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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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FIGURE1.1 Röntgen’sfirstX-rayimageofhiswifeAnna’shand.
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FIGURE1.2 Haschek’sandLindenthal’sfirstangiogramofacadaverichand.
A.InVivoImaging:LimitationsandAdvances
Initially, the toxicity of radiopaque substances limited in vivo imaging. Earl Osborne, a syphilologist
workingatMayoClinic,accidentallydiscovered radiocontrastwhenhe notedthatthe urinary tracts of
syphilis patientstreatedwithoral sodiumiodide agents wereradiopaque.4In 1919,Argentine Carlos
Heuserperformedthe firstvascular studyina living humanbyinjectingdilute potassiumiodideintoa
veinonthedorsumofapatient’shandandfollowingthebolustotheheartfluoroscopically.5InMunich,
BerberichandHirschobtainedthefirstfemoralvenogramin1923byinfusingasolutionofaqueous20%
strontium bromide. Soon after, in 1924, Brooks pioneered intraarterial injection of sodium iodide to
obtain the firstclinical femoral arteriogram.6 Egas Moniz,a French neurologist,initiated carotid and
intracranial angiograpy in 1927 as a means to localized intracranial tumors by their characteristic
vasculature.7Forhiscontributions,hewasawardedthe1949NobelPrizeinPhysiologyorMedicine.
Earlyinorganiccontrastagentswerehighlytoxicandprincipallyusedexperimentally.However,inthe
late1920s,withtheadventofnew,organic,iodine-containingradiocontrastmedia,clinicalangiography
begantodeveloprapidly.WhilesearchingfornewsyphilisremediesinBerlin,BinzandRathdeveloped
the first water-soluble iodinated pyridine contrast called Selectran Neutral.8 In 1933, Swick and
Wallingford synthesizedpara-aminoiodohippuric acid withthreeiodine atomspermolecule,Hippuran,
heraldingthedawnofthemoderneraofpolyiodinatedcontrastagents.9Ioniccontrastmediawithhigher
iodinecontentandimprovedwatersolubilityproliferatedover theensuingdecades;however,thequest
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forlesstoxicmediacontinued.SwedishradiologistTorstenAlménpioneerednonioniccontrastmediain
1969withmonomeric metrizamide(Amipaque);heremainedattheforefrontofthefield withthe1982
releaseofthelow-osmolarmonomeriohexol(Omnipaque)andthe1993introductionoftheiso-osmolar
dimeriodixanol(Visipaque).
10
Concomitant to these advances in contrast media, procedural advances permitted expanded use of
angiography. In 1929, a Berlin surgical residentnamed Werner Forssmann inserted a urinary catheter
throughhisownbasilicveintovisualizehisrightventricle.11Althoughhelosthisjobforthestunt,he
wasawardedtheNobelPrizein1956forhiscontribution.In1953,SwedishradiologistIvarSeldinger
described guidewire technique that allowed reliable access to any major artery or vein.12 Selective
angiography was soon performed in every vascular territory. Notably, however, the first selective
coronary angiogram obtained by Sones at the Cleveland Clinic on October 30, 1958 was performed
inadvertentlyduringaortographywhenthecatheterlandedintherightcoronaryartery.
13
B.TranscatheterVascularIntervention
Transcatheter vascular intervention began in 1964 when Dotter andJudkins used rigid, Teflon-coated
catheterstodilate11femoralandpoplitealstenoses.14Soonafter,Fogartydescribedcatheteraspiration
ofarterial thrombus.15Usinghomemadeequipment,AndreasGrüntzigperformedthefirstiliac double-
lumenballoonangioplastyonJanuary23,1975atUniversityHospitalinZurich16andreportedthefirst
coronaryangioplastyonSeptember16,1977.17Tenyearslater inToulouse, JacquesPuelreportedthe
firstclinical useofa self-expanding coronarystent onMarch 28,1986.18Puel and UlrichSigwart of
Lausannereportedthefirstileofemoralself-expandingstentsin1987.19Laterthatyear,JulioPalmazand
Richard Schatz implanted the first balloon-expandable peripheral and coronary stents.20 Adjunctive
endovascular tools soon followed including intravascular ultrasound (IVUS) in 198821 and coronary
rotationalatherectomyin1989.22Thelast25yearshaveseenaproliferationofdevicestoonumerousto
recount including drug-eluting stents, drug-coated balloons, lesion crossing devices, luminal reentry
devices,andadditionalatherectomymodalities.
III.Fluoroscopy
Fluoroscopic X-rayimagingguides almostall endovascularintervention.Numerous modelsofimaging
equipmentareavailable,butallrelyonthesamefundamentalmechanism.Insideavacuumtube,avoltage
potential (kVp)is applied betweencathode coils and a rapidlyspinning tungstenanode.This potential
resultsinacurrent(mA)ofelectronsbombardingtheanode.Ninety-ninepercentoftheenergygenerated
bythiscircuitisreleasedasheat.Theanodespinsrapidlytodissipatethisheat,andthehighmeltingpoint
oftungstenmakesthiselementthepreferredanodematerial.
Aselectronsflythroughtheanode, a smallminoritypasscloseenoughtoapositivelychargedtungsten
nucleusto be magnetically deflected andslowed. The energyfrom this change in electronvelocity is
released asanX-ray; this phenomenonis called Bremsstrahlung, Germanfor “brakingradiation.”The
energyoftheseX-raysincreaseslogarithmicallywithincreasingkVpduetotheincreasedvelocityofthe
electrons.TheBremsstrahlungX-raybeamisshapedbya collimator,aleadblockwithholesthatonly
allowspassageofX-raysintheintendeddirectionofthebeam,reducingscatter.Copperandaluminum
filtersremovelow-energyX-raysthatdonotcontributetoimaging.
Thepatient’sbodyattenuatesX-raysinproportiontoeachtissue’sdensityandcomponentatomicweights
(“Z”).UnattenuatedX-rays pass throughthe patienttogenerate images.Ina traditionaldigital imaging
system, theseX-rays strike apanelofinputphosphors,whichconvertthe X-rayenergyintolight. This
lightinturnstrikes apanelofphotocathodes, causingtherelease ofelectronsintoanimageintensifier,
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whichincreasestheirenergybyapplyingavoltagepotential.Theseelectronsareabsorbedbyanoutput
phosphor,whichemitslightthatisdetectedbyasiliconarraycharge-coupleddevice(CCD).Theanalog
signal fromthe CCDis relayedtoavideo camera andconvertedbyananalog-digitalconverterintoa
digitalvideosignal(Fig.1.3).
FIGURE1.3 Schematicdiagramoftraditionalimageintensifierandflatpanelsystem.
Innewerflatpanelsystems,lightfromtheinputphosphorstrikesphotodiodes,releasingelectrons.These
electrons are detected directlybya thinfilm transistor array, which producesananalogsignal thatis
converted into a digital video. By avoiding a secondconversionfrom electronsignal to light,the flat
panelprovides higher imageresolution thanthe traditionalimageintensifies. The verynewest systems
mayemployamorphousseleniuminsteadofaninputphosphor.AmorphousseleniumcanconvertX-rays
directlyintoelectrons,bypassingbothtraditionallightconversionsteps.
Digital acquisition permits adjustment of image rendering for several purposes. Automatic image
brightnessfeedbackmodulatesthekVpandmAtooptimizeimaging.Frameratecanbeincreasedwhen
necessarytocapturerapidlymovingobjectsanddecreasedtominimizeX-rayexposure.DSArecordsan
initial imageandsubtractsthatimageas amaskfrom all subsequentframes: the resultis exclusionof
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radiopaquestructuresanddisplayofonlythemovingangiographiccontrastcolumn.
IV.Radiation
Ionizing radiation such as X-rays causes single- and double-strand breaks in deoxyribonucleic acid
(DNA).
A.Patients
Patientsundergoingfluoroscopicallyguided proceduresmaybe acutely exposedtosignificant dosesof
radiation. In the days to weeks following exposure, DNA damage may cause dose-dependent
deterministic effects including skin erythema, epilation, and cataracts23 at doses as low as 2-5 Gy.
Exposure of 10-50 Gy may cause life-threatening hematopoetic, gastrointestinal, and cerebrovascular
syndromes.
24
B.Operators
Procedural operators are chronically exposed to scatter radiation. Both patients and operators are at
stochastic risk for malignancy. The risk of malignancy is not precisely dose-dependent but follows a
linear nonthreshold model. Similarly, DNA damage to reproductive tissues may result in fetal
malformationsandchildhoodmalignancies.TheUnitedStatesNuclearRegulatoryCommissionlimitsthe
annualwhole-bodydosesofradiationusersto50millisieverts(mSv)withspecificlimitsof150mSvto
the lens of the eye and 500 mSv to the skin of the extremities. Pregnant individuals must keep their
exposurebelow5mSvduringthedurationofpregnancy.
C.ProceduralX-rayDosage
SeveralmodifiablefactorsaffecttheproceduralX-raydosage.Operatorsmayreduceradiationexposure
topatients andthemselves by minimizingfluoroscopytime, framerate, magnification, source-to-image
distance,DSAimaging,andsteepangulation,whilemaximizingbeamfiltrationandcollimation,shielding
ofradiation-sensitivetissues,andpersonaldistancefromtheX-raysource.
V.Angiography
X-rayangiography of intravascular contrastdefines thevascular anatomy as a basis for endovascular
intervention. Angiography is used to demonstrate lesion location, morphology, severity, and
collateralizationaswellasthelesion’seffectonbloodflow.Additionally,angiographycandetectvessel
abnormalitiessuchasdissection,thrombosis,andcalcification.High-qualityangiographyisessentialto
guidesafeandeffectiveendovascularinterventionandcanfacilitatedecisionsregardingappropriateness.
A.Angiographers
1. Angiographers mustensure appropriate catheter selection, contrast administration, and fluoroscopy
parameters.
2.Angiographersmustalsoknowwhichimagingprojectionsareidealineachclinicalsituation(Table
1.1;Fig.1.4).
a. Vessels should ideally be visualized in multiple planes perpendicular to the imaging surface,
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althoughinpractice,eachvascularterritoryiscanonicallyimagedinaparticularprojection.
i. Theaorticarchisvisualizedatapproximately30°intheleftanterioroblique(LAO)projection.
ii. Carotidangiographyisperformedatapproximately30°intheipsilateralprojectionandinthe
lateralprojection;subclavianangiographyisperformedatapproximately30°intheipsilateral
and contralateral projections. Intracranial vessels are imaged at approximately 20° cranial
anteroposterior(AP)andinthelateralprojection.
iii. ThedescendingaortaisvisualizedintheflatAPprojection,althougha20°LAOprojectionis
idealfordemonstratingtherenalarteryorigins.
iv. Common iliac artery distal bifurcations are best seen from approximately 30° contralateral
oblique views, whereas the common femoral artery bifurcations are seen best with
approximately30°ofipsilateralobliqueangulation.
v. Tibial and peroneal vessels may be imaged in either the AP or ipsilateral 30° oblique
projections.
b. Pedalangiographyisusuallyperformedlaterally.
Table1.1
OptimalImagingProjectionbyVascularTerritory
VascularTerritory OptimalImagingProjection
Aorticarch LAO30°
Carotidarteries Ipsilateral30°
Lateral
Subclavianarteries Ipsilateral30°
Contralateral30°
Intracranialarteries APcranial20°
Lateral
Descendingaorta FlatAP
Renalarteries LAO20°
Commonandexternaliliacarteries Contralateral30°
Commonandsuperficialfemoralarteries Ipsilateral30°
Tibialandperonealarteries FlatAP
Ipsilateral30°
Pedalarteries Lateral
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FIGURE1.4 Selectedangiogramsatoptimalimagingprojections.A,LAO(leftanterioroblique)30°imageofaortic
arch.B,LAO30°imageofleftcommon,internal,andexternalcarotidarterieswithhigh-gradeinternalcarotid
stenosis.C,RAO(rightanterioroblique)30°imageofleftsubclavianandvertebralarterieswithpatentsubclavian
stent.D,AP(anteroposterior)cranial20°imageofleftinternalcarotidandintracranialarteries.E,FlatAPimageof
descendingaortaandmesentericarteries.F,LAO20°imageofleftrenalarterywithfibromusculardysplasia.G,
RAO30°imageofleftcommonandexternaliliacarteries.H,RAO30°imageofrightcommonfemoral,superficial
femoral,andprofundafemorisarteries.I,LAO30°imageofleftposteriortibial,peroneal,andanteriortibialarteries.
J,Leftlateralimageofleftposteriortibialanddorsalispedisarteriesandpedalarch.
B.PeripheralVascularAngiographyandIntervention
1.Severaldigitalimagingmodesareusedforperipheralvascularangiographyandintervention.
a. Standard low-dose fluoroscopy at 7.5-15 frames per second is used for catheter and wire
manipulationto minimizepatient and operator radiationexposure, especiallygiven the frequently
longfluoroscopytimeduringcomplicatedprocedures.
b. High-resolutioncineangiographyat15-30framespersecond,thestapleforcoronaryintervention,is
seldomusedintheperipheralspace.
c. DSAisthestapleofperipheralvascularimagingtopermitvesselvisualizationdespitethepresence
ofadjacentradiopaquebonesandhigh-velocitybloodflow.
2.Thedegreeofvesselstenosisisreportedasapercentagelumendiameterreductioncomparedwitha
normaladjacentsegmentwithoutaninterveningbifurcation.
a. Quantitativeangiographyusesdigitalcaliperstomakeprecisevascularmeasurements,normalizedto
areferenceofknownsizesuchasacatheter.
i. Digitalimagingsystemsalsofrequentlyincludearoadmapfeature,whichsuperimposesontoa
fluoroscopic imagea partiallytransparent maskofa previouslyrecordedimage.Thisfeature
allowsmanipulationofendovasculartoolswithoutrecurrentcontrastinjectionforvisualization
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ofthevascularanatomy.
b. When angiography alone is inadequate to provide optimal vessel or lesion visualization,
intravascular imaging techniques (eg, IVUS or optical coherence tomography) can be used to
facilitatediagnosticortherapeuticperipheralvascularprocedures).
VI.Contrast
A.ModernRadiocontrastAgents
Modern radiocontrast agents are water-soluble compounds carrying tri-iodinate benzene rings. Iodine
attenuatesX-rays,sovesselopacificationisafunctionofcontrastflowandtheconcentrationofiodine.
Older, ionic contrasts carry a carboxyl group and a sodium cation, resulting in two active osmolar
moieties.Theseagentsincludethemonomerdiatrizoate(Hypaque),withthreeiodineatomson1benzene
ring, aswell asthe dimer ioxaglate(Hexabrix),withsixiodineatoms ontwo benzene rings linkedby
amide groups. Newer, nonionic contrasts contain only oneactive osmolar moiety and carrynumerous
hydroxyl groups to improve solubility at the expense of increased viscosity. These agentsinclude the
monomer iohexol (Omnipaque), with three iodine atoms on one benzene ring, as well as the dimer
iodixanol(Visipaque),withsixiodineatomsontwobenzeneringslinkedbyaminegroups(Fig.1.5).
FIGURE1.5 Molecularstructureofseveralcommoncontrastagents.A,Diatrizoate(Hypaque).B,Ioxaglate
(Hexabrix).C,Iohexol(Omnipaque).D,Iodixanol(Visipaque).
B.AdverseEffects
1.CommonAdverseEffects
The mostcommonadverse effects of contrast media include contrast-induced acute kidney injury(CIAKI) and hypersensitivity reactions. CI-AKI is most commonly defined as a 25% increase in serum
creatinine or an increase of ≥0.5 mg/dL within 72 hours of contrast administration, although other
definitionsareemployed.25Althoughtheexactpathophysiologyisunclear,contrastmediaareknownto
bedirectlynephrotoxic.RiskfactorsforCI-AKIincludeioniccontrast,chronickidneydisease,diabetes,
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advancedage,lowbody-massindex,congestiveheartfailure,priorcerebrovasculardisease,priorPCI,
acutecoronarysyndromeatpresentation,dehydration,anemia,hypertension,cardiogenicshock,balloon
pump use, cardiac arrest, and concomitant use of other nephrotoxic agents (eg, nonsteroidal antiinflammatorydrugs,angiotensinconvertingenzymeinhibitors,diuretics).
26–28
a. TheriskofCI-AKIisminimizediftheadministeredcontrastvolumeinmLislessthantwotothree
timesthe patient’sglomerular filtration rate.29In additiontominimization of contrastdosage, the
risk of CI-AKI may also be mitigated by adequate pre-, intra-, and postprocedural intravenous
hydrationtoincreaseurinevolumeandcontrastclearance30aswellasthroughuseoflow-osmolar
contrast agents.All isotonic fluids appear to convey similar protection; fluids containing sodium
bicarbonateprovidenoadvantageovernormalsaline.Noevidenceorcurrentguidelinessupportthe
useofN-acetylcysteinetopreventnephrotoxicity.
b. Hypersensitivityreactionsofvaryingseveritymayoccurasaresultofcontrastexposure.Theseare
mastcell–mediatedreactionswithaspectrumofpresentationsfromsimpleurticariatocomplicated
anaphylactoid reactions including vasodilation, circulatory collapse, angioedema, and
bronchospasm.Riskfactorsforhypersensitivityreactionsincludehighosmolarandioniccontrasts,
atopy, asthma, advanced age, and female gender. Contrast hypersensitivity is not IgE-mediated
anaphylaxis and is entirely unrelated to shellfishallergy, which is an IgE-mediatedreaction to a
tropomyosinproteinantigen.Patientswithpriorcontrasthypersensitivityorastrongatopichistory
maybepremedicatedwithsteroidsandantihistamines.
2.LessCommonAdverseEffects
Severalotherlesscommonadverseeffectshavebeenassociatedwithcontrastexposure.
a. Adelayedhypersensitivitypresentingwithrashandfever24-48hoursafterexposureismediatedby
IgAandIgE;thisself-limitedreactionisparticularlyassociatedwithnonionic,dimericagents.Also,
ahighosmolarloadandsignificantvolumeofcontrastmayexpandtheintravascularspace,leading
to volume overload. Contrast extravasation into a nondistendable space may cause compartment
syndrome. Contrast-related sialadenitis called iodine mumps and iodine-induced hyperthyroidism
arerarelyobserved.
b. CO2 angiography avoids most adverse effects associated with contrast including CI-AKI and
hypersensitivity. Also, the low viscosity ofCO2 permits better filling of collateral branches than
iodinatedcontrast.Extremecautionmustbeusedtopreventaircontamination:giventheconcernfor
airembolism,CO2angiographyisonlyindicatedinthelowerextremitiesandshouldneverbeused
incoronary,thoracic,orcerebralvascularprocedures.
31
VII.PatientSelectionandConsent
A.PatientSelection
Patientselectionforendovascularproceduresisanindividualizedprocessdependentuponconsideration
of multiple factors. A thorough history of symptoms and comorbidities is critical. A comprehensive
physical examination should include assessment of associated pulses and supplied tissues. Initial
diagnosis of lower extremity peripheral artery disease should be performed by ankle-brachial index,
sequential limb pressures, and pulse-volume recording or Doppler waveforms. Further disease
characterizationmaybe performed byDuplex ultrasonography orbyCT,MR,orinvasive angiography
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whenrevascularizationisbeingcontemplated.
1.LowerExtremityIntervention
Appropriatesymptomsincludelifestyle-limitingclaudication,ischemicrestpain,nonhealingulceration,
organgrene.Asymptomaticstenosisofasurgicalgraftdetectedonsurveillanceimagingmayalsobean
indication for intervention.32 Life expectancy and medical comorbidities must also be considered.
Additionally, the likelihood of successful endovascular intervention depends heavily upon the lesion
anatomyincludingaccessibility,length,andcalcification.
2.UpperExtremityIntervention
Nonquantitative criteria similar to those for the lower extremity apply. Further indications for upper
extremity intervention include symptomatic subclavian steal phenomenon due to retrograde vertebral
arteryflowas wellascompromised flowintoaninternal mammarycoronaryarterybypassgraftinthe
settingofischemiccoronarysymptoms.
3.CarotidArteryStenosis
Carotidendarterectomy(CEA)reducesthestrokerateby25%-50%forsymptomaticpatientswith>70%
stenosis by noninvasive imaging or >50% stenosis by invasive angiography
33,34
as well as for
asymptomatic patients with>60% stenosis by noninvasive imaging.
35,36
Both CEA and carotid artery
stenting (CAS)posesimilar compositerisksofstroke,death,andmyocardialinfarctioninsymptomatic
andasymptomaticpatientsandyieldidenticalstrokeriskreductionovertime.
37,38
CASisindicatedasan
alternativetoCEAforsymptomaticorasymptomaticpatients.
39
4.AcuteIschemicStroke
Endovascular therapy is safe and efficacious. Patients with acute ischemic stroke are eligible for
endovasculartherapywithastentretrieverdeviceiftheyhaveaprestrokemodifiedRankinScoreof0-1,
received guideline-driven intravenous tissue plasminogen activator (tPA) with 4.5 hours of symptom
onset,have acuteocclusionofthe internal carotid or proximal middle cerebral artery (M1), National
Institute ofHealth StrokeScale≥6, Albertastroke programearlyCTscore (ASPECTS)≥6, andbegin
proceduraltherapywithin6hoursofsymptomonset.
40
5.RenalArteryStenosis
Forpatients with hemodynamicallysignificantrenalarterystenosis,multisociety guidelinesrecommend
renal artery stenting in the presence of hypertension refractory to maximally tolerated doses of three
antihypertensive agents including a diuretic, inability to tolerate antihypertensive agents, hypertension
before age30 years, and unexplained pulmonary edema orheartfailure.41 Hemodynamic significance
maybedefinedbystenosis≥70%lumendiameter,apeaktranslesionalgradientof≥20mmHg,amean
gradient≥10mmHg,restingfractionalflowreserveof<0.9,orIVUSminimumluminalareaof<7.8mm2.
Patientswithsignificantbilateraldiseaseorasolitarykidneymaybeconsideredforinterventionevenin
theabsenceofclinicalsymptoms,especiallyinthepresenceofchronicrenalfailure.Balloonangioplasty
rather than balloon-expandable stenting may be employed for medically refractory symptoms of
fibromusculardysplasiainthesettingoffavorableanatomy.
6.MesentericArteryStenosis
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