6颈动脉狭窄的血管内治疗3
Stent
支架
Severalstentswithvaryingcharacteristicshavedisplayedefficacyintrialsandregistries(Table21.1);however,aclosed-cellstentwithafree-cellarea(theuncoveredareabetweenthestrutsofthestent)thatissmallispreferredformostcarotidstentingcases.38,39Aclosed-cellstentenablesrecaptureafterpartialdeploymentintheeventofmalpositioningandlimitstheriskofdistalembolicprotectiondevicesbeingcapturedonthefreeedgesofthestent.Themostimportantattributeofclosed-cellstentsisthatthefree-cellareaismuchsmallerthanthatofopen-cellcounterpartsandconstrainsplaqueandsubsequentlyitsdebrisfrombeingreleasedintothevessellumen.Thisessentiallyservesasthemostimportantformofpostprocedureembolicstrokeprophylaxisasevidencedbymostipsilateralstrokesbeingreportedpostprocedurebetweendays1and30.28,40However,thedrawbackoftheclosed-cellstentdesignisthatthesestentstendtobeinflexibleanddonotconformwelltothevesselwall,resultinginstraighteningofthevesselinthestentedsegment,andifthereisseverevesseltortuosity,eitheraproximalordistalkinkcanresult,whichcanbeflow-limiting.Instead,incasesofvesseltortuosityatthesiteofstenosis,anopen-cellstentmaybepreferabletoconformtothevesselandavoidtheriskofkinkingofthestentedvessel.Stentswithsmallfree-cellareastheoreticallytrapplaqueparticulatesbetweenthestentandthevesselwall,therebylimitingtheriskofthromboembolism.41AstentofsufficientlengthshouldbeselectedtocovertheentirelesionandbridgetheICAtotheCCA.
在试验和登记研究中，几个具有不同特征的支架显示出有效性（表21.1）；然而，具有游离区的密闭网状支架（在支架之间的裸露区域），在大多数颈动脉支架置入术中，多选择较小的支架[38、39]。密闭孔支架在部分放置错误后能够重新放置和减少支架边缘捕获的远端栓子保护装置风险。闭孔支架最重要的特性是游离孔的面积比开放孔的面积小得多，限制斑块和随后的碎片释放到血管腔。这基本上是预防术后栓塞性脑卒中的最重要形式，因为据报道大多数同侧脑卒中发生在术后1至30天[28,40]。然而，封闭网孔支架设计的缺点是，这些支架不灵活，和血管壁贴合不佳，导致支架段血管拉直，如果有严重的血管迂曲，要么会导致近端或远端的扭结，限制血流量。相反，在血管迂曲的狭窄部位，开放式网孔支架更容易贴合血管，避免支架血管扭结。小网孔自由区支架理论上阻止支架和血管壁之间斑块微粒的形成，从而减少血栓源性栓塞风险[41]。有足够长度的支架应选择覆盖整个病变并将ICA与CCA连接。
AngioplastyBalloon
球囊血管成形术
Althoughprestentangioplastyisperformedroutinelyatsomecenters,itistheauthors’preferencetoperformprestentangioplastyonlyinthosefewcaseswherethestentmaynotbeeasilyorsafelypassedwithoutanangioplasty.42Poststentingangioplastyisperformedinmostcasesforproperresolutionofthesiteofgreateststenosis.Forpoststentangioplasty,anangioplastyballooncatheterisselectedtobeslightlyundersizedtothediameterofthenondiseasedICA.Forproceduralsimplicity(i.e.,tolimitdeviceexchanges)andtolimitthromboembolicpotential,oneangioplastyafterplacementofthestentispreferred.Angioplastyballoonsareavailableinawiderangeofdiametersandlengthstoconformtothevesseldiameterandstentused.Aswithotherdevices,rapid-exchangemechanismsarepreferred.Theconcernwithangioplastyisthatitisconsideredtheportionoftheprocedurewiththegreatestriskofembolizationbecauseitcreatesplaquefracture/ruptureandliberatesplaquedebrisintothevessel.Thisiswhytheauthorslimitangioplastytooneeventafterdeploymentofthestent,whichservestoconstrainsomeoftheplaqueanditsattendantdebriswithinthevesselwall.Inaddition,themoreaggressivetheangioplasty,thehighertheriskofplaquedebrisrelease,hencetheslightundersizingoftheangioplastyballoontonominalICAdiameter.Finally,angioplastyservesasthestrongestactivatorofthevagalresponseduringcarotidarterystenting.Theresultantbradycardia—oritsmanagementwithdopaminergicagonists—mayactuallycausemyocardialischemiainat-riskpatients.Theauthorsthereforelimittheaggressivenessofballoonangioplastyespeciallyinpre–coronaryarterybypasssurgerypatientsandroutinelypretreatallpatientsundergoingcarotidarterystentingwiththecholinergicantagonistglycopyrrolatetosubverttheoccurrenceofbradycardiawithangioplasty.
虽然现今在一些中心常规行血管成形术，作者的偏好是只有在少数情况下使用，如没有血管成形，支架不容易或安全地通过[42]。血管成形术在大多数情况下，可妥善处理狭窄部位。对于支架后血管成形术，血管成形球囊导管的选择要稍小于健侧颈内动脉直径。为了简化操作（即限制设备交换）和限制血栓栓塞，支架置入术后首选血管成形术。血管成形球囊有广泛的直径和长度符合目标血管直径和所用的支架。与其他设备一起，多首选快速交换方式。血管成形术的重点是栓塞的风险较大，因为此操作可造成斑块破裂/碎裂，并将斑块碎片释放入血管。这就是作者将血管成形术限制使用的原因。在支架放置之后，可用来限制一些血管壁内斑块及其伴随的碎片。此外，血管成形术越积极，斑块碎片释放的风险越高。因此直径稍不合适的血管成形球囊使得ICA直径正常。最后，在支架置入时，血管成形容易导致较强的迷走神经反应。由此产生的心动过缓或多巴胺受体激动剂的治疗可能导致高风险患者心肌缺血。因此，作者限制使用球囊成形术，尤其是冠状动脉搭桥手术前患者，所有颈动脉支架置入的患者常规使用胆碱能拮抗剂，预防血管成形术时发生的心动过缓的。
GuideCatheter
导引导管
Aguidecatheterisselectedsuchthatthesmallestarteriotomymaybeusedforsafeplacementofthestent.Formostcases,a6FCookShuttlelongsheath(CookMedical,Bloomington,IN)isusedastheguidecatheter.Thiscatheterhassufficientstiffnesstobeusedasasheathandguidecatheter,whichsimplifiestheprocedureandprovidesastableconduitforcarotidstenting.Withalengthof90cmandaninnerworkingdiameterof0.inch,alldevicecathetersareeasilydeliveredtothesiteofcarotidstenosisthroughtheCookShuttle.Forstentswith5Fdeliverycatheters(e.g.,a6-or8-mmWallstent[BostonScientific,Natick,MA],withadiameterof1.67mm),a6FEnvoycatheter(innerworkingdiameter0.inch;Codman,Raynham,MA)maybeusedasaguidecatheterthrougha6Ffemoralarterysheath.Forpatientswithasmallcarotidarteryandlimitedvesseltortuosity,theEnvoycathetermaybeeasilypositionedproximaltotheareaofstenosis.Itisasufficientlystiffcathetersuchthatthepassageofastentona5Fdeliverycathetermaybeperformedwithouttheguidecatheterherniatingdownwardintotheaorticarch.Forcasesofproximalprotection,a9FMo.Macatheter(forusewiththeMo.Maflowstasissystem[Medtronic,Minneapolis,MN])isemployedastheguidecatheter.AsthesecathetersarelessrigidthantheCookShuttleandhavespecializedtipswithocclusiveballoons,theyarebestusedthroughasheath,necessitatingplacementofa9Ffemoralarterysheath(thesheathneedstobe9Ffor白癜风可以治愈吗白癜风的症状有那些
