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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_3751_Библиотеки_им_академика_М_И_Перельмана
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descendingthoracicaorta.
■VariousdevicesarecurrentlyFDAapprovedforTEVAR,withgrowingevidencesupporting
theirsafetyandefficacy.
■Carefulpreoperativeplanningisindispensableinordertochoosethecorrectstenttypeand
minimizecomplications.
■Revascularizationanddebranchingprocedures(hybridrepair)shouldbeconsideredonan
individualizedbasis.
■Endovasculartreatmenthaslessperioperativemorbidityandmortalitythanopenrepair;
however,long-termresultsregardingthedurabilityandreliabilityofthesedevicesare
scarce.
I.Introduction
Since the preliminary reports on thoracic endovascular aortic repair (TEVAR) in 1994,1 major
advancementshavebeenachievedinthestentmaterials,sizes,conformability,grafttapering,techniques
of deployment, and the applications of this life-saving method of treatment. TEVAR has successfully
reoriented thecurrent treatment guidelines ofdescendingthoracic aortic aneurysms (DTAs) as TEVAR
permitstheintroductionofastentgraftintothedescendingorthoracoabdominalaortathroughaminimally
invasiveincision.AlthoughTEVARwasinitiallyintroducedforthetreatmentofdegenerativeaneurysmal
aorticdiseasesinnonsurgicalcandidates,TEVARisnowconsideredavalidtreatmentoptionforanarray
ofotheraorticpathologies,withtheadvantagesoflowermorbidity,avoidanceofathoracotomyincision,
and the elimination of the need for partial or total circulatory support. This chapter discusses the
endovascularrepairofaorticpathologiesafflictingthedescendingthoracicaorta.
II.AnatomicBackground
Thedescendingaortais thelongestsegmentofthethoracicaorta,beginning attheisthmusbetweenthe
originoftheleftsubclavianarteryandtheligamentumarteriosum andcoursinganteriortothevertebral
column, giving off paired thoracic arteries (T1-T12), and then traversing the aortic hiatus in the
diaphragm into the abdomen to continue as the abdominal aorta. The abdominal aorta extends
retroperitoneallytoitsbifurcationintothecommoniliacarteriesatthelevelofthefourthlumbarvertebra.
A.LandingZones
For the purpose of describing the extentof endovascular coverage,the thoracic aorta is divided into
landing zones,2 which determine the location of the stent and define the need for a concomitant
debranchingprocedure(Fig.6.1):
■Zone0:Proximaltothetakeoffoftheinnominateartery
■Zone1:Distaltotheinnominateartery,butproximaltotheoriginoftheleftcommoncarotidartery
■Zone2:Distaltotheoriginoftheleftcommoncarotidartery,butproximaltotheleftsubclavian
artery
■Zone3:≤2cmfromtheleftsubclavianarterywithoutcoveringit
■Zone4:>2cmdistaltotheleftsubclavian, butwithintheproximal halfofthedescendingaorta
(T6)
■Zone5:Startsinthedistalhalfofthedescendingthoracicaorta,butproximaltotheceliacartery
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■Zone6:Coeliacorigintothetopofthesuperiormesentericartery
■Zone7:Superiormesentericarteryorigin,suprarenalaorta
■Zone8:Coversatleastonerenalartery
■Zone9:Infrarenal
■Zone10:Commoniliac
■Zone11:Externaliliac
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FIGURE6.1 Zonesofattachment.
Reprintedwithpermissionfrom
FillingerMF,GreenbergRK,McKinseyJF,ChaikofEL.SocietyforVascularSurgeryAdHocCommitteeonTRS.Reportingstandardsforthoracic
endovascularaorticrepair(TEVAR).JVascSurg.201052:1022-1033,1033.e1015.
B.SpinalPerfusion
Thespinalcordissuppliedbybranchesofthevertebralartery:oneanteriorspinalartery(supplyingthe
anterior two-thirds of the spinal cord) andtwo posterior spinal arteries (supplyingthe posterior onethird),whichanastomose distallyatthe conus medullaris. Thethoracicaortaisdependentonradicular
contributionstotheanteriorspinalarteryviathearteryofAdamkiewicz,whichcanbefoundbetweenT9
andT12in75%ofindividuals,andothersegmental(intercostal)arteries.
3
III.IndicationsforTEVAR
TEVARwasinitiallyintroducedforthetreatmentofthoracicaorticaneurysmsinpatientswhocouldnot
tolerateopenrepair.KeystonetrialsledtoapprovalbytheUnitedStatesFoodandDrugAdministration
(FDA)in2005.4Sincethen,TEVARhasbeenatreatmentmodalityforotheraorticpathologies,suchas
aorticdissection,blunttraumaticaorticinjury,andpenetratingaorticulcers.
5,6
TEVARhasalsoexpanded
itsreachbeyondtheoriginalnonsurgicalpatientstopatientswhowouldalsobesuitableforopensurgery.
A.ThoracicAorticAneurysms
1.PatientswithlargeDTAsareatriskofdirecomplicationssuchasruptureordissection.Theriskof
complicationsincreasesasthediameterofthedescendingaortaenlarges,witha“hingepoint”at7cm.
7,8
However,bythe time theaorta reachesthis size,43% ofpatients suffer a devastatingcomplication.
9
Survival can be improved with preemptive open surgical repair of the aorta, before these critical
diametersarereached.
10,11
Althoughthereisapaucityofdatacomparingendovascularrepairtomedical
management,itisplausibletoassumethatoutcomeswouldbebetterwithendovascularrepair(ratherthan
purelymedicalmanagement)inpatientswithindicationsforopensurgicalintervention.
2.Thecurrentrecommendations forTEVARinpatientswithdegenerativeaneurysms ofthedescending
thoracic aorta include aortic size exceeding 5.5 cm, saccular aneurysms, or postoperative
pseudoaneurysms (class: Ib).10 TEVAR aims to exclude the aortic aneurysm from the circulation by
implantingamembrane-coveredstent-graftacrossthelesion,inordertopreventfurtherenlargementand
eventualaorticrupture.InDTAs,itisrecommendedthatstent-graftexceedthereferenceaorticdiameter
atthelandingzonebyatleast10%-15%(toproducea“seal”).
B.ThoracicAorticDissection
1. Repair ofdescending aortic dissection (DescAD) (type B in Stanford classification,or type III in
DeBakeyclassification)isindicatedinpatientswithcomplications,whichtypicallyoccurwithinthefirst
2weeksofdiagnosis,affectingapproximately25%ofpatients.
10–13
Thesuitablecomplicationsinclude
thefollowing:
a. End-organmalperfusion
b. Refractorypaininspiteofoptimizedmedicaltreatment(OMT)
c. Rapid expansion if the false lumen (which may be appreciated over the first several months
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followinganacutepresentation)
d. Impendingorfrankrupture
e. AneurysmaldilationinachronicDescADmeetingcriteriaforrepair
2.TEVARaimstostabilizethedissectedaortatopreventlatecomplicationsbyinducingfavorableaortic
remodeling.Obliterationoftheintimaltearbyimplantationofastent-grafthelpsredirectbloodflowinto
the truelumen(TL),thusimprovingdistal perfusion.14At least 1 or 2 cm ofdissected aortamustbe
coveredtoprovidestentfixation.Thrombosisofthefalselumen(FL)isalsopromotedbystentgrafting,
whichinducesthebeneficialprocessofaorticremodeling.
3. For uncomplicated DescAD, reports from the International Registry of Acute Aortic Dissection
(IRAD)shownobenefitofTEVARovermedicaltherapy.15ForcomplicatedacuteDescAD,TEVARis
thetreatmentofchoice.
16
4.TheINvestigationofSTEntgraftsinpatientswithtypeBAorticDissection(INSTEADtrial),
17
which
compared TEVAR+ OMTwith OMTaloneinpatients withuncomplicated typeB AD, has shownno
significantdifference in the2-year all-cause mortality, with88.0% survival at 2 years inthe TEVAR
group,versus95.6%intheOMTgroup.Five-yearfollow-up(theINSTEAD-XLtrial)wasconductedvia
a special (controversial) statistical analysis method(Landmarkanalysis).18 Analysis showed thatall-
cause mortality in the TEVAR + OMT group versus OMT-alone group was 11.1% versus 19.3%
(P=0.13),aorticdeathswere6.9%versus19.3%(P=0.04),andprogressionofthepathologyoccurred
in27%versus46.1%(P=0.04),respectively.
5.TheINSTEAD-XLtrialwasdesignedtoevaluatepatientswithmorechronicdissections(56daysin
the stent-graft group vs 75 days inthe medical managementgroup). The controversyarose inthat the
Landmarkmethoddoesnotincludeperiproceduralearlymortalityintheanalysis.Detractorspointoutthat
thechoiceofLandmarkanalysismayhaveproducedbetterapparentoutcomesthanwouldhavebeenseen
withstandardanalyticmethods.
C.OtherPathologies
TEVARcanalsobeutilizedinpatientswithbluntthoracicaorticinjuriesduetohigh-speeddeceleration,
with significantly lower perioperative morbidity and mortality compared with open repair.19 Other
lesionsinthespectrumofaorticdissection(e.g.,intramuralhematoma/penetratingaorticulcer)canalso
bemanagedwithanendovasculartechnique,soastoexcludetheaorticlesion,ortocovertheintimaltear
inany coexistentdissection.Endovascular techniques can also beutilized in cases of aortoesophageal
fistulaasatemporizingmeasuretopreventexsanguinationandallowforfluidresuscitation.
20
IV.EndograftStructure
Endovascular grafts are usuallyinserted via atransfemoral approach.Upondeployment, theendograft
self-expandstoexcludethenativediseasedaortafromthecirculationandcomesincontactwiththeaortic
wallproximallyanddistallyinatight-sealfashion(Fig.6.2).Significantvariationsingraftdesignexist.
However,allstentsarecomposedofadeliverysystem,maindevice,anddeviceextensions.
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FIGURE6.2 TheZenithAlphathoracicstentgraft.Thoracicendovasculargraftsrequireproximalanddistalseal
zonesofleast2cm.
PermissionforusegrantedbyCookMedical,Bloomington,Indiana.
A.DeliverySystem
The sizeofthe deliverysheathdepends on the diameter oftheendograft that needs tobedeployedto
provideappropriatefixation.Deliveryisusuallyaccomplishedviaafemoralapproachbydirectsurgical
cutdown. If the diameter of the femoral or iliac artery is too small to withstand the delivery system,
accesscanbeobtainedbydirectpunctureoftheiliacarteryortheaortaviaaretroperitonealincision,or
bysuturingasyntheticconduitontotheiliacartery.
B.MainDevice
Theendograftcanbestraightortaperedandmayormaynothavealongitudinalsupport.Thegraftselfexpands, but subsequent ballooning is an option. Fixation systems may include barbs or uncovered
proximalstents.
C.Extensions
These are utilized during deployment if adequate positioning of the endograft is not obtained, or if
postdeployment aortography reveals endoleaks. Proximal or distal extension devices can provide a
completeseal.
V.AvailableEndograftsforTEVAR
Multiple devices are currently FDA approved for thoracic endovascular repair from different
manufacturers(Table6.1). ThesedevicesincludetheGore TAGandCTAG(W.L. Gore & Associates,
Newark, DE), Zenith TX2 and Zenith Alpha (Cook Medical, Bloomington, IN), Valiant (Medtronic
Vascular,SantaRosa,CA),andtheRelay(BoltonMedical,Sunrise,FL).
Table6.1
SummaryofThoracicDeviceCharacteristics
Device TAG CTAG ZenithTX2 Zenith
Alpha
Valiant Relay
Manufacturer W.L.Gore&
Associates
W.L.Gore
&
Associates
CookMedical Cook
Medical
MedtronicVascular BoltonMedical
Device
structure
Tube-shapedstentgraftlinedwith
ePTFE/FEP,and
supportedbya
nitinolexoskeleton
Similar
designtothe
TAG,but
more
conformable
Dacrongraft
sewntoa
stainlesssteel
stent
Similar
toTX2
Self-expandingtubewith
nitinolscaffoldingsewnto
theoutsideofthegraft
material.Lacksa
longitudinalsupportbar,for
moreflexibility
Self-expandingnitinol
stent,suturedtoa
polyesterfabricgraft.
Longitudinalsupport
achievedviaanitinolwire
Proximaland
distalends
Flaredexposed
stentapices
Similarto
theTAG
device
Externalbarbs
proximallyand
distally.
Extension
BMSis
available
Similar
toTX2
Proximalendisbarestent
witheightshorterbare
stents.Distalstentgraft
withaclosedweb
configuration
Twoversions,theRelay
withproximalbarestent,
andtheRelay-NBS,
withoutbarestent.One
distalconfigurationis
available
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Diameter
(mm)
26-45 21-45 28-42 18-34 24-46 22-46
Length(cm) 10-20 10-20 12-21.6 10.5-16 Upto22.7 10-25
Delivery
system
20-24Fsheath Sheathless
delivery
system
20-22F
delivery
sheath
16-20F
sheath
Xcelerantdeliverysystem 20-26Fdeliverysheath
BMS,baremetalstent;ePTFE,polytetrafluorethylene;FEP,fluorinatedethylenepropylene.
A.TAGandCTAG
1. The TAG device (W.L. Gore & Associates) is a flexible tube-shaped stent-graft, lined with
polytetrafluorethylene(ePTFE)“Teflon”andcoveredwithanadditionallayerofTeflonandfluorinated
ethylene propylene (FEP), to further reduce friction and the occurrence of endoleaks (Fig.6.3). It is
supported through itsentire lengthwithanitinol exoskeleton. Theproximal endofthegraftconsistsof
exposedstentapices,whereasthedistalendremainsinlinewiththegraftmaterial.Radiopaquebandsare
present at each end to facilitate placement under fluoroscopy. These flared endings are intended to
improvesealingandattachmentofthegrafttotheaorticwall.
22
FIGURE6.3 Original(top)andredesigned(bottom)GORETAGdevices.
Reprintedwithpermissionfrom
MakarounMS,DillavouED,KeeST,etal.Endovasculartreatmentofthoracicaorticaneurysms:resultsofthephaseIImulticentertrialoftheGORE
TAGthoracicendoprosthesis.JVascSurg.2005;41:1-9.
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2. A next-generation device, the Conformable TAG (CTAG) shares a similar design but offers more
conformabilitytoaccommodatemoreacuteangles,oftenfoundintheaorticarch.Thisisachievedthrough
modificationofthematerialandtheattachmentoftheexoskeletontothegraft.
3.TAGdeviceisavailableindiametersfrom26to45mmin10, 15,and20cmlengths.Thedelivery
sheathrangesfrom20to24Frenchindiameterdependingonthedevicesize.CTAGoffersawiderrange
ofdiameters(21-45mm),23withasheathlessdeliverysystem.Theendoprosthesisisconstrainedinsidea
deploymentsleeve and mounted onto the leading end of the deliverycatheter. Pulling the deployment
knob,whichisattachedtothedeploymentlinesystem,unlacesthesleeveandallowstheself-expanding
endoprosthesistodeploy. Thisallows the CTAGtoconformtosmallerandmore taperedaortasandto
provideasolutionfornonaneurysmalaorticpathologiessuchasbluntaorticinjury.
22
4.ThesafetyandefficacyoftheTAGendografthavebeendemonstrated.Althoughtheinitialresultswith
the TAG device were disappointing, and the trial was stopped owing to complications,24 further
modificationsofthedevicehaveproventobeefficacious.Inamulticenterstudycomparingendovascular
DTArepairusingtheTAGdevicewithopenrepair,aorta-specificsurvivalwassignificantlybetterinthe
endovasculargroupat5years(96%vs88%,P=0.24), andmajoradverse eventswerereducedat30
days(21%vs71%,P<0.001)andat1year(42%vs77%.P<0.001).
4,25
5.TheAorticDissectionStent-graftORBestMedicalTreatment(ADSORB)trial,comparingoutcomes
ofOMTonlyversusOMTandtheGoreTAGdevice,inpatientswithuncomplicatedtypeBdissection,
demonstratedthesafetyofthedevice.26Thefalselumen(FL)decreasedinsizeintheOMT+TAGgroup
(P<0.001),whereasintheOMTgroupitincreased.Thetruelumen(TL)increasedintheOMT+TAG
(P<0.001),whereasintheOMTgroupitremainedunchanged.Theoveralltransversediameterwasthe
same at the beginningandafter1 year intheOMTgroup(42.1 mm),but in theOMT + TAGgroup it
decreased(38.8mm;P=0.062).RemodelingwiththrombosisoftheFL,andreductionofitsdiameteris
inducedbythestentgraft;howeverlong-termresultsarestillneeded.
6.CriticismtotheADSORBstudyconcernedthedefinitionofFLthrombosis,whichwasnotthesamein
theOMTplusTEVARandOMTonlygroups.ForpatientstreatedwithOMTplusTEVAR,theFLwas
considered thrombosed aslong asnoflowwas visualizedinthefalse lumenparallel to theendograft,
excludingthedistal2cm,whereasintheOMTgroup,thefalselumenwasonlyconsideredthrombosedif
there was noflowinanysegmentofthe thoracicaorta,a difference that wouldappear substantially to
favortheTEVARgroup.
27
7.ThesafetyandefficacyoftheCTAGdevicewasevaluatedinanonrandomizedstudywith51patients
sufferingfrombluntaorticinjury,28with nooperativemortalityandnomajordevice events.Thirty-day
mortality,unrelatedtodevice,was7.8%.
B.ZenithTX2andZenithAlpha
1.Zenith TX2endograft(Cook Medical)andZenithAlpha(new generation,low profilestents
29
)are
two-piece systems, proximal and distal. They are constructed offull-thickness wovenpolyester fabric
(i.e., Dacron), sewn to self-expanding special stainless steel stents, with braided polyester and
monofilament polypropylene suture. The graft body stents and the distal sealing stent are made from
superelasticelectropolishednitinolwire30(Fig.6.2).Activefixationattheproximalanddistal endsis
achievedviaexternalbarbsforeachcomponent.Anextensionbaremetalstentisavailable,whichcanbe
usedtodistallyfixatethegraftovertheoriginsofthevisceralarteries.AmodificationoftheTX2device
(Pro-form) is intendedto improve conformabilityandapposition of thegraft in the aortic archduring
proximal descending thoracic aortic deployments, in order to minimize the risk of graft folding and
collapse.
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2. Proximal anddistal Zenith TX2 device components are available in diameters ranging from 28 to
42mm,andthecomponentsrangeinlengthfrom12to21.6cm.Deliverysheathisa20or22French.
29
ZenithAlphaisavailableindiametersfrom18to34mm,withcomponentlengthsfrom10.5to16cm.
29
Thedevicesaredeliveredthrougha16-20Frenchsheathdependingonthediameterofthedevice.Both
devicesareself-expanding;however,subsequentballooningisanoptionwhenneeded.
3. Thesafety and efficacyof theZenith TX2endograftwere evaluatedin a multicenter study of 230
patientswithDTAs,whoweretreatedwithTEVAR(n=160)oropenrepair(n=70).30Perioperative
morbidity was significantly lower for endovascular repair (composite index 1.3 vs 2.9, P < 0.01).
Endovascular repair was also associated with fewer cardiovascular and pulmonary adverse events;
however,incidenceofneurologiceventswasnotsignificantlydifferent.At12months,aneurysmgrowth
wasidentifiedin7.1%,endoleakin3.9%,andmigration(>10mm)in2.8%oftheendovascularpatients.
4. The Zenith TX2 dissection system shares a similar design, and its efficacy was evaluated in the
STABLE trial, in 40 patients with complicated DescAD, defined by branch vessel malperfusion,
impendingrupture,aorticdiameter≥40mm,rapidaorticexpansion,andpersistentpainorhypertension
despitemaximummedicaltherapy.32Sevencombinationsofstentgraftsanddissectionstentswereused,
and all devices were successfully deployed and patent. One-year survival rate was 90%. Morbidity
occurring within 30 days includedstroke(7.5%),transient ischemicattack (2.5%), paraplegia (2.5%),
retrogradedissection(5%),andrenalfailure(12.5%).Favorableaorticremodelingwasobservedduring
thecourseoffollow-up,indicatedbyanincreaseintheTLsize,andaconcomitantdecreaseintheFLsize
along the dissected aorta, with completely thrombosed thoracic FL observed in 31% of patients at
12months.
C.ValiantThoracicStent-GraftSystem
1. The Valiant endograft (Medtronic Vascular) is a modified version of the earlier Talent endograft
system(withdrawnbymanufacturer).Itiscomposedofaself-expandingtube.Thenitinolscaffoldingof
thestentgraftiscomposedofaseriesofserpentinefive-peakedspringsstackedinatubularconfiguration.
Thescaffoldinginthisdeviceissewntotheoutsideofthegraftmaterial(nottheinside,aswiththeTalent
device)(Fig.6.4).Valiant device lacksthelongitudinalsupportbar ofthe earlier device, which gives
moreflexibility.Thedevicehasamodifiedproximalbarestentwitheightshorterbarestentsproximally.
Adistalstentgraftcomponenthasaclosedwebconfigurationattheproximalend(nobarespring)anda
closedweboraneight-peakbare-springconfigurationatthedistalstentend.
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