Andersons pediatric cardiology 1293
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FIG.48.10 Reanalyzedcomputedtomographicdatasetfromthepatient
showninFig.48.9Busingvirtualcardiacdissectiontechnique.(A)Frontal
viewshowsexternalmorphology.(B)Short-axisviewasseenfrombelow
showsarrangementofthevesselsfrominside.Thechannelsupplyingthe
leftpulmonaryarteryunequivocallyarisesdistaltothebrachiocephalic
artery,makingitmorelikelytorepresentaremodeledleft-sidedarterial
duct,moresosinceitsuppliesthediscontinuousleftpulmonaryartery.
AnomalousOriginofaPulmonaryArteryFrom
theAscendingAorta
Otherinvestigatorshaveinvokedpersistenceofthefiftharcharterytoexplain
anomalousoriginoftherightorleftpulmonaryarterydirectlyfromthe
ascendingaorta.29,34,55,63Suchinterpretationsdonotreflectcurrentknowledge
concerningthedevelopmentoftheintrapericardialcomponentsofthearterial
trunks.Therightandleftpulmonaryarteriesdevelopwithinthepharyngeal
mesenchyme,takingtheiroriginsfromthesixtharcharteriesastheyexitfrom
theflooroftheaorticsac.Theywouldhavenodirectconnectionwithafifth
archarteryshouldsuchanarterybepresent.Itisunequalseparationoftheaortic
sacthatresultsinanomalousconnectionofeitheroftherightorleftpulmonary
arterytotheascendingaortaratherthanretainingitsconnectionwiththe
pulmonarytrunk.9
Thedubiousnatureoftheevidenceofferedforpersistenceofapresumed
arteryofthefiftharchisfurtherevidencedbyreanalysisoftheinterpretations
offeredforcaseshavingbothanomalousoriginofapulmonaryarteryfromthe
ascendingaortaandadouble-barreledaorta.Inthedescribedinstancesofthe
casesofwhichweareaware,itwastheleftpulmonaryarterythattookitsorigin
fromtheascendingaorta.Thedouble-barreledaortawasitselfleft-sided34,55in
twoofthereportedcasesandright-sidedintheother.29Theserareanatomic
aberrationscanbeexplainedonlyonthebasisofpersistenceofthearteryofthe
fiftharchifthepurportedarteryiseitherbilateral29orisitselfduplicatedonthe
leftside.34,55Sincetheexistenceofasolitaryfiftharcharteryisindoubt,
suggestionsforexistenceofdualorbilateralfiftharcharteriesareimplausible.
Farbetterexplanationsareavailableonthebasisofpersistenceofcollateral
channelsforthedouble-barreledaortaandunequalseparationofaorticsacfor
theanomalousoriginofthepulmonaryarteryfromtheascendingaorta.
UnusualFormsofSystemic-to-Pulmonary
ArterialConnections
Thelackofanyconnectionofthepulmonaryarterieswithachannelthat
continuestosupplythedescendingthoracicaortahasledsomeauthorstoargue
thatthechannelitselfisthefifth,ratherthanthesixth,archartery.These
arrangements,however,canequallywellbeinterpretedonthebasisofa
commonarterialtrunkwithpulmonarydominanceandinterruptionoftheaortic
arch,withthevesselinquestionindeedrepresentingthepersistentarterialduct
(Fig.48.11A).71Inanotherpatient,whohadaorticatresiawithinterruptionof
theaortabeyondbothcarotidarteriesandwithaberrantretroesophagealoriginof
therightsubclavianartery,theauthorsinterpretedthechannelconnectingthe
rightpulmonaryarterytothediminutiveascendingaortaasrepresentingthe
persistingarteryofthefiftharch.Thechannelinquestion,nonetheless,takesits
originfromaright-sidedbrachiocephalicarteryandconnectsdirectlytotheright
pulmonaryartery.Onthebasisofprobabilities,therefore,itismorelikelythat
thevesselrepresentstheright-sidedarterialduct(seeFig.48.10B).23We
acknowledge,however,thatinanotherreportimplicatingthefiftharchartery,
theanatomyissounusualastodefylogicalinterpretationbasedonourcurrent
understandingofcardiacdevelopment.72
FIG.48.11 Twocasesreportedintheliteratureasrepresenting
persistenceofthearteryofthefifthpharyngealarch.(A)Inthis
malformation,thechannelconnectingtothedescendingaortawasthus
interpretedasfiftharchartery.71(B)Inthismalformationthechannel
connectingthediminutiveascendingaortatotherightpulmonaryartery
wasinterpretedasfiftharchartery.23Asthisillustrationshows,inboth
instancesthechannelscouldjustaswell,ifnotmorelikely,have
representedthepersistentlypatentarterialduct.
AbnormalOriginofBrachiocephalicArteries
Manyinvestigatorshaveinterpretedabnormalarrangementsoftheoriginofthe
brachiocephalicarteriesfromtheascendingaortaortheaorticarchonthebasis
ofpersistenceoffiftharcharteries(Table48.3).77–107Aswehavenowshown,
thearterieswithinthepharyngealarchesarisingfromtheaorticsacundergo
extensiveremodelingduringtheembryonicperiodbeforeattainingtheirfinal
configuration(Figs.48.3to48.6),withthehornsoftheaorticsacitself
providingtheconfluenceofthearteriesofthethirdandfourtharches.Variations
inthepatternofbranchingoftheextrapericardialarteriesfromtheaorticarch,
