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valve replacement.Generally,surgery oftheascendingaortarequires arrestingoftheheartduring
theaorticreconstructionandinstitutionofartificialbloodcirculationviatheuseofcardiopulmonary
bypass. One of the biggest challenges in the surgical approach to ascending aortic aneurysms is
interventionon the aortic arch. When the aortic archis intervened upon,blood flow to thehead
vessels generally must be interrupted (requiring methods for cerebral protection, such as deep
hypothermic circulatory arrest [DHCA]) or substituted artificially. Currently, three methods for
cerebral protectionare used independently or concurrently: DHCA, antegrade cerebral perfusion
(ACP),andretrogradecerebralperfusion(RCP).Furthermore,threeapproachesfortheaorticarch
replacementaregenerallyappliedaccordingtoanatomicindications.
14
i. Proximalhemiarchresection:Inthisprocedure,thearchvesselsareleftintactwhilejustthe
undersurface ofthe aortic archis replaced. This suffices for many ascendinganeurysmsthat
tapergraduallyastheyreachthearchzone.
ii. Complete archresection: In these procedures, the entire aortic arch is replaced. Cerebral
bloodflow is reconstitutedeither byreattaching an“island”ofaortic wallcarryingthegreat
vessels(Carrelpatch)orbygraftstotheheadvesselsthemselves.
iii. Elephanttrunkprocedure:Thisprocedureisusediftheaneurysmextendsintothedescending
aorta,requiringatwo-stageapproach.Duringthefirststageoneaccomplishesplacementofan
“elephanttrunk”sewntotheendoftheaorticarchwiththedistalendofthegrafthangingfreely
inthedescendingaorta.Duringthesecondstage,about4weekslater,thedescendinganeurysm
isresectedandthedistalendoftheelephanttrunkisattachedtothenormalaortabelow.
b. Currently,opensurgeryoftheascendingaortaandaorticarchhasproventobeexceptionallysafe,
with a mortality of 2.1% at 30 days; including a 1.5% mortality for elective cases and a 6.3%
mortalityforemergentcases.12Therefore,opensurgicalrepairisthecurrentstandardoftreatment
forpatientswithascending aorticpathology.Furthermore,severalotherpathologies suchasaortic
pseudoaneurysm,PAU,IMH,andaruptureoftheascendingaortacanbeeffectivelyapproachedwith
an open surgical repair, thus eliminating their inherent risk of catastrophic events. Endovascular
repair is reported intheliteratureless frequentlyfor these pathologies than foraortic dissection;
however,thefocallocalizationoftheselesionsintheaortamakesthemamenabletotheplacementof
anendograft.
8,10
5.AorticPseudoaneurysm:
Atrueaneurysm,aspreviouslydescribed,isaweakeningofthethreelayersoftheaorticwall.However,
apseudoaneurysmisalossofcontinuitywithbloodaccumulationthatiscontainedbytheadventitiaofthe
aorta or surrounding scar tissue.This can beseen atsurgical anastomotic sites, such as proximal and
distalgraftanastomosesandcoronaryreimplantationsites.Pseudoaneurysmsalsodevelopaftercomplex
aorticvalvesurgerywithrootenlargingproceduresorinsettingsofendocarditisandtissuedestruction.
Because of pressurizedflow into the sac, pseudoaneurysms pose an increased risk of ruptureinto the
mediastinumandpleuralspacesthatisveryoftenfatal.
27
6.PenetratingAorticUlcer:
PAUis characterizedbyaregionoftheaortawithatherosclerotic changesandanulcer-likeprojection
appearance(seeFig.5B.4).Theintimaistransgressedandthelesionprogressesthroughtheaorticwall;
also, it mayor maynot be associatedwith an overlying thrombus. PAU canbe an entrypoint forthe
developmentofdissectionandmaybeassociatedwiththedevelopmentofahematomawithinthemedia
thatleadstodissectionorevenrupture.
28,29
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FIGURE5B.4 Variantformsofaorticdissection:typicalaorticdissection,penetratingaorticulcer,andintramural
hematoma(IMH).NotetheconcentricnatureofthehematomainIMH.
Reproducedwithpermissionfrom
ElefteriadesJA.Thoracicaorticaneurysm:readingtheenemy’splaybook.CurrProblCardiol.2008;33(5):203-277.
7.IntramuralHematoma:
IMHisavariantofaorticdissection(seeFig.5B.4);thereisaninvolvementofthemediallayerofthe
aortic wall in the absence of an intimal tear; however, it can be associated with the presence of
microtears and the development of a hematoma. IMH is hypothesized to occur after the spontaneous
ruptureofthevasa-vasorumordisruptionofthemediainducedbyaPAU.IMHhasathinneroutermedia
thatincreasestheriskofruptureincomparisonwithpatientswithaorticdissection.
28,30
III.EndovascularManagementoftheAscendingAortaand
AorticArch
A.ImplementationofTechniques
Thesuccessfulimplementationofendovasculartechniquesintheabdominalaortahasrenderedtheopen
procedureasasecond-lineoftreatmentinpatientswithabdominalaorticdiseases.Endovascularrepair
instead,becamethegoldstandardforthemanagementofacuteandelectiveabdominalaorticconditions.
Therefore,enthusiasmexpandedtothethoracicaorticsegmentsforthemanagementofconditionssuchas
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aneurysms, dissections, and PAUs with the intention of reducing complications such as early death,
paraplegia, renal insufficiency, and cardiac events associated with the open surgical repair.8 The
proximal aortic segments are the ultimate frontier for endovascular techniques. However, the closer
endovasculartherapygetstotheaorticvalve,themorecomplexanddangerousitbecomes.Anatomical
and physiological complexities complicate the adequate deployment and application of endovascular
devices. Additionally, there is a lackofascendingaorta–specific devices thatare necessary tofitthe
anatomyandhemodynamicforcesthatareexperiencedintheproximalportionoftheaorta.
8
B.AnatomicandHemodynamicChallenges
1. Theanatomyoftheascendingaortaand theaortic archposes achallengeforthe implementationof
endovascular techniques. The proximity of the aortic valve and coronary ostia below the sinotubular
junction can lead to aortic insufficiency or myocardial infarction following stent deployment in so
proximalaposition.Also,thepresenceoftheheadvessels(innominateartery,leftcommoncarotidartery,
andleftsubclavianartery)placesthepatientatriskofcerebrovascularaccidentifthereisadeployment
ormigrationbeyondthepointoforiginoftheinnominateartery.8Thus,theeffectiveareaofintervention
fortheascendingaortaislimitedtothezoneabovethesinotubularjunctiontotheoriginoftheinnominate
artery,generallyrepresentingalengthof5-7cm.31Anadditionalparameterthataffectstheproperuseof
endovasculartechniquesisthe largerdiameter ofthe ascendingaorta,on average1cm largerthanthe
descendingaorta;this limits the rangeof stents thatcanbe borrowed fromthosecommonly employed
during TEVAR.
8,10,32
Furthermore, because of the short segment of the ascending aorta, achieving the
generallyrecommended20mmlandingzonecanbechallenging;hence,somereportsrecommendparing
thelandingzonetoanewlowerminimumof10mmtoavoidobstructingthecoronaryostiaortheaortic
valve,proximally,andtheinnominatearterydistally.
8,33
2. The hemodynamic forces and the pronounced diameter changes during the cardiac cycle in the
ascendingaortacanhindertheprecisedeploymentofstents.Thehighersystolicflowincomparisonwith
thedescendingaortacanlead tomigrationofthe stent whilebeingdeployed,aphenomenon known as
“windsock.”34 Consequently, the use of special technical maneuvers may be necessary; these include
rapidventricularpacingto180bpm,adenosineinjectionfortransientcardiacarrest,venacavaocclusion,
or medicationssuchas nitrates—all applied todecrease afterload, blood pressure, and cardiac output
duringendograftplacement.
8,10,33
Thegreatestchangesindiametersduringthecardiaccyclereach5mm
justdistaltothecoronaryarteries,representingameanchangeof17%,andalso5mmnotedproximalto
the innominate artery, a change of 14 %. To plan optimally, ECG-gated computed tomographic
angiography(CTA)canspecificallyevaluatethepulsatilityoftheascendingaortaforbettersizing.
7
C.IndicationsandPatientSelection
1. Patientswith advancedageor multiplemedical comorbiditiesandthosewhoareotherwiseunfitto
undergo surgeryoftenhavepooroutcomes withexclusivemedicalmanagementforadvancedascending
aortic pathology. For instance, patients with type A aortic dissection have an in-hospital mortality
approaching60%whentreatedmedically.33Infact,anoverallof28%ofpatientswithascendingaortic
pathology are deemed to be unsuitable for an open surgical procedure.33 When a patient is deemed
inoperable,theendovascularapproachtakesitsrelevance.Promisingresultsofendovascularstentingin
caseseriesandcasereportssupportuseofthisapproachforfocallesionslocatedintheareaabovethe
sinotubular junction but below the origin of the innominate artery.
8,10
The minimally invasive
endovascular approach has been used for acute and chronic type A aortic dissections (48%), aortic
pseudoaneurysms(27.7%),ascendingaorticaneurysm(5.1%),PAU(4.2%),IMH(2.5%),andruptureof
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theascendingaorta(2.5%).
8,10
Despitetheuseoftheendovasculartechniquealmostexclusivelyinhigh-
riskpatients,hightechnicalsuccess(96%)andlowconversionratestoopensurgery(0.7%)havebeen
reported.
35
2. The anatomical likelihood of suitability of an endovascular approach for the ascending aorta in
patientswithtypeAaorticdissectionisbasedonseveralspecificanatomicvariables:absenceofaortic
valvularpathology(aorticregurgitation), adequateaorticlengthforsealingzones,favorablelocationof
coronary ostia (to avoid occlusion). More specifically, the following prerequisites are suggested to
chooseasubsetofpatientsmostlikelytobenefitfromanendovascularapproach:
a. Presenceofproximalanddistallandingzoneswithalength>10mm,
b. Nodifferenceindiameters(<10%)betweenproximalanddistallandingzones,
c. Trueaorticlumendiameter≤38mm,
d. Totalaorticdiameter>16mmand<46mm,
e. Absenceofcoronaryarterybypassoriginatingfromtheascendingaorta,
f. Absenceofcalcificationorthromboticmaterialinascendingorneighboringaorticzones,
g. Intimaltear>10mmabovethesinotubularjunction,
h. Intimaltear>5mmbelowtheinnominateartery,
i. Absenceofgrade3or4aorticregurgitation,and
j. Diameterofthecommonandexternaliliacarteries>7mm.
7,34
3.Endovascular repair oftheascending aortaiscontraindicatedinthepresenceofsevereaorticvalve
regurgitation, ifthe type A aortic dissectioninvolves the aortic rootproper, and (inthe mindofmost
authorities)patientswithconnectivetissuedisease(Marfan’s,Loeys-Dietz,Ehlers-Danlos).However,in
patients with connective tissue pathologies, endovascular therapy can be utilized as a bridge until a
definitiveopensurgicalapproachcanbedone,deferringtheacutenessoftheprocesstoamoresubacute
andcontrolledsituation.
7
D.DevicesfortheAscendingAorta
1.Devices:
The appeal of endovascular therapyforthe ascendingaorta is tempered bythelackof specific aortic
devices.Endograftsappliedfortheascendingaortausuallycorrespondtodesignsintendedfortreatment
of descending thoracic aortic (TEVAR) and abdominal aortic pathologies.31 However, some
investigational devices have been designed specifically for the ascending aorta, including the Zenith
Ascend(CookMedical,Bjaeverskov,Denmark)andtheValiantPS-IDEdevice(Medtronic,Minneapolis,
MN).
a. ZenithAscendDevice(CookMedical,Bjaeverskov,Denmark):TheZenithAscendstentisan
investigationaldevicetailoredtotheascendingaortaforthetreatmentoftypeAaorticdissectionand
aneurysmaldisease.IthasfirstbeenusedinEurope,withafewcasesreportedintheUnitedStates
undercompassionateusethroughaninvestigationaldeviceexemptionprotocol.34TheAscend
deviceprovidesalowerprofile,withpolyesterfabricandnitinolstents,withashorterandflexible
tipintendedtodecreaseventricularandvalvetrauma.Additionalsupportandfabricappositionare
achievedwithproximalanddistalbare-metalfixationstents,whichdecreasetheriskof
compromisingthecoronaryorinnominatearteries.
32,34
Ascendisrecommendedforuseinpatients
withthefollowinganatomiccriteria:minimum10mmlandingzonesdistaltotheoriginofthe
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coronaryarteriesandproximaltotheoriginoftheinnominateartery,andanaorticdiameterno
greaterthan40mmandnolessthan24mm.
34,36
b. ValiantPS-IDE(Medtronic,Minneapolis,MN):TheValiantPS-IDEendograftisamodificationof
theValiantThoracicstentgraftusedinTEVAR.Ithasbeenmodifiedtotreatascendingaortic
pathologies,adjustingtheoriginalconfigurationtofittheshortersegmentandthewiderdiameterof
theascendingaorta.Itwasusedinaprospectivestudytodeterminethefeasibilityofsuccessful
implantation.Twoconfigurationswereproposed:aproximalFreeFlotaperwithadistalclosed-web
andaproximalclosed-webdesignwithbarespringsdistally.Thedeliverysystemwasidenticalto
theValiantCaptiva,withanontipcapturedeviceusedfortheproximalclosed-webdesignandatip
capturesystemfortheFreeFloconfiguration.Itwasconfiguredtobeusedinpatientswithatleast
10mmoflandingzonesproximallyanddistallytothediseasedarea,anascendingaorticdiameter
between28mmand44mm,andhigh-risksurgicalcandidateswithanAmericanSocietyof
Anesthesiology(ASA)scoreof4.
32
2.Table5B.5laysoutthedifferentendografts(bothascendingspecificandborrowedfromTEVAR)that
havebeenappliedtotheendovascularmanagementoftheascendingaorta.
8,10
TABLE5B.5
DifferentTypesofStentsUsedfortheEndovascularTreatmentoftheAscendingAortaa.
8,10
Device/StentGraft
ZenithTX2Pro-Formendograft(CookMedical,Bloomington,IN)
ThoracicTAG(GoreMedical,Flagstaff,AZ)
Talentthoracicstentgraft(Medtronic,Minneapolis,MN)
Valiantstentgraft(Medtronic,Minneapolis,MN)
a
Zenithascendingdissectiondevice(CookMedical,Bjaeverskov,Denmark)
a
Sealthoracicstentgraft(S&GBiotech)
Najutathoracicstentgraftsystem(Kawasumi)
Custom-madegrafts
Excluderabdominalcuff(GoreMedical,Flagstaff,AZ)
Endurantaorticcuff(Medtronic,Minneapolis,MN)
RelayNBSthoracicstentgraft(BoltonMedical,Sunrise,FL)
Zenithaorticcuffextender(CookMedical,Bloomington,IN)
a
StentsSpecificallyDesignedfortheAscendingAorta
BAV,bicuspidaorticvalveaneurysm;TAA,thoracicaorticaneurysm;TEE,transesophageal
echocardiography.
E.DeploymentofEndografts
1.Whenapatientisdeemedhighriskforopensurgeryandanendovascularapproachisconsidered,not
only the anatomic andhemodynamic profiles may pose a challenge for endograft deployment but also
anatomicvariablesaffectingvascularaccesstotheascendingaorta.Normally,withexperienceacquired
in transcatheter aortic valve replacement (TAVR), the transfemoral approach is chosen, provided that
thereisadequatediameteroftheiliofemoralvesselstoaccommodatethedeliverysheaths.7However,the
longdistancetothesinotubularjunction,comparedwiththerelativelyshortlengthrequiredforabdominal
andthethoracic devices, posesa technicalchallenge.Also, longandrigidnosecones present a riskof
ventricular perforation and aortic valve leaflet damage. Therefore, alternative access approaches that
allow a more straight and direct route to the ascending aorta have been utilized. Delivery has been
accomplished through the right and left carotid artery, right and left axillary artery, right and left
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subclavianartery,andiliacartery. Transseptalandtransapicalapproacheshavealsobeendescribedin
theliterature.
32
2.Thetransapicalapproachtriestosolvetheaforementionedproblems,eliminatingtheneedforlongand
stiffnosecones,andthusminimizingriskofassociatedcomplications.Withtheshorterdistancefromthe
LV apextothe ascendingaorta,operatorcontrolduringdeploymentisimproved.Whencombinedwith
maneuverstodecreasethecardiacoutputtransiently,theapicalapproachleadstoamorepreciselanding
ofthedevice.Additionally,withamorecontrolledtechniquefordeploymentofthegraft,abettercoaxial
placementcanbeachievedtoreducethedevelopmentoftypeIendoleaks.Oneoftheadvantagesofthis
techniqueisthecertaintyofdeploymentinthetruelumeninpatientswithtypeAdissectionachievedby
accessingtheascendingaortathroughanondissectedplane(viatheleftventricle).
32
F.PerioperativeImagingandTesting
1.Forthesuccessfuldeploymentofanendovasculardeviceintheascendingaorta,especiallythorough
preoperative planning is required. First,preoperative imaging with gated contrast enhanced computed
tomography (CT) or noncontrast time-of-flight magnetic resonance imaging (MRI) provides an
understanding of the aortic anatomy. Essential information includes aortic size and the presence of
atheroscleroticplaquesandPAUs.Furthermore,preciseimagingpermitsevaluationoftheproximaland
distal landingzones, sizeandangulationofaccess vessels, and the presenceandlocationofvitalside
branches. Additionally, for interventions that cover aortic branches, fusion images integrating
preoperativeCTAorMRAwithintraoperativefluoroscopyprovidepreciseintraoperativeroadmapsfor
thesurgeon.
7
2. Transesophageal echocardiography (TEE)alsoplays acritical role. Inthepreoperative stage, TEE
allowsforbettervisualizationofaorticvalvefunction.Intraoperatively,TEEguidestheidealselectionof
thetransapicalaccesssiteandconfirmsthepositionoftheguidewireinthetruelumen.Furthermore,TEE
helpstodetectanycomplicationafterstentdeployment,suchasiatrogenicaorticvalveregurgitationand
regionalwallmotionabnormalitiesduetoobstructionofthecoronaryostia.
7
3.Intraoperatively,neurologicmonitoringcanbeusedtoconfirmtheintegrityofbloodflowthroughthe
supra-aortic arch vessels and adequate cerebral perfusion. For instance, transcutaneous near-infrared
spectroscopy and transcranial cerebral oximetry can provide real-time information about cerebral
perfusionandoxygenation.Additionally,transcranialDopplerofintracranialvesselscandetectchanges
inblood flowandmicroemboli,whichcaninformthe surgicalteamofpartialortotalocclusionofthe
archvessels,compromisingcerebralbloodflow,ordistalembolization.
7
4. Finally, for direct visualization of the endolumninal surface, intravascular ultrasound (IVUS) is a
valuable resource, allowing measurement of the luminal diameter and precise determination of the
position of branch vessels. Also, IVUS permits the localization of plaques or thrombi and enhances
selection and achievement of landingzones.In type A aortic dissection,IVUScan beusedreliablyto
identify the true lumen (differentiating from the false). IVUS also can confirm appropriate graft
deploymentandruleoutanyendoleaks.
7
G.Complications
Mostofthecomplicationsseenwithendovascularmanagementoftheascendingaortaarenovelevento
thespecialist;however,mostofthemareexpectedbecauseoftheanatomicsingularitiesofthissegmentof
aorta.The most commoncomplicationsreported in theliterature areas follows. Perforationoftheleft
ventricleand/orformationofaleftventricularaneurysmmaybeseenwhenarigiddeliverysystemthat
must pass through the aortic valve is used. In the same setting, damage to the aortic leaflets is also
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plausible. Injury anddissectionof the aortic root and occlusionofthe coronaryarteries withensuing
myocardialinfarctioncanbeencounteredwhenthedeviceispositionedclosetothesinotubularjunction,
becauseoftheexertionofstrongradialforces toenhanceproximalfixationintheascending aorta.
32,37
Neurologic complications, such as ischemic stroke, canoccur secondary to aortic arch branch vessel
occlusion. Furthermore, particulate and/or air embolism may be seen following excessive wire and
cathetermanipulationinadiseased,atheroscleroticaorticarch.Also describedaredeploymentfailure,
developmentofendoleaks,stentmigration,needforreintervention,andconversiontoopensurgery.
8
IV.EndovascularTherapyoftheAorticArch
A.Challenges
Theaorticarchtogetherwiththeascending aortaisamongthemostchallengingareasforendovascular
therapy. The curvature of the aortic arch, the high blood flow in the area, and the presence of vital
branches thatsupply theupperbody(includingthebrain) makeany approachto thissegmentproneto
devastatingcomplications.
38
B.ApproachesandMisconceptions
1. Normally, conventional open surgical treatment for arch pathologyinvolves a sternotomy incision,
cardiopulmonary bypass,anda circulatory arrestwithdeep hypothermiawithor without ACP orRCP.
Despitepersistentmisconceptionstothecontrary, surgical advanceshaverenderedelective aorticarch
surgeryremarkablysafe;reportedpostoperativemortalityandpermanentneurologicdeficitare2.9%and
2.2%,respectively.
12
2.Recentadvancesinendovascularmaterialsandtechniquespermittheapplicationofendovascularand
combined endovascular/open (hybrid) approaches for managementofthe aortic arch, withthe goal of
reducingcomplicationsofopenandstagedprocedures.
38
3.Despiteendovascularadvancesinthemanagementoftheaorticarch,therisksofparaplegia,endoleak,
stroke, and retrograde type A dissection remain. Embolism to the cerebral circulation, especially for
patientswithhighlyatheromatousaorticarches,isreportedinupto15%ofpatientsfollowinghybridarch
repairandaccountsforthemajorityofstrokes.Paraplegia,duetospinalcordhypoperfusion,manifests
with rates about 6 %. The paraplegia risk increases with the length of aortic coverage; andprevious
infrarenal aortic surgery also increases the risk.39 Retrograde dissection is an extremely serious
complicationencounteredinpatientstreatedfortypeBaorticdissection.Retrogradedissectionseemsto
bemorecommonwhenthestentgraftsareoversizedmorethan10%.Ratesofretrogradedissectionfrom
2%to6.5%followinghybridarchrepairhavebeendescribed.TypeIaendoleakisseenin6%ofaortic
archinterventions,withreinterventionratesof18%at1year,21%at2years,and36%at5years.
39
C.AorticArchLandingZones
1.Forplacementofanendograftintheaorticarch,thestentsrequireaminimumof15mmofalanding
zone proximally and distally. However, when the aortic arch is highly angulated, the landing zone
requiredincreasesto20mm.
2.
Additionally,idealsealingzoneparametersfortheaorticarchincludeadiameteroftheaortasmallerthan
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40mm,alengthofdisease-freeaortagreaterthan20mm,andanangulationlessthan60°.39Ishimaruand
colleagues40establishedfiveaorticarchzonesthatareusedaslandinglandmarksfortheendovascular
deploymentofstents.
a. Zone0istheareaproximaltotheinnominatearteryinvolvingitsoriginandtheascendingaorta.
b. Zone1involvestheoriginofthecommoncarotidartery.
c. Zone2involvestheoriginofthesubclavianartery.
d. Zone3isbetweentheleftsubclavianarteryand2cmdistaltoit.
e. Zone4includestheremainderofthethoracicaortamorethan2cmdistaltotheleftsubclavian
artery(Fig.5B.5).
39,41
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FIGURE5B.5 Schematicrepresentationoftheaorticzonesforproperlandingofendovascularstents.
Reprintedwithpermissionfrom
FillingerMF,GreenbergRK,McKinseyJF,ChaikofEL;SocietyforVascularSurgeryAdHocCommitteeonTRS.Report ingstandardsfor
thoracicendovascularaorticrep air(TEVAR).JVascSurg.2010;52:1022-1033,1033.e1015.
V.TotalEndovascularTechniquefortheAorticArch
Whenapproachingtheaorticarch,diversetechniquesfromhybridtofullyendovascularmethodscanbe
used.Thetotalendovascularapproachincludestheparallelstenttechnique,useofendovascularbranched
endografts,andinsitufenestration.
38
A.TheParallelStentTechnique
1.Alsocalledsnorkelorchimneytechnique,theparallelstenttechniqueisusedtomaintainbloodflow
inthevitalbrancheswithinthesealingzonesoftheendovascularstentwithouttheneedforfenestratedor
branchedgrafts.Inthistechnique,acoveredstentisdeployedintovitalarchbranchesparalleltothemain
aorticgraft.
2.Theaorticstentisprolongedbeyondtheoriginoftheaorticbranches,andtheparallelgraftworksasa
functionalarmofthestentgraft.Theprimarydifficultywiththechimneytechniqueisthedevelopmentof
typeIaendoleaksduetotheinsufficientappositionofthemainbodyofthestenttotheaorticwall.The
“gutters”aroundtheparallelgraftencourageendoleakflow.
3.Theparallelgrafttechniquehasbeenreportedtohaveanoperativesuccessof99%,aperioperative
mortalityof4.5%,andastrokerateof4%.Thehighrateofstrokeisduetoembolifrommanipulationof
theaorticbranches.
39,42,43
4. Nevertheless, the snorkel or chimney graft technique is an option for emergent or urgent cases in
patientswhoarenotsurgicalcandidates,or asabailoutprocedureinunplanned coverageoftheaortic
branches.
39
B.BranchedEndografts
1.Branchedendograftsareindicatedwhenthereisaninsufficientareaforproximalsealingdistaltothe
leftsubclavianartery(zone 3 and zone 4);therefore,proximalcoverageinvolvingthe vitalaortic arch
branches is required (zone 0tozone 3).Branched endografts maintainthebenefits ofanendovascular
techniquewhileavoidingmalperfusiontotheaorticbranches.44Branchedendograftshavebeenavailable
outside the United States under individual manufacturer-sponsored custom programs for many years.
However,intheUnitedStatesbranchedendograftshavebeenemployedinafewselectedsitesundera
FDAinvestigationaldeviceexemption,mostlyasinvestigationaldevices.
44
2.Severalbranchedendograftsarecurrentlyunderinvestigation(Table5B.6).
TABLE5B.6
CurrentEndovascularAorticArchstentGrafts
39
Manufacturer Scallop Fenestration Branch ProximalLandingZone
BoltonMe dical Yes Yes Yes.Singleordouble 0
CookZe nith Yes Yes Yes.Singleordouble 0
GoreTAG No No Yes.Single 0
Me dtronic No No Yes.Single 2
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