Andersons pediatric cardiology 63
Bạn đang xem bản rút gọn của tài liệu. Xem và tải ngay bản đầy đủ của tài liệu tại đây (101.67 KB, 3 trang )
anomissionparticularlybecause,formanyyears,ananteriorpositionofthe
aortawasusedasthecornerstonefordefinitionsof“transposition.”Wepreferto
describearterialvalvarrelationshipsintermsofbothright-leftandanteriorposteriorcoordinates.Suchdescriptioncanbeaccomplishedwithasgreata
degreeofprecisionasisrequired.Agoodsystemistheonethatdescribesaortic
positionindegreesofthearcofacircleconstructedaroundthepulmonary
valve.18Aorticvalvarpositionisdescribedrelativetothepulmonarytrunkin
termsofeightpositionsofacompass,usingthesimpletermsleft,right,anterior,
posterior,andsidebyside,intheirvariouscombinations.Aslongaswe
rememberthatthesedescribeonlyarterialvalvarrelationshipsandconveyno
informationabouteithertheoriginofthearterialtrunksfromtheventricular
mass,orthemorphologyoftheventricularoutflowtracts,wehavenofearof
producingconfusion.
Fromthestanceofpositionsofthearterialtrunks,thepossibilitiesareeither
forthepulmonarytrunktospiralroundtheaortaasitascendsfromthebaseof
theventriclesorforthetwotrunkstoascendinparallelfashion.Onlyrarelyisit
necessaryspecificallytodescribetheserelationships.Spiralingtrunksare
associatedmostfrequentlywithconcordantventriculoarterialconnections,and
paralleltrunkswithdiscordantordouble-outletconnections,butagainthereisno
predictivevalueintheserelationships.Inalmostallhearts,theaorticarch
crossessuperiorlytothebifurcationofthepulmonaryarteries.
Anunexpectedpositionoftheaorticarchisawell-recognizedassociated
anomalyofconditionssuchastetralogyofFallot(seeChapter36)orcommon
arterialtrunk(seeChapter41).Inthisrespect,distinctionshouldbemade
betweenthepositionofthearchandthesideofthedescendingaorta,particularly
whendescribingvascularrings(seeChapter48).Thesideoftheaorticarch
dependsonwhetheritpassestotherightorleftofthetrachea.Thepositionof
thedescendingaortaisdefinedrelativetothevertebralcolumn.
InfundibularMorphology
Theinfundibularregionsarenomoreandnolessthantheoutletcomponentsof
theventricularmass,buttheyhaveprovencontentiousintherealmsof
nomenclature.Forexample,inthepast,thepresenceofbilateralconuseswas
consideredanarbiteroftheventriculoarterialconnectionwhenassociatedwith
double-outletrightventriclebutignoredwheneachgreatarterywithits
completemuscularinfundibulumwassupportedbyitsownventricle.Ifthe
infundibularstructuresarerecognizedforwhattheyare,andtheirmorphology
describedassuch,theyprovidenoproblemsinrecognitionanddescription.19
Themorphologyoftheventricularoutletportionsisvariableforanyheart.
Potentially,eachventriclecanpossessacompletemuscularfunnelasitsoutlet
portion,andtheneacharterialvalvecanbesaidtohaveacomplete
infundibulum.Whenconsideredasawhole,theoutletportionsoftheventricular
massinthesettingofbilateralinfundibulumshavethreediscreteparts(Fig.
1.21).
FIG.1.21 Completeconeofmusculaturesupportingbotharterialvalvesin
thesettingofdouble-outletrightventriclewithbilateralinfundibulumsand
subaorticinterventricularcommunication.Theconeshaveparietalparts,
outlinedinred,posteriorpartsadjacenttotheatrioventricularjunctions,
outlinedinblue,andapartthatdividesthem,outlinedinyellow.Thepart
outlinedinblueistheventriculoinfundibularfold,separatingtheleafletsof
theatrioventricularandarterialvalves,whereasthedividingpart,outlined
inyellow,istheoutletseptum,interposedbetweentheleafletsofthe
arterialvalves.Theanteriorpart,outlinedinred,istheparietalventricular
wall.
Twoofthepartsformtheanteriorandposteriorhalvesofthefunnelsof
myocardiumsupportingthearterialvalves.Theanterior,parietal,partisthefree
anteriorventricularwall.Theposteriorpartistheinnerheartcurvature,a
structurethatseparatestheleafletsofthearterialfromthoseofthe
atrioventricularvalves.Wecallthiscomponenttheventriculoinfundibularfold.
Thethirdpartistheseptumthatseparatesthetwosubarterialoutlets,whichwe
designatetheoutlet,orinfundibular,septum.Thedimensionsoftheoutlet
septumareindependentoftheremainderoftheinfundibularmusculature.
Indeed,itispossible,albeitrarely,forbotharterialvalvestobeseparatedfrom
bothatrioventricularvalvesbytheventriculoinfundibularfoldbutforthearterial
valvestobeinfibrouscontinuitywithoneanotherbecauseoftheabsenceofthe
outletseptum.However,inmosthearts,somepartoftheinfundibular
musculatureiseffaced,sothatfibrouscontinuityoccursbetweentheleafletsof
oneofthearterialandtheatrioventricularvalves.Mostfrequently,itisthe
morphologicallyleftventricularpartoftheventriculoinfundibularfoldthatis
attenuated.Asaresult,thereisfibrouscontinuitybetweentheleafletsofthe
mitralvalveandthearterialvalvesupportedbytheleftventricle.Whetherthe
arterialvalveisaorticorpulmonarywilldependontheventriculoarterial
connectionspresent.Intheusualarrangement,themorphologicallyright
ventricularpartoftheventriculoinfundibularfoldpersists,sothatthereis
tricuspid-arterialvalvardiscontinuity.Dependingontheintegrityoftheoutlet
septum,thereisusuallyacompletelymuscularoutflowtract,orinfundibulum,in
themorphologicallyrightventricle.Whenbothoutletportionsareconnectedto
themorphologicallyrightventricle,mostfrequentlytheventriculoinfundibular
foldpersistsinitsentirety,andthereisdiscontinuitybilaterallybetweenthe
leafletsoftheatrioventricularandarterialvalves.However,manyheartsin
whichbotharterialvalvesareconnectedunequivocallytotherightventricle
havefibrouscontinuitybetweenatleastonearterialvalveandanatrioventricular
valve.Itmakeslittlesensetodenytheoriginofbotharterialtrunksfromthe
rightventricleinthissetting.Thissituationisyetanotherexampleofthe
controversygeneratedwhenonefeatureofcardiacmorphologyisdeterminedon
thebasisofasecond,unrelated,feature.Whenbotharterialtrunkstaketheir
originfromthemorphologicallyleftventricle,thetendencyisfortheretobe
continuitybetweentheleafletsofbotharterialvalvesandbothatrioventricular
valves.Eventhen,insomeinstances,theventriculoinfundibularfoldmaypersist
inpartorinitswhole.
Itisusuallythestateoftheventriculoinfundibularfoldthereforethatisthe
determiningfeatureofinfundibularmorphology.Ignoringtheraresituationof
completeabsenceoftheoutletseptumandconsideringmorphologyfromthe
standpointofthearterialvalves,therearefourpossiblearrangements.First,there
maybeacompletesubpulmonaryinfundibulum,withcontinuitybetweenthe
leafletsoftheaorticandatrioventricularvalves.Second,theremaybea
completesubaorticinfundibulum,withcontinuitybetweenthepulmonaryand
theatrioventricularvalves.Third,theremaybebilateralinfundibulums,with
