Andersons pediatric cardiology 975
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Abstract
Transpositionisbestdefinedasthecombinationofconcordant
atrioventricularanddiscordantventriculoarterialconnections,regardlessof
thespatialorientationofthearterialtrunks.Inthisarrangement,desaturated
bloodinthesystemiccirculationflowsinparallelwithsaturatedbloodin
thepulmonarycirculation.Forsurvivaltobeachieved,theremustbe
mixingbetweenthetwocirculations.Mixingiscommonlyprovidedinthe
formofpersistentpatencyofthearterialduct,andanatriallevel
communication.
Clinicalpresentationisvariabledependingonassociatedanatomicfindings.
Ventricularseptaldefects,leftventricularorsubpulmonaryoutflowtract
obstruction,andabnormalcoronaryarterialanatomyarecommon.
Screeningpracticeshaveimprovedantenatalidentification.Prostaglandin
infusionandballoonatrialseptostomyarecommonlifesavinginterventions
inthenewbornperiodandareimportantconsiderationswhenplanning
delivery.Signsofinadequatemixinginthenewbornincludeacidosis,
hypoxemia,anddecreasedsystemicperfusion.Transthoracic
echocardiographyisusuallyadequatetoachievecompleteunderstandingof
theanatomyandtodeterminetheappropriatemanagementstrategy.
Theneonatalarterialswitchoperation,withaLeComptemaneuver,has
replacedatrialredirectionproceduresastheprocedureofchoiceforsurgical
correction.Operativemortalityforthisprocedureiscurrentlyreportedtobe
approximately2%to5%.Alternativesurgeriesareestablishedforpatients
withmorecomplexanatomy.
Long-termoutcomesofthearterialswitchoperationarefavorable.Ongoing
monitoringisrequired,withparticularattentionpaidtotheneoaorticvalve
androot,thepulmonarytrunk,andthecoronaryarteries.Broader
applicationofimagingmodalities,suchasmagneticresonanceand
computedtomography,isbeingexplored.Thereareconcernsabout
neurodevelopmentaloutcomesinthispopulation,andresearchisongoing.
Keywords
Transposition;Discordantventriculoarterialconnections;Arterialswitch
operation;Balloonatrialseptostomy
Introduction
Thecongenitalmalformationcharacterizedbyoriginofthearterialtrunksfrom
morphologicallyinappropriateventricleshasprobablybeenthesourceofas
muchconfusionandcontroversyasanyothersingletopicinpediatric
cardiology.WhenMatthewBailliedescribedthefirstcase,1hehadnoproblems
withnomenclature,describingtheentityinaccuratefashionasa“singular
malformation.”Sincethen,theentityhasmostusuallybeendescribedsimplyas
transposition.However,ithasbeendefinedinmanydifferentwaysandhasbeen
usedtodescribemanydifferenttypesofcongenitalcardiacmalformations.
Argumentshavecenteredonwhetherthemorphologicarrangementofthe
arterialtrunksshouldbedefinedprimarilyaccordingtotheirventricularorigin
oronthebasisofananteriorlocationoftheaortarelativetothepulmonary
trunk.2,3Suchdisagreementshavebeennonproductive.Intheclinicalsetting,it
istheoriginofthearterialtrunksfromtheventriclesthatisparamountbecause
thisfeaturedeterminesthepatternsofflowofbloodthroughtheheart,
irrespectiveoftherelationshipsofthearterialtrunks.Thecombinationsof
segmentalconnectionsthenproducethevariationsstilldescribedintermsof
“transposition.”Wewilldescribethecombinationtobediscussedinthischapter
simplyastransposition,includingonlythosepatientshavingthespecific
combinationofconcordantatrioventricularanddiscordantventriculoarterial
connections(Fig.37.1).
FIG.37.1 Segmentalcombinationsproducingthelesiondescribedas
transposition,namelyconcordantatrioventricularanddiscordant
ventriculoarterialconnections.Asshown,thelesioncanexistineitherthe
usualatrialarrangement(left)orinthemirror-imagedvariant(right).Note
thattheaortaisusuallyleftsidedwiththemirror-imagedvariant.
