Andersons pediatric cardiology 1174
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foundintheiliacarteriesandintheabdominalandrenalvessels.Stenosisofthe
originofthecarotidandsubclavianarteries,andlessfrequentlytherenaland
mesentericarteries,occursinuptohalfthepatients.Thepulmonarycirculation
isalsoaffected.In20%ofpatients,therearemultiplepulmonaryarterial
stenoses.Thesearemostlyperipheral,beingseenwherethemajorvesselsenter
thelung.Consequently,supravalvaraorticstenosisinmost,butnotall,patients
ispartofamorewidespreadabnormalityofthecardiovascularsysteminvolving
themajorconductingarteries.Histologicfindingsawayfromthesiteofthe
obstructionintheaortashowirregularthickeningandbranchingofmedial
elasticfibers.Thisappearancehasbeendubbedamosaicpattern10or“higgledypiggledy”arteriopathy.17
AorticRegurgitation
Thestenoticaorticvalvecanalsoberegurgitantifthelesionsproducingstenosis
alsopreventthevalvarleafletscoaptingsnuglyduringventriculardiastole.
Isolatedaorticregurgitationismuchrarerthanstenosis.Ifseenasanisolated
findingintheneonatalperiod,refluxthroughanaorto–leftventriculartunnel
shouldbeexcluded.Inthisentity,oneofthevalvarleafletsissuspendedacross
theventriculoarterialjunction,sothatbloodisabletoflowaroundthepartthat
shouldbeattachedwithintheaorticroot(seeChapter51).Regurgitationcanalso
beproducedbyabnormalitiesoftheleaflets,suchasperforationsproducedby
infectiousendocarditisoriatrogenicdamagesubsequenttoballoondilation.
Dilationofthesinutubularjunctionwillalsopreventthevalvarleafletscoapting,
butthisisanacquiredratherthanacongenitalmalformation(Fig.44.11).
FIG.44.11 Aorticroot,viewedfromabove,intheheartfromapatientwith
acquireddilationofthesinutubularjunction,whichmakesitimpossiblefor
thevalvarleafletstocoaptduringventriculardiastoleandresultsingross
aorticregurgitation.
Morphogenesis
Weknowthat,aswasthecaseforthepulmonaryroot(seeChapter42),the
aorticrootdevelopswithintheintermediatecomponentoftheoutflowtract.
Wheninitiallyformed,theoutflowtract,whichissupportedabovethecavityof
thedevelopingrightventricle,hasmyocardialwallstothemarginsofthe
pericardialcavity.Itisatthemarginsofthepericardialcavitythatthecommon
lumenoftheoutflowtractbecomescontinuouswiththecavityoftheaorticsac,
whichgivesrisetothearteriesofthepharyngealarches(seeChapter3).Bythe
timeitbecomespossibletorecognizethepotentialsiteofformationofthe
arterialroots,thewallsofthedistalpartoftheoutflowtracthavebeenreplaced
byadditionofnonmyocardialtissuesfromthesecondheartfield.Growthofa
protrusionfromthedorsalwalloftheaorticsac,developingbetweenoriginsof
thearteriesofthefourthandsixtharches,dividesthedistaloutflowtractintothe
intrapericardialcomponentsofthearterialtrunks.Majoroutflowcushionsare
formedtoseparatethemoreproximalpartsoftheoutflowtract,whichretain
theirmyocardialwalls,intotheaorticandpulmonarychannels.Aswellasthe
majoroutflowcushions,thereareadditionalintercalatedcushionsformedinthe
moredistalpartofthemyocardialoutflowtract.However,thecomponent
containingtheintercalatedcushionsoccupiestheintermediatepartoftheoverall
outflowtract(Fig.44.12A).Itisinthisintermediatecomponentthatthe
positioningoftheintercalatedcushionsrelativetothemarginsofthemajor
cushionsproducestheprimordiumsofthearterialroots(seeFig.44.12B).
