Andersons pediatric cardiology 1259
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MorphologyandMorphogenesisof
IndividualAnomalies
Doubleaorticarchisthetightestformofvascularring.1–10Itreferstothe
presenceoftwoaorticarches,oneoneachsideofthetracheaandesophagus
(Fig.47.3).Boththeleftandrightaorticarchesofthehypotheticalmodel
persist,withoutregressionofanysegment.Anarterialduct,morefrequentlythe
leftthantheright,persists,althoughcaseswithbilateralductshaverarelybeen
described.11Duringfetallife,whenthearterialductispatent,thecomposite
arrangementofthetwoarchesandapatentarterialductproducesa“9”or“6”
configurationatfetalechocardiography.12,13Eachaorticarchgivesriseto
commoncarotidandsubclavianarteries.Inthemajorityofthecaseswithdouble
aorticarch,botharchesarepatent.Usuallytherightarchislargerthantheleft
arch,orlesscommonly,thetwoarchesareequallysized.Theleftarchis
dominantinlessthan20%ofcases.Ingeneral,theapexofthelargerarchis
higherthanthesmallerarch.Occasionally,asegmentofonearchmaybeatretic,
mostlyontheleft.Theatreticsegmentisalmostalwaysdistaltothesubclavian
artery,althoughanatreticstrandmayalsobefoundbetweenthecommoncarotid
andsubclavianarteries.Theatreticsegmentcannotbevisualizedbyanyimaging
modality.Thereforeitisdifficulttodifferentiateadoubleaorticarchwithan
atreticsegmentdistaltotheoriginoftheleftsubclavianarteryfromarightaortic
archwithmirror-imagebranching.Similarly,thedoubleaorticarchwithan
atreticsegmentbetweentheoriginsoftheleftcommoncarotidandleft
subclavianarteriesisdifficulttodifferentiatefromtherightaorticarchwith
aberrantleftsubclavianarteryandleftarterialduct.Inthesettingofadouble
aorticarch,thesubclavianandcommoncarotidarteriesthatarisefromthepatent
andatreticarchesalmostalwaysshowasymmetricarrangement.14Thepatent
partoftheatreticleftaorticarchtendstohaveamoreposteriorpositionthanthe
leftbrachiocephalicarteryarisingfromtherightaorticarch.Aninferiorkinkof
theproximalpartofthecommontrunkforthesubclavianandcommoncarotid
arteriesinthepresenceofadiverticularoutpouchingfromthedescendingaorta
isatelltalesignofthepresenceofanatreticsegmentbetweenthekinkandthe
apexofthediverticulum.15Thedescendingaortaisleftsidedinjustovertwothirdsofpatientswithdoubleaorticarch,beingrightsidedinalmostalltherest
andonlyrarelyoccupyinganeutralmidlineposition.
FIG.47.3 Computedtomogramsshowingacompletedoublearch,are
seenfrombehindandabove(A)andbelow(B).Thedoublearchencircles
thetracheaandesophagus,withtherightarchdominant.Thereformatted
imageinthecoronalplane(C)showsnarrowingofthetracheadueto
compressionbythedominantrightaorticarch(RAA).Thetracheais
slightlybenttotheleft.LCCA,Leftcommoncarotidartery;LPA,left
pulmonaryartery;LSA,leftsubclavianartery;RCCA,rightcommoncarotid
artery;RPA,rightpulmonaryartery;RSA,rightsubclavianartery.
Rightaorticarchwithaberrantleftsubclavianarteryresultsfromabnormal
persistenceoftherightaorticarchandabnormalregressionoftheleftarch
betweentheoriginsoftheleftcommoncarotidandleftsubclavianarteries,the
leftsubclavianarterytakingitsoriginfromthedistalpartoftheleftaorticarch
(Figs.47.4A–Cand47.5A–B).Thedistalremnantoftheleftaorticarch,along
withtheaberrantleftsubclavianartery,producetheretroesophagealcomponent
ofthering.Ithaspreviouslybeendescribedthattheaberrantarterymaycourse
eitherbetweenthetracheaandesophagusorinfrontoftheaorta.1Itiscurrently
usuallybelievedthatarteriesthatdonottakearetroesophagealcourseare
collateralarteries.2Thepersistentarterialductisusuallyleftsided,connecting
theleftpulmonaryarterytothedistalremnantoftheleftaorticarch.1–7,10,16This
combinationisthesecondmostcommontypeofringreportedinmostseries.
Duringfetallife,whenthearterialductiswidelypatent,thiscombinationis
characterizedbyaU-shapedvascularloopthatencirclesthetracheaand
esophagusfrombehind.12,17–20ThisU-shapedloopconsistsoftheascending
aorta,rightaorticarch,distalremnantoftheleftaorticarch,left-sidedarterial
duct,andpulmonarytrunk.Althoughthevascularlooplooksopenanteriorly,a
vascularringiscompletedbytheunderlyingheart.Thisconfigurationchanges
dramaticallywithclosureofthearterialductafterbirth.TheleftlimboftheUshapedloopdisappearswithductalclosure,whilethedistalremnantoftheleft
aorticarchpersistsasadiverticularoutpouching,withtheleftsubclavianartery
arisingfromitsapex.Thediverticularoutpouchingiscalledthediverticulumof
Kommerell.21–24Flowthroughthisdistalremnantisfromtheleft-sidedarterial
ductintothedescendingaortainthefetalcirculationbutswitchesitsdirection
withductalclosuresothattheaberrantleftsubclavianarteryissuppliedfromthe
descendingaortainpostnatalcirculation.Thereforethepresenceofa
diverticulumofKommerellpostnatallyisindicativeofthepresenceofanarterial
ligamentbetweentheapexofthediverticulumandtheleftpulmonaryartery.
Thisvascularringisusuallynotastightasthatproducedbythedoubleaortic
arch.Theseverityoftheesophagealand,toacertainextent,tracheal
compressionvarieswiththesizeofthediverticulum.Whenthistypeofanomaly
isassociatedwithsignificantobstructionofthepulmonaryoutflowtract,asin
tetralogyofFallot,thediverticulumofKommerellmaybeabsentor
inconspicuous.Thisisbecausetheflowofbloodthroughtheleftarterialduct
wasreduced,orevenreversed,duringfetallife.Thereforethedistalremnantof
theleftaorticarchdoesnotpersistasadiverticularoutpouchingafterductal
closure.12Postnatally,anarterialligamentissuspectedwhentheproximalleft
subclavianarteryistetheredinferiorlytowardtheleftpulmonaryartery.The
right-sidedaorticarchwithaberrantoriginoftheleftsubclavianarteryis
occasionallyassociatedwithpersistenceoftherightarterialductorevenabsence
ofarterialductsbilaterally.Thelattercombinationistypicallyseenintetralogy
ofFallotwithpulmonaryatresiaandpulmonaryarterialsupplyviamajor
aortopulmonarycollateralarteries.Thiscombinationformsanincomplete
encirclementaroundtherightsideofthetracheaandesophagus.Therightaortic
archwithaberrantoriginoftheleftbrachiocephalicarteryisrare.25,26Itresults
fromabnormalregressionoftheleftaorticarchproximaltotheoriginoftheleft
commoncarotidartery.Thepersistingarterialductisusuallyleftsided,
completingavascularring.
