployment of a single Valiant
endograft, the main fenestration has now been covered. A follow-up CT scan performed a week
later showed no residual false lumen perfusion in the thorax
• Shows a patent endograft (or endografts)
• Exclusion of the aneurysm sac with no endoleak
• Closure of the main thoracic fenestration between the true and the false lumen in
patients with dissection
• Patency of the supra-aortic vessels and/or the celiac artery if these vessels are
close to the lesion
Examples of TEVR in a patient with acute type B dissection and in another
patient with a ruptured aneurysm of the descending thoracic aorta are presented
in Figs. 2 and 3.
Immediate Post-procedural Care
This consists of standard recovery procedure after general or regional anesthesia.
Specific points after TEVR include
• Patients should be monitored for stroke or paraplegia.
• If there is evidence of paraplegia, a percutanous spinal drain should be placed to
reduce the pressure of the cerebrospinal fluid. This is performed by anesthesiol-
ogists.
• There is no evidence to support routine prophylactic preoperative spinal drainage
for all TEVR procedures.
Stent-Grafting of the Thoracic Aorta 219
a
b
c
Fig. 3 (a, b, and c) Treatment of a patient with a contained rupture of an aneurysm of the descend-
ing thoracic aorta. Figure (a) shows the aneurysm and a hemothorax. The patient was treated by
the emergent insertion of two overlapping Valiant endografts. The procedure was successful and
the patient was discharged 14 days later
• Some interventionalists place preoperative spinal drains in patients who have pre-
viously undergone abdominal aortic surgery or in patients in whom it is planned
to cover a long length of thoracic and abdominal aorta with endografts.
220 J.-P. Beregi and M. Midulla
Follow-Up and Post-procedure Medications
Follow-Up
• Regular follow-up by CT or MR is mandatory to monitor for complications.
• Regular plain radiographs of the endografts are also necessary to monitor
for continued integrity of the devices, i.e., disconnection and metallic strut
fracture.
• Follow-up protocols vary. Our patients undergo CT scans pre-discharge, at 3
months, at 1 year, and at annual intervals thereafter. Plain radiographs are
performed before discharge and at annual intervals.
• Specific features to look for on follow-up imaging include endoleaks, change in
aneurysm sac size, endograft disconnection, persistent perfusion or thrombosis
of the false lumen, and any new relevant findings involving the aorta or other
viscera.
Post-procedure Medications
There are no specific medications to be taken after TEVR:
• Most patients take antiplatelet therapy in the form of aspirin.
• Routine antibiotics or clopidogrel are not required
Results
The technical success of TEVR is very high and is reported as constantly above 90%
for all indications.
Apart from technical success, the outcome data tend to vary slightly with
indication.
Aneurysms
• For descending thoracic aneurysm, the EUROSTAR collaborators reported data
in 249 patients with 30-day mortality for elective TEVR of 5.3% and paraplegia
of 4%.
• Similarly, the European Talent Registry reported technical success of 98%,
in-hospital mortality in 5%, paraplegia in 1.7%, and stroke in 3.7%. Similar out-
comes have been reported for the newest generation of endografts, despite the
fact that patients in these later series had more challenging anatomy compared
with earlier series.