Andersons pediatric cardiology 1326
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arterialsupplyfrombronchialornonbronchialsystemicarteriesintothePAVM
sacandduringpregnancy.90Otherlesscommonpresentationsorcomplications
ofPAVMsincludepleuriticchestpainin10%ofpatientswithPAVMs,CHF
secondarytohighoutputfromlargeextrapulmonaryAVMs(primarily
intrahepatic)andpolycythemiasecondarytohypoxemia.91Chronichypoxemia
stimulatessecondaryerythrocytosis(polycythemia)tomaintainarterialoxygen
content.AfterembolizationofPAVM,theerythrocytosisresponseabateswitha
fallinhemoglobinlevelwithinmonths.92Inaddition,PAVMpatientshave
impairedCO2clearanceresultinginabnormallyhighventilatorydriveand
increasedminuteventilationonexercise.PAVMspatientshavehighcardiac
outputatrestandwithexercise.Duringexercise,thesepatientsuseincreased
strokevolume,improvedoxygendeliverysecondarytoincreasedhemoglobin
andredcellmass,modifiedironhandling,andexuberantposturaltachycardiaas
plausiblemechanismsforadaptiveexercisetolerance.93
Investigations
TheevaluationofPAVMisoftensoughtfortheinvestigationofrespiratory
symptomssuchasdyspneaorhemoptysis,suspectedright-to-leftshuntingin
patientswithcyanosisorHHT,orcerebralabscessand/orunexplainedembolic
stroke.Aroundoroval-shapedmassornodulemayoccasionallybeseenon
chestradiograph;however,thePAVMneedstobefairlylargetobedetectedin
thismanner,andmany(10%to40%)arenotdetected,makingroutinescreening
bychestradiographinsensitive.47Severalnoninvasivemethodstoassessand
quantifyright-to-leftshuntingacrossthePAVMsincludemeasuringarterialPaO2
on100%oxygenandperfusionscansusingtechnetium-labeledalbumin
macroaggregates.TransthoracicCEisrecommendedbytheinternationalHHT
guidelinesasinitialscreeningtoolforPAVMs,withasensitivityof100%and
thespecificityof67%to91%.65CEwithagitatedsalinedetectsintrapulmonary
shuntingwiththeuseofnoninvasiveultrasoundtovisualizedelayedappearance
ofmicrobubblesintheleftsideoftheheartafterthreetofourcardiaccycles.In
contrast,themicrobubblesarevisualizedwithinonetotwocardiaccyclesin
patientswithintracardiacshuntsuchaspatentforamenovaleoranatrialseptal
defect.ChestCTscan,althoughnotpartofthePAVMsscreeningprocess,is
widelyconsideredthegoldstandarddiagnostictoolforfurtherevaluationof
patientswithahighsuspicionofPAVMstodemonstratesize,location,and
extentofPAVMpriortotherapy.ThehigherresolutionofCTispreferredto
MRI.Pulmonaryangiographyisnolongerconsiderednecessaryfordiagnostic
purposesaloneandissolelyreservedfortherapeuticpurposesafterdiagnosisis
established.47
Management
PercutaneousTCEisthegoldstandardforthetreatmentofPAVMsduetoits
effectivenessinreducingparadoxicalembolismanditsassociatedcomplications.
Severalserieshavedemonstratedreductioninright-to-leftshunting,
improvementinoxygenation,reductioninstrokes,migraines,reduced
erythrocytosis,improvedexercisetolerance,andpreventionoflung
hemorrhage.47,82,94,95Therefore,regardlessofsymptoms,anyPAVMswith
feedingarterygreaterthan3mmindiameterasdetectedbyCTaregenerally
recommendedforTCE.Duringtheprocedure,ifadditionalsmallerPAVMsare
found,thegoalistooccludeasmanyfeedingarteriesastechnicallyfeasible,
eventhosethatdonotconformtothe“3mmrule.”82,96Afterobtainingfemoral
venousaccess,antibioticprophylaxisisadministeredpriortoPAVM
embolization.Thecatheterisadvancedtobothpulmonaryarteries,andbaseline
angiogramsprovideanoverviewofthenumberanddistributionofPAVMs.
EmbolizationofPAVMsisperformedbytargetingthesupplyingarteryjust
proximaltotheaneurysmalsac(seeFig.50.8).Acoaxialcathetersystem
involvinganouterguidecatheterforstabilizationandaninnercatheterfor
deploymentofthedeviceiscommonlyused(seeFigs.50.8and50.10).
Postdeploymentangiogramsarenecessarytoensureallpossiblesourcearteries
totheaneurysmalsacareoccluded(seeFigs.50.10and50.11).95Technical
advanceswiththeuseofmicrocatheters,coils,andmicrovascularplugshave
allowedocclusionofevensmallfeederarteriessuccessfully(seeFig.50.11).
FIG.50.10 A55-year-oldmanhadahistoryoflivercirrhosisandsevere
hypoxemia.RightandleftpulmonaryarteryangiogramsandCTscan(A–
D)demonstrateintrapulmonaryvasculardilation(arrows)consistentwith
hepatopulmonarysyndrome.
