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C.ChapterOutline
This chapter aims to provide a framework and contextual understanding of stents by discussing the
technicalandclinical performanceofdifferentstentsusedinthelowerextremity.The useofstents for
othervascularterritoriesincludingvenousinterventionwillbecoveredintheirindividualchapters.
II.Bare-MetalBalloon-ExpandableStents
A.GeneralPrinciples
Inlowerextremityarterialstenting,bare-metalballoon-expandablestentsareprimarilyusedintheiliac
territory,giventhelower degreeofstress andtorsionalmovementtowhichtheiliacarteryisexposed.
Balloon-expandable stents should not be used in areas where repeated flexing of the artery occurs.
Balloon-expandablestents areconstructedfrom stainless steelor cobaltchromiumandingeneral have
greater radial strength and radiopacity but poorer flexibility and trackability compared with selfexpandingstents.Giventhemechanismofdeployment,theycanbepositionedwithgreateraccuracy.
B.CommonIliacArtery
Thecommoniliacarteryisastraightandimmobilevessel,beingfixedtothesacralpromontory,whilethe
external iliac artery has a much more tortuous course, stretching during hip extension. Open surgical
procedures have excellent patency rates but are associated with significant morbidity and mortality.
Severalrandomizedstudiescomparingendovascularstentingwithstand-aloneangioplastydemonstrated
stentingtobesuperiorinbothhemodynamicparametersandRutherfordclassification.Ameta-analysisof
iliac intervention showed that stent placement reduced the risk of long-term failure by 39% when
compared with PTA alone.2 Table 13.1 lists all current FDA (U.S. Food and Drug Administration)–
approvedballoon-expandablestents.
Table13.1
FDA-ApprovedBalloon-ExpandableBare-MetalStentsinLowerExtremityPeripheralArterialDisease
DeviceName Manufacturer Material
Used
Guidewire
Size/Endhole
(inch)
IntroducerSize
(F)
Stent
Diameter
(mm)
StentLength
(mm)
Delivery
System
Length(cm)
FDA
Approval
Omnilinkelite Abbott
Vascular
Cobalt
chromium
0.035 6,7 6-10 12,16,19,29,
39,59
80,135 Iliac
ExpressLD
Iliac/Biliary
Premounted
Boston
Scientific
316L
Stainless
steel
0.035 6(upto
8×37mm),7(up
to10×57mm)
6-10 17,25,27,37,5775,135 Iliacand
biliary
PalmazIliac Cordis 316L
Stainless
steel
0.035 10 8-12 30 NA Iliac
PalmazIliacand
Renal
Cordis 316L
Stainless
steel
0.035 6,7 4-8 10,15,20,29 NA Iliacand
renal
AssurantCobalt
Iliac
Medtronic Cobalt
chromium
alloy
0.035 6 6,7,8,9,1020,30,40,60 80,130 Iliac
Visi-Pro Medtronic 316L
Stainless
steel
0.035 6(5-8mm),7(9-
10mm)
5,6,7,8,
9,10
12(5-7mm
diameters),17,
27,37,57
80,135 Iliacand
biliary
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FDA,U.S.FoodandDrugAdministration.
III.Balloon-ExpandableCoveredStents
A.GeneralPrinciples
Coveredstentscanbeusedtotreataneurysms,perforations,andarteriovenous fistulaeintheaortoiliac
region.Opensurgeryisthepreferredapproachforcomplexandsevereiliacarteryocclusivediseasein
low-risk patients. More recently, endovascular intervention has been performed with acceptable
outcomeseveninTASCCandDlesions.Theuseofcoveredstentshasbeenproposedtoreduceintimal
hyperplasiaandtoimprove long-termpatencybyreducingrestenosis.TheAtriumiCASTcoveredstent
(Maquet Getinge Group, Rastatt, Germany) and the Viabahn VBX endoprosthesis (W.L. Gore &
Associates, Flagstaff,AZ) are twocommercially available balloon-expandable polytetrafluoroethylene
(PTFE) covered stents. Although the iCAST stent is currently approved by the FDA to treat
tracheobronchial strictures, it has been used “off-label” in aortoiliac, mesenteric, and renal arterial
occlusivedisease.TheViabahnVBXstentwasrecentlyapprovedbyFDAasthefirstballoon-expandable
stentgraftforuseintheiliacartery.
1. TheiCASTcoveredstent isa 316Lstainless steelballoon-expandablestent,whichisencapsulated
entirelywithathinPTFEfilm.Thestentgraftispremountedonanoncompliantballoonandiscompatible
witha6or7Frsheath.Itisavailablein5to10mmdiameterandin16,22,38,and59mmlengths.The
deviceisavailablein80cmand120cmshaftlengthsandisdeliveredona0.035-inwireplatform.The
stent can be postdilated to 4 mm larger if necessary after deployment, but this results in stent
foreshortening.TheiCAST stent is stiffer than a bare-metal stent(BMS) ofcomparable size,and care
shouldbetakenwhenitisadvancedthroughseverelystenoticorocclusivelesionsowingtotheriskof
stentdislodgement.
2. The Viabahn VBX endoprosthesis is composed of a stainless steel stent fully covered in a
fluoropolymer,whichis coatedwith bioactive heparinsurface. The stentis premounted on a 0.035-in
guidewire-compatible delivery system and requires a 7 or 8 Fr sheath. It is available in 5-10 mm
diameterandin15,19,39,and59mmstentlengths.SimilartotheiCASTstent,theViabahnstentcanbe
postdilatedtoalargerdiameterifneeded.
B.ComparisonwithBare-MetalStents
Thereareafewretrospectiveseriesandonlyonerandomizedcontrolledtrialcomparingtheoutcomesof
balloon-expandable covered versus bare-metal stents (BMSs) in the treatment of severe aortoiliac
occlusivelesion.Oneretrospectivereview,consistingof54patientsshowedsuperiorpatencyat2years
with the use of covered balloon-expandable stents for aortic bifurcation occlusive disease.3 Others,
however, showed comparable or worse outcomes of covered stents in severe iliac artery obstructive
lesions.
4,5
Inaretrospectiveseries,whichincluded128patientsfromItaly,earlyandmidtermoutcomes
were comparable between covered and bare-metal balloon-expandable stents. The only benefit for
coveredstentswasinTASCIIDlesionswithlonglesionsofthecommonandexternaliliacarteries.4In
anotherseries,BMSwas reportedtohavesignificantlybetterpatency comparedwithcoveredballoonexpandablestents.
5
C.CoveredVersusBalloon-ExpandableStentTrial(COBEST)
The Covered Versus Balloon-Expandable Stent Trial (COBEST) enrolled 125 patients at 8 major
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Australian centers to determine whether covered stents were superior to BMS in the treatment of
aortoiliacocclusivediseasewithboth1-year6andsubsequent5-yearoutcomesreported.7Overall,stent
patencywasfoundtobesimilarwithcoveredstentsandBMS.Insubgroupanalysis,thepatencyratefor
covered stents was significantly higher thanBMS at18 months,andthis persisted up to 60monthsin
TASC C and D lesions.
6,7
Although patients who received covered stents received fewer
revascularizationproceduresinthetrial,thechoiceofcoveredstentversusBMSdidnotaffecttherateof
limbamputation.7Arecentmeta-analysisthatincluded255diseasedarteriesin182patientsshowedno
significantimprovementinprimarypatencywithcoveredstents.
8
D.Summary
Insummary,theresultsofballoon-expandablecoveredstentsandBMSaresimilarinaortoiliacocclusive
disease.Currentliterature doesnot supporttheroutineuse ofballoon-expandable covered-stent grafts,
althoughthereissomeevidencetosuggestimprovedpatencyformoreadvancedTASCCandDlesions.
Theyremainanimportanttherapeuticoption,however,forbailoutofperforationsorforcomplexlesions
atriskofruptureduringintervention.
IV.Self-ExpandingStents
A.Wallstent
1.Self-expandingWallstents(BostonScientific,Marlborough,MA)werefirstdeployedintheSFAinthe
late1990sbutwere quicklyshowntobe inferiortonitinolself-expanding stentswitharelativelyhigh
rateofstrutfracture.9WallstentsaremadeofElgiloy,a“superalloy”combiningcobalt,chromium,nickel,
molybdenum, manganese, and a relatively small amount of iron. It is therefore nonferromagnetic and
magneticresonanceimaging(MRI)compatible.Theplatinumcorerendersthisstentradiopaque.Ithasa
braided,tubularwoven-meshdesign,whichimpartsflexibilityandanoutwardself-expandingforcetothe
stent. These unique design characteristics impart an ability to recapture the stent even when 87%
deployed, allowing it to be repositioned during deployment. The woven-mesh configuration of the
Wallstent causesittoadaptitsdiameter to thewidth ofthevessel lumencomparedwithnitinol stents,
whichexpand toapredetermineddiameter.Thelengthofa deployedWallstentismore variable,being
dependentonthevesseldiameter,thereforesusceptibletoforeshorteningortheopposite.
B.NitinolSelf-ExpandingStents
1. The introduction of nitinol self-expanding stents changed the treatment of femoropopliteal
endovasculardisease,movingstentimplantationfromprimarilyabailoutprocedureafterfailedballoon
angioplasty to a reasonable initial approach. Nitinol is a metal alloy of nickel and titanium, which
exhibits two unique and closely related properties: shape memory effect and superelasticity. Shape
memoryis theabilityofnitinoltoundergodeformationatonetemperatureandthenrecoveritsoriginal
shapeat a higher temperature.Nitinolstentshaveimproved radialstrength andreducedforeshortening
andcrushresistanceowingtotheaboveuniqueproperties,makingthemwellsuitedforuseintheSFA,
the longest artery in the human body, subject to flexion, extension,lateral compression, and torsional
forcesduringdailyactivity.
2. Nitinol self-expanding stents have not been shown tobe superior over angioplasty for short, focal
lesions.TheFAST(FemoralArteryStentingTrial)randomized244patientswithlesionsbetween1and
10 cm to angioplasty versus primary stent implantation. Despite higher initial technical success, no
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differenceswereseenat12-monthfollow-upinultrasound-assessedbinaryrestenosisrates,targetlesion
revascularization,orRutherfordcategory.
10
3. For lesions of intermediate length, however, self-expanding nitinol BMSs have been shown to be
superior to balloon angioplasty. An important early trial, the Vienna Absolute study, randomized 104
patients toprimary nitinol stenting versus balloon angioplastywith optional secondarystenting. Mean
lesionlengthwas 13.2cm inthe stentgroup, andsecondarystenting was performedintheangioplasty
groupin32%ofpatients.Therestenosisrateandtreadmillwalkdistanceweresignificantlysuperiorin
theprimarystentedgroupat6-and12-monthfollow-up.11Subsequentstudieshavesupportedthisinitial
finding.
12,13
C.Summary
Inroutineclinicalpractice,manypatientshavemuchlongerSFAlesionsthanthosestudiedinrandomized
trials,whichare associatedwith high restenosisrates.14Restenosisis difficulttotreatandassociated
withworseclinicaloutcome.Forthisreason,self-expandingnitinolBMSsarecurrentlymainlyusedin
conjunctionwithplainballoonangioplastyordrug-coatedballoonangioplastytospotstentsegmentswith
unsatisfactory angioplasty results in external iliac, superficial femoral, or popliteal arteries. All selfexpanding,FDA-approvedstentsforthelowerextremitiesarelistedinTable13.2.
Table13.2
FDA-ApprovedSelf-ExpandableBare-MetalStentsinLowerExtremityPeripheralArterialDisease
DeviceName Manufacturer MaterialUsed Guidewire
Size/Endhole
(inch)
Introducer
Size(F)
Stent
Diameter
(mm)
StentLength
(mm)
Delivery
System
Length
(cm)
FDA
Approval
AbsolutePro AbbottVascular Nitinol 0.035 6 6,7,8,9,1020,30,40,60,80,
100
80,135 Iliac
Supera AbbottVascular Nitinol 0.018 6 4.5,5,
5.5,6,
6.5
20,30,40,60,80,
100,120,150
120 SFAand
proximal
popliteal
E-Luminexx
Vascularand
Biliary
BardPeripheral
Vascular
Nitinol 0.035 6 7,8,9,10 20,30,40,60,80,
100
80,135 Iliacand
biliary
LifeStar
Vascularand
Biliary
BardPeripheral
Vascular
Nitinol 0.035 6 7,8,9,10 20,30,40,60,80,
100
80,135 Iliacand
biliary
LifeStentSolo
Vascular
BardPeripheral
Vascular
Nitinol 0.035 6 6,7 200 100,135 SFAand
full
popliteal
LifeStentand
LifeStentXL
Vascular
BardPeripheral
Vascular
Nitinol 0.035 6 5,6,7 20,30,40,60,80,
100,120,150,170
80,130 SFAand
full
popliteal
Astron Biotronik
(distribuedby
Getinge/Macquet)
Nitinol 0.035 6 7,8,9,10 30,40,60,80 72,130 Iliac
Epic BostonScientific Nitinol 0.035 6 6,7,8,9,
10,12
20,30,40,50,60,
70,80,100,120
75,120 Iliac
Innova BostonScientific Nitinol 0.035 6 5,6,7,8 20,40,60,80,
100,120,150,200
75,130 SFA
Wallstent
Endoprosthesis
BostonScientific Elgiloy 0.035 6 6,7,8,9,1018,20,23,24,34,
35,36,38,39,46,
47,49,52,55,59,
61,66,67,69
75,135 Iliac
Zilver518 CookMedical Nitinol 0.018 5 6,7,8,9,1020,30,40,60,80 125 Iliac
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Zilver635 CookMedical Nitinol 0.035 6 6,7,8,9,1020,30,40,60,80 80,125 Iliac
SmartControl
Iliac
Cordis Nitinol 0.035 6 9,10 20,30,40,60 80,120 Iliac
SmartControl
Vascular
Cordis Nitinol 0.035 6 6,7,8 20,30,40,60,80,
100
80,120 Iliacand
SFA
Smart
Vascular
Cordis Nitinol 0.035 6 6,7,8 120,150 120 SFA
GoreTigris Gore Nitinol/ePTFE 0.035 6 5,6,7 40,60,80,100 120 SFAand
proximal
poplitealup
to240mm
inlength
CompleteSE Medtronic Nitinol 0.035 6 5,6,7,8,
9,10
20,40,60,80,
100,120,150
80,130 Iliac,SFA,
and
proximal
popliteal
EverFlex—
SFAandPPA
Medtronic Nitinol 0.035 6 6,7,8 20,30,40,60,80,
100,120,150,200
80,120 SFAand
proximal
popliteal
EverFlex—
Iliac
Medtronic Nitinol 0.035 6 6,7,8 20,30,40,60,80,
100,120
80,120 Iliac
ProtegeGPS Medtronic Nitinol 0.035 6 9,10,12 20,30,40,60,80 80,120 Iliac
MisagoRX Terumo Nitinol 0.035 6 6,7,8 40,60,80,100,
120,150
135 SFAand
proximal
popliteal
FDA,U.S.FoodandDrugAdministration;PPA,proximalpoplitealartery;SFA,superficialfemoralartery.
V.Self-ExpandingCoveredStents
A.GeneralPrinciples
Despite continued advances in SFA endovascular intervention, TASC II C and D lesions remain a
technical challenge with poor primary patencyrates due to in-stent restenosis and stent fracture. The
length and complexity of an SFA lesion are the most important factors linked to such failure.
Theoretically,astentgraftintheSFAwithcontinuousexclusionofthevesselwallfromluminalflowmay
preventneointimaltissuegrowth,reducingtheriskofin-stentrestenosisandthrombosiscommonlyseen
withBMSsinadditiontoprovidingprotectionfromdistalembolizationduringdeployment.Onepotential
drawbackofastentgraft,however,isthepossibleexclusionofimportantcollateralbranches,whichmay
worsenpretreatmentsymptomsorleadtolimbischemiaintheeventofagraftthrombosis.Thisproperty
ofexclusionisusedspecifically,however,inthetreatmentofpoplitealarteryaneurysms.
B.ClinicalUseinPeripheralArterialDisease
1.FDAApproval
a. TheonlyFDA-approvedself-expandingstentgraftinthetreatmentoflowerextremityperipheral
arterialdiseaseistheViabahnEndoprosthesis(W.L.Gore&Associates,Flagstaff,AZ),aflexible,
self-expanding covered-stent graft. The expanded polytetrafluoroethylene (ePTFE) lining is
supported externally by a nitinol stent throughout its entire length and is now available with a
heparin-bondedsurface,whichmaydecreasethelikelihoodofstentthrombosis.15Anon–heparin-
bondedversionisalsoavailableforpatientswithahistoryofheparin-inducedthrombocytopenia.It
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firstbecameavailableintheUnitedStatesin2002andwassubsequentlyapproved bytheFDAin
2005forSFAintervention.
b. Itisavailablein5-8mmdiameterswithalengthbetween2.5and25.0cm.Thedeviceisdeployed
eitherthrougha6-to8-Frenchsheathona0.018″wireplatformorthrougha7-to8-Frenchsheath
over a 0.035 ″ platform. Larger devices intended for the iliac artery are available in 9-13 mm
diametersand2.5-15.0cmlengths.Theselargerdevicesarebuiltona0.035″guidewireplatform
andrequirea9-Frenchorlargersheath.
2.RandomizedControlledTrials
a. Todate, a number ofpublishedrandomizedcontrolled trials have evaluated theuse ofa Viabahn
stentgraftinthetreatmentofSFAocclusivedisease.
16-19
Thefirsttrial,reportedin2009,compared
the efficacy of Viabahn stent grafts with a prosthetic femoral to above-knee popliteal bypass in
patientswithTASC-IIAthroughDlesions.Primarypatency(59%vs58%,P=.81)andsecondary
patency(74%vs71%,P=.89)ofthestentgraftandsurgicalbypasswerecomparableupto4years
16
Twootherrandomizedcontroltrialscomparedtheefficacyofacovered-stentgraftandaBMSin
complexfemoropoplitealarteriallesions.
17,19
Inthefirst,theVIASTARtrial,the12-monthprimary
patencywassimilarbetweenthestentgraftandtheBMS(70.9%and55.1%,respectively,P=.11),
basedonanintention-to-treatanalysis.19Thebenefitofthestentgraftwasmoreprominentinlong
SFAlesions.The12-monthpatencyforpatientswitha>20cmSFAlesionwassignificantlybetter
for thestent graftthan BMS,(71.3% vs 36.8%, respectively, P = .01). Updated in2015, 2-year
resultsfor theVIASTARtrial showedsustained benefit ofthestentgraftover BMS,especially in
patientswithlongSFAlesions.Interestingly,freedom-from-reinterventionandbypasssurgeryrates
were similar after the stent graft and BMS for lesions <20 and ≥20 cm. The second trial, the
VIBRANTtrial,showednosignificantdifferencesinprimarypatencyratesat3yearsbetweenthe
Viabahn stent graft and BMS, respectively (24.2% vs 25.9%), for TASC-II C and D lesions.
17
Although boththe stentgraft and the BMS had reasonable outcomes inthe firstyearafter device
implantation,long-termprimarypatencywasgenerallypoorinpatientswithcomplexSFAlesions.
b. TheViabahnstentgrafthasbeenevaluatedfortreatmentofSFAin-stentrestenosis.20Eighty-three
patients with SFA in-stent restenosis and Rutherford category 2-5 ischemia were enrolled in 7
European sitesandrandomizedtoreceive theViabahn stent graft orstandardballoonangioplasty.
Fortreatmentofin-stentrestenosis12-monthpatencyratesweresignificantlybetterinthestentgraft
group(74.8%vs28%respectively,P<.001),fortreatmentofin-stentrestenosis.Likewise,ametaanalysis,whichincludedfourprospectiverandomizedtrials,oneretrospectivetrial, andninecase
series, showed that at 1 year, a covered-stent graft in the SFA has better outcomes than other
interventions,includingballoonangioplastyandBMS.21Therateofstentfracturesinlonglesions
wassignificantlylowerwithstentgrafts.
1.AntiplateletandAntithromboticTherapy
Despitethelackofconsensusguidelinesonantiplateletorantithrombotictherapypostperipheralstenting,
therehavebeentheoreticalconcernsofincreasedstentthrombosisincoveredgrafts.Optimalpost–stent
graft medical therapy is unknown and has not beenstudied in a randomized fashion. Evaluation ofa
nonrandomized retrospective series of patients treated with aspirin and clopidogrel for 6 weeks post
interventionversusaspirinandclopidogrelindefinitelyintheabsenceofbleedingcomplicationsversus
triple therapy (aspirin, clopidogrel, and anticoagulation) in patients with other indications for
anticoagulation showed no difference in patency with the different aspirin and clopidogrel treatment
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strategies. There was, however, a significant benefit with triple therapy in comparison to temporary
clopidogrelinlong-termpatency,whichwas,however,off-setbybleedingcomplications.
22
2.Summary
Covered-stent grafts are used as a safe option for the treatment of symptomatic SFA lesions, with
reasonabletechnicalsuccessandreasonableshort-termpatencyoutcomes.Althoughlong-termpatencyis
equivalenttoaBMS,thestentgraftmighthavethetheoreticalbenefitofreducingin-stentrestenosisand
stentfracture. Finally, itis useful forthe treatment of in-stentrestenosis andperforationand maybe a
less-invasive option for patients who need a prosthetic above-the-knee bypass. The technical
characteristicsandfeaturesofbothViabahnstentgraftsarelistedinTable13.3.
Table13.3
FDA-ApprovedSelf-ExpandingStentGraftsinLowerExtremityPeripheralArterialDisease
DeviceName Manufacturer MaterialUsed Guidewire
Size(inch)
Introducer
Size(F)
Stent
Diameter
(mm)
Stent
Length
(mm)
Delivery
System
Length
(cm)
FDA
Approval
GoreViabahn
Endoprosthesis
Gore Nitinol/ePTFE,
gold
0.035 7-12 5,6,7,8,
9,10,11,
13
25,50,
100,
150
75,120 Iliac,
SFA,and
AV
access
grafts
GoreViabahn
Endoprosthesiswith
heparinbioactivesurface
Gore Nitinol/ePTFE,
gold
0.018/0.014
(5-8mm),
0.035(513mm)
6-12 5,6,7,8,
9,10,11,
13
25,50,
75,
100,
150,
250
75
(0.035inch
endhole
only),120
Iliac,
SFA,and
AV
access
grafts
AV,arteriovenous;FDA,U.S.FoodandDrugAdministration;SFA,superficialfemoralartery.
VI.SuperaNitinolSelf-ExpandingBareMetalStent
A.PeipheralStentsandRiskofStrutFracture
Strut fracture is a common issue with traditional laser-cut nitinol tube self-expanding stents in the
infrailiac vessels of the lower extremity owing to significant rotational and flexional stressors
encounteredinnormalmovement.Strutfracturespredisposetowardrestenosisandleadtoareductionin
primary patencypost peripheral intervention.To address this common issue,the Supera stent (Abbott
Vascular,SantaClara,CA),aninterwoven,braidednitinol,helicalself-expandingBMS,wasdeveloped
withdesignfeatures,whichdramaticallyreduce thefracture rate,increasemultidimensionalflexibility,
andresultinexcellentradialstrength.Thebiomimeticpropertiesofthestentenablethestenttoflex,bend,
andmovewiththevessel,distributingstressevenly.
B.SuperaStent
1.TheSuperastentisavailablein4.5-6.5mmdiametersandlengthsrangingbetween20and150 mm,
delivered via a 6-Frenchcatheter and a0.018 ″ end-holesystem. Itis primarilyusedclinically in the
treatmentofsuperficialfemoralandpoplitealstenosisoneitherdenovoorrestenoticlesions.
2. Owing to its unique characteristics, deployment requires careful vessel preparation techniques,
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specific to the stent. The vessel should be predilated to achieve a 1:1 matchbetween the stent outer
diameterandthepostdilationvesselcaliber.Thereshouldnotbemorethan1-mmoversizingofthestent.
The deliverycatheter mechanismallowsforprecise releaseofthehelicalcoils viathumb movements,
allowing for control of the deployed length. This also leads to the ability to increase the density of
deployedcoilsifdesiredtoincrease radialstrengthinspecific sectionsofthestent.Thestentismuch
longer within the delivery catheter compared with the deployed length, occasionally leading to
compressed or elongated deployment of the stent length in untrained hands. This feature makes it
unsuitableforuseinostiallesions.
1.SUPERBTrial
a. TheclinicalperformanceoftheSuperastentisbestrepresentedbytheSUPERBtrial,the
SUPERSUBstudy,andtheLeipzigregistries.Notably,nostrutfractureshavebeenrecordedinany
ofthereportedclinicaltrialstodateduringfollow-up.TheSUPERBtrialwasanonrandomized,
prospective,multicenter,investigationaldeviceexemption,single-armtrial,whichenrolled264
patientsundergoingtreatmentofdenovoorrestenoticlesionsoftheSFAorproximalpopliteal
artery.AlmostalllesionsinthestudywereintheSFAwithanaveragelesionlengthof78mm.Early
safetyasevaluatedbyfreedomfromdeath,targetvesselrevascularization,oranyamputationofthe
indexlimbat30dayspostprocedurewasachievedin99.2%ofpatients.Primarypatencyat
12monthswas86.3%.23TheLeipzigSUPERA500registryreported2-yearsingle-centeroutcomes
on492limbsin439unselectedpatientstreatedwiththeSuperastent.Primarypatencywas83.3%at
12monthsand72.8%at2years.Secondarypatencywas98.1%and92.0%,respectively.No
differencewasnotedinSFAversuspopliteallesions.24SUPERSUBwasasingle-center,
prospective,single-armstudy,whichreported1-yearoutcomeintheuseofSuperastentsinlong
femoropoplitealcompleteTASCCandTASCDocclusionstreatedviasubintimalrevascularization
withanaveragelesionlengthof279mm.Primarypatencyat1yearwas94.1%,andfreedomfrom
TLRwas97.1%.25TheLeipzingSUPERApoplitealarterystentregistryreported12-month
retrospectiveoutcomeson101patientsundergoing125stentswithanaveragelesionlengthof
84mm.The6-and12-monthprimarypatencyrateswere94.6%and87.7%withsecondarypatency
ratesof97.9%and96.5%,respectively.
26
b. Thesefindingshavebeenborneoutinseveralreal-worldregistries,additionallyconfirmingthetotal
absenceofstrutfractures.
27-30
Althoughexceedinglyrare,asinglecasereportintheliterature
suggeststhatwhenstrutfracturesdooccur,thepeculiardesignofthestentmaypredisposethebreak
toresultinthecompletelossofintegrityofthestent.
31
In conclusion,althoughthe Supera stenthas notbeenstudiedinarandomizedfashion, itconstitutesan
important advance instent design, with its extreme flexibility, higher radial strength,anddramatically
lowerstrutfracturerate.Thesedesignfeaturesmakeitidealandpreferredforuseinthepoplitealartery,
when stents are indicated due to the extreme biomechanical forces imposed on this segment from
repetitive knee flexion.32 Careful attention mustbe paid todeployment ofthe stent, due to its unique
features,andoperatorsshouldbewell-versedindeploymenttechnique.
VII.Drug-ElutingSelf-ExpandingStents
GiventhehighratesofintimalproliferationfollowingPTAwithorwithoutdeploymentofBMSsandhigh
rateofin-stent-restenosis,antiproliferativetherapieshavebeenusedinperipheralarterialdiseaseswith
drug-coatedballoonsanddrug-elutingstents(DES).
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A.First-GenerationPeripheralDrug-ElutingStents(DES)
1.First-generationdrug-elutingstents(DES)usingsirolimusdidnotprovideadditionalclinicalbenefit
when compared with BMSs. The failure of first-generation DES delivering two different doses of
sirolimuswasattributedinparttorapiduncontrolleddrugrelease.33Thisledtothedevelopmentofthe
everolimus-eluting stent, incorporating a copolymer for slower more efficient drug release. Although
initialnonrandomizedstudiesconfirmedthesafetyandefficacyofthetechnology,itonlyachieved68%
patencyat1year.
34
B.PaclitaxelPeripheralSelf-ExpandingStents(ZilverPTX)
2.Whileinitialfirst-generationDESachieveddiscouragingoutcomesinperipheralarterydisease(PAD),
theuseofpaclitaxel-elutingDESwasontheriseincoronaryarterieswithsuperioroutcomescompared
with BMS. Despite both paclitaxel- and limus-type drugs expressing antiproliferative properties,
paclitaxelishighlylipophilic,whichpermitshighproteinbindingandexcellenttransmembranepassage,
resultinginhighintracellularconcentrations inthesubintimallayers.35Followingthesuccessful useof
paclitaxelasanantiproliferativetherapyindrug-coatedballoonsystemsforfemoropoplitealterritories,
twonovelstentsystemsforthelowerextremityhavebeendevelopedusingthesameagent,withonlyone
systemcurrentlyFDA-approvedforclinicaluse.TheZilverPTX(CookMedical,Bloomington,IN)isan
open-cell, flexible, self-expanding nitinol stent with a polymer-free paclitaxel coating. The stent is
enclosedwithinasheathbeforedeploymentatthetargetvessellocationandiscoatedonlyontheouter
surface, which traps paclitaxel between the stent struts and the vessel wall after deployment. Unlike
standard DESusedin coronary arteries, theZilver PTXstructure does notincludea copolymer, with
rapiddrugreleasepeakingtypicallywithintheinitial14daysafterdeploymentfollowedbyadramatic
decrease.
36
1.ZilverPTX
a. TheZilverPTXiscurrentlyavailableindiametersfrom5to10mmandlengthsfrom20to80mm,
deliveredviaa6-Frenchsystem.Itisdesignedforuseinabove-the-kneefemoropoplitealarteries
havingreferencevesseldiameterfrom4to9mm,eitherde-novoorrestenoticlesions,typicallyafter
balloonangioplasty.Predilatationbeforestentplacementisroutinelyrequired.Giventheabsenceof
polymerbindingpaclitaxeltothestentandtheoutercoatingofthestentsurface,manualhandlingof
the stent is contraindicated, and care mustbe taken while handling the stent not to wash out the
paclitaxelcoatingbeforestentdeployment.
b. The ZilverPTXrandomized clinical studytestedtheeffectivenessofZilverPTXinSFA lesions,
randomizing439 patientseithertoprimaryDESimplantationor toPTAalone. Compared withthe
PTA group, the primary DES group exhibited superior 12-month event-free survival (90.4% vs
82.6%;P=.004)andprimarypatency(83.1%vs32.8%;P=.001).Ofnote,120patientshadacute
PTAfailureandunderwentsecondaryrandomizationtoprovisionalDES(n=61)orBMS(n=59).
ComparedwithBMS,provisionalDESexhibitedsuperiorprimarypatency(89.9%vs 73.0%;P=
.01) and superior clinical benefit (90.5% and 72.3%, P = .009).37 Recently, 5-year follow-up
confirmedthe sustainability of earlier findings,with primarypatency at5 years of 64.9% for the
primaryDESgroupincomparisonwith19%forthePTAgroup.38ThedevicefeaturesoftheZilver
PTXstentarelistedinTable13.4.
Table13.4
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FDA-ApprovedDrug-ElutingStentsinLowerExtremityPeripheralArterialDisease
Device
Name
Manufacturer Material
Used
Drug
Delivered
Guidewire
Size(inch)
Introducer
Size(F)
Stent
Diameter
(mm)
Stent
Length
(mm)
DeliverySystem
Length(cm)
FDA
Approval
Zilver
PTX
Cookmedical Nitinol Paclitaxel 0.035 6 6,7,8 40,60,80,
100,120
125 SFA
FDA,U.S.FoodandDrugAdministration;SFA,superficialfemoralartery.
C.Drug-ElutingSelf-ExpandingStentsIn-Development
A new DES system is currently being tested for use inthe femoropopliteal arteries. The Eluvia DES
(BostonScientific,Marlborough,MA)isanitinolself-expandingstent.However,unliketheZilverPTX,
thissystemdesignincludesanactivelayerofthefluoropolymerPVDF-HFP(poly[vinylidenefluoride-cohexafluoropropylene]), which is the coating polymer on the Promus Element coronary stent (Boston
Scientific,Marlborough,MA)tocontrolpaclitaxelrelease over longerperiods. Initialdata reporteda
stunningprimarypatencyof96%at12-monthfollow-up.39Randomizedtrialswithlongertermfollow-up
arecurrentlyinprogress.
VIII.BioresorbableScaffolds
A.GeneralPrinciples
With unsatisfactory primary patency rates after endovascular therapy with angioplasty or stents,
bioresorbablescaffold(BRS)systems are being developed fortheir theoretical benefitsofmaintaining
further diagnostic and therapeutic options in the long term, such as follow-up MRI, repeated
revascularizationviaendovascularapproach,orbypasssurgery.
The most common scaffold system is composed of poly-L-lactide (PLLA), whichtypically resorbs to
carbon dioxide and water over 2-3 years.40 The second, less popular BRS system is metal based
(magnesium andotherminerals)andhasbeenusedbelowthekneeswithunfavorable outcomes,mostly
related to very rapid resorption and lower radial strength.41 Newer PLLA BRS incorporate the
antiproliferativeagenteverolimus,withaBRScopolymertocontroldrugreleaseintothesubintimallayer
similar to the recently discontinued ABSORB (Abbott Vascular, Santa Clara, CA), bioabsorbable
coronarystent.
C.The unique aspects of BRS stents are not only limited to their composition and the advantage of
resorption, as such advantagecomesata greatcostofstrut thickness. Typically, BRS struts are about
twice as thick as traditional metal stents with lower radial strength and flexibility, leading to lower
deliverability.AsmostBRSsareradiolucent,fluoroscopicvisualizationoftheactualstentisimpossible,
and most stents have radiopaque markers to facilitate visualization. These factors contribute to a
deploymentprocess, which tends to be less forgiving, requiring careful technique and training. Other
technicalaspectsincludeproblemswithoverlappingmultiplestents,secondarytothickerstruts,causing
longeroverlappingsegmentstoincreasethelikelihoodofstentthrombosis.PostdilationofBRSshouldbe
limited,as theydo notprovide comparable radial strength to metalstents and are moresusceptible to
fracture if postdilated beyondtheir prespecified nominal pressures. These factors significantly impact
outcomesofBRStechnology.
42
B.LowerExtremityClinicalTrials
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