Andersons pediatric cardiology 850
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FIG.32.33 Left,Three-dimensionalcomputedtomographicreconstruction
viewedinarightanteriorobliqueprojectionwiththefreewalloftheright
ventricleremoved,demonstratingaperimembranouscentralventricular
septaldefectwithresultingaorticandtricuspidvalvefibrouscontinuityand
deficiencyoftheposteriorcaudallimboftheseptomarginaltrabeculation.
Thesupraventricularcrestretainsitspositionwiththelimbsofthe
septomarginaltrabeculation.Middle,Inasimilarprojectionthedefect
extendsfromtheperimembranouscentralregionsoastoopentothe
outlet,nowwithdivorceofthesupraventricularcrestfromwithinthelimbs
oftheseptomarginaltrabeculation,withresultinganteriordeviationofthe
muscularsubpulmonaryoutletseptum.Right,Inthesameprojectionthe
defectisdemonstratedtoextendfromjustbelowthepulmonaryvalve
towardthecentralregion,nowwithbothpulmonaryandaorticvalveaswell
astricuspidandaorticvalvefibrouscontinuity.Thedefectisbothdoubly
committedandjuxtaarterialaswellasperimembranous.
FIG.32.34 Three-dimensionalprintedmodeldemonstratingalarge-sized
perimembranousventricularseptaldefect(PVSD)openingtotheinlet
underneaththeseptalleafletofthetricuspidvalve(TV).Additionally,there
aremultipleapicalmusculardefects(MVSD,outlinedbyhashedcircle).
RV,Rightventricle.(CourtesyPuneetBhatla,DivisionofPediatric
Cardiology,NewYorkUniversityLangoneMedicalCenter.)
CardiacCatheterization
Priortotheadvancesmadeincross-sectionalechocardiography,catheterization
wasanessentialpartoftheassessmentofpatientswithlargerestrictiveand
unrestrictivedefects.Itmadepossiblethemeasurementofintracardiacpressures,
particularlythepulmonaryarterialpressure,alongwithquantificationofthe
flowofbloodtothelungs.Thisinformationmadeitpossibletocalculatethe
pulmonaryvascularresistance.Inaddition,thetechniqueprovidesconfirmation
oftheinterventricularlocationofthedefectbythedetectionofastep-upin
saturationofoxygenattheventricularlevel,orbyvisualizationofthepassageof
thecatheterfromrighttoleftventricleortotheaorta.Ifthedefectismodified
byabnormalattachmentsoftheleafletsofthetricuspidvalve,suchthattheshunt
isfromleftventricletorightatrium,thenthestep-upinsaturationofoxygenis
detectedintherightatrium.Thisisalsofoundwhenaventricularseptaldefect
coexistswithanatrialseptaldefect,orwhenthereisanatrioventricularseptal
defect.Cardiaccatheterizationhasprovidedfurtherinformationaboutthe
associateddefects.Passageofthecatheterfromthepulmonarytrunktothe
descendingaorta,forexample,indicatesthepresenceofacommunication
betweenthesetwoarteries,usuallyapatentarterialduct.
Thefindingsatcatheterizationreflectthepathophysiology.Unrestrictive
defectswithahighpulmonarybloodflowhavesimilarpressuresinrightandleft
ventricles.Withanunobstructedrightventricularoutflowtractandalow
pulmonaryvascularresistance,thepulmonaryarterialsystolicpressurewillbe
similartothatintheaorta.Thediastolicandmeanpulmonaryarterialpressures
willbelowerthanaorticpressures.Insuchcases,ahighflowtothelungswillbe
measuredoximetricallyor,inthepast,bydyedilutioncurves.Inlargebut
restrictivedefects,therightventricularandpulmonaryarterialpressureswillbe
lowerthanthoseintheleftventricleandaorta.Themaincurrentindicationfor
cardiaccatheterizationotherthanforinterventionalclosureofthedefectisto
establishbeyonddoubtthatapatientsuspectedtohavepulmonaryvascular
diseasedoesnothaveanelevationofpulmonaryvascularresistancesogreatas
torenderthepatientinoperable.
Angiocardiography
Althoughacasecanstillbemadeforperformingcatheterizationinordertotake
measurementsandcalculateshuntsandpressures,itisnowrarelynecessaryto
performangiography.Inthepastthetechniquewasdirectedtoanatomic
delineationofthedefectitselfandtothediagnosisorexclusionofassociated
abnormalities.Leftventricularangiocardiogramswerebestforanatomic
diagnosis.Ifstillperformed,itisbesttochooseanaxialobliqueprojection.51–53
Thelong-axisviewisbestfordemonstratingthedifferenttypesof
perimembranousdefects(Fig.32.35).54Doublycommittedjuxtaarterialdefects
willalsobeshownonthisview,butdemonstrationofthelackofinfundibular
musculatureseparatingthedefectfromthehingepointsoftheleafletsofthe
pulmonaryvalverequiresarightanteriorobliqueprojection(Fig.32.36).The
long-axisviewisagainbestfordemonstratingmusculardefectsintheapical
trabecularseptum(Fig.32.37).Amusculardefectbetweentheinletsisclearly
demonstratedinthefour-chamberview,whereasamusculardefectbetweenthe
outletsisprofiledinlongaxialprojection(Fig.32.38).Ifthereisdoubtaboutthe
siteofthedefect,thelong-axisviewishelpfulbecausedefectsopeningtothe
rightventricularinletappearbehindthelineoftheanteriorportionofthe
muscularseptum.Ifangiographyisperformed,carefulexaminationofthe
angiocardiogramsshouldalwaysbeundertakentoexcludemitralregurgitation.
Inpatientswithpulmonaryhypertension,apersistentarterialductmustalways
beexcluded.Thisisfrequentlypossibleontheaxialobliqueleftventricular
injection.Whenthisisnotthecaseandechocardiographyhasnotresolvedthe
issues,aortographymustbeperformed.Asimilarapproachmayalsobe
necessarytoexcludeassociatedaorticcoarctation.Retrogradeaortographyis
importantwhenaorticregurgitationissuspected.Rightventricularangiography
isindicatedwhenobstructionintherightventricularoutflowtractisfoundon
cardiaccatheterization.Thisisbestperformedinthe45-degreehead-upposition
usinganteroposteriorandlateralprojections.
