Andersons pediatric cardiology 684

FIG.26.14 Heartandlungsfromapatientwithleftisomerism,
photographedfrombehind.Thevenousreturnfromtheabdomen,apart
fromthatfromtheliver,reachestheheartthroughtheazygosvein,which
runstogetherwiththeright-sidedaorta.

Thepresenceofseparateconnectionofthehepaticveins,whencombinedwith
therelationshipoftheabdominalgreatvesselsrelativetothespine,hadbeen
consideredareliablemeansofdistinguishingnoninvasivelythepresenceofright
andleftisomerism.19Wenowknowthisnottobestrictlyaccurate.Itisdifficult,
ifnotimpossible,todistinguishwithcertaintycasesashavingisomerismsimply
bystudyingtherelationshipsoftheabdominalgreatvesselstothespine.Thisis
nottodetractfromthevalueofthisfeaturewhenusedastheinitialstepinthe
ultrasonographicassessmentofsequentialsegmentalanatomy.Knowledgeofthe
overallconnectionsofthepulmonaryveins,theinferiorcavalvein,andthe
drainageofthehepaticveinstotheatriums,alongwiththearrangementofthe
coronarysinus,nonetheless,isamoreaccuratemeansofdistinguishingbetween
therightandleftformsofisomerism.Bilateralconnectionsofsuperiorcaval
veinstotheroofsoftheright-andleft-sidedatriums,however,arefrequentin
eithersetting.Inthosewithisomericleftappendages,theseconnectionsare
anomalousoneachside.Inthosewithisomericrightatrialappendages,in
contrast,theyareanatomicallynormal,witheachcavalveinappropriately


relatedtoaterminalcrest(Fig.26.15),andwithsinusnodespresent
subepicardiallyinthebilateralterminalgrooves.Thedrainageoftheveinsfrom
theheartitselfisalsoabnormalinbothrightandleftisomerism.Thisisnomore
thantobeexpectedinrightisomerismsince,intheuniversalabsenceofthe
coronarysinus,thereisnotransversechannelwithintheatrioventriculargroove
tocollectthevenousreturnfromtheheart.Thevariabilityinterminationofthe
individualcardiacveinsissurprising.Theveinscanterminatedirectly,takea
crookedcourseforashortdistancealongtheatrioventriculargroove,ortraverse

theatrialwallforsomedistancebeforedrainingintotheatriumwellawayfrom
theatrioventriculargroove,oftenadjacenttotheopeningofapulmonaryor
systemicvein(Fig.26.16).Suchdirect,crooked,ordistantvenousterminations
arealsotobefoundinheartswithisomericleftappendages,butacoronarysinus
receivingallthecoronaryvenousreturnismorefrequentincaseswithleft
isomerism.27

FIG.26.15 Internalaspectoftheright-sided(A)andleft-sided(B)atrial
chambersfromapatientwithisomericrightatrialappendages.The
presenceofterminalcrestsbilaterallyisobvious.


FIG.26.16 Inferiorsurfaceofaheartwithisomericatrialappendages
illustratingtheconceptofdirect,crooked,anddistantreturnofcoronary
venousdrainagewhenthecoronarysinusisabsent.

AtrialSeptum
Althoughtheextentofatrialseptaldeficiencyfailspositivelytodiscriminate
betweenpatientshavingisomericrightorleftatrialappendages,theseptum
tendstobebetterformedinthosewithleftisomerism.Inthosewithrightatrial
appendagesbilaterally,mostfrequentlythereissimplyastrandofatrialtissue
thatspansacommonatrialcavity.Itisraretofindtheatrialseptumcompletely
lacking,butinmostcasesthereis,effectively,acommonatrium.Inaboutonefourthofcases,theseptumiswellformedsuperiorlyinassociationwithan
atrioventricularseptaldefect,whileveryrarelytheseptumcanbeintactorthe
ovalforamenbeprobepatent.Aneffectivelycommonatriumistobeexpected
inabouthalfofcaseswithleftisomerism.Anatrioventricularseptaldefectis
alsopresentinnearlyhalf,whiletheseptumcanbevirtuallyintactinnearlyonefifth.