Andersons pediatric cardiology 1310
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FIG.49.11 Cross-sectionalechocardiogram,intheshortaxisoftheheart,
showingleftjuxtapositionoftherightatrialappendage(RAA)inthesetting
ofdouble-outletrightventricle(RV).Notethatthemorphologicallyright
appendagehaspassedthroughthetransversesinustoliealongsidethe
morphologicallyleftappendage(LAA).LA,Leftatrium;RA,rightatrium.
FIG.49.12 Subcostalfour-chamberechocardiogramfromthepatient
showninFig.49.11showingthattherightatrialappendage(RAA)is
displacedtotheright.Notethattheroofoftherightatriumisindentedby
thearterialtrunk(arrows),inthiscasethepulmonarytrunk(PT).LA,Left
atrium;LV,leftventricle;RA,rightatrium;RV,rightventricle;SCV,superior
cavalvein.
Sometimesthejuxtapositionisonlypartial,withasmallpouchofright
appendagecontinuingtoprotrudeforwardontherightsideofthearterialtrunk.
Thejuxtapositiondistortstheinternalmorphologyoftheatrialseptum.On
openingtherelativelysmallatrialsurface,theorificeofthejuxtaposed
appendagetendstooccupytheanticipatedsiteoftheovalfossa.Theovalfossa
ismoreslit-like,andisdeviatedposteroinferiorly.Thedistortionoftheright
atriumcanalsoproducepotentialproblemsinatrialredirectionprocedures,
albeitthatnowadaystheseareusuallyperformedonlyaspartofthedouble
switchprocedure,andthisisrarelyundertakeninpatientswithjuxtaposition.
Anotherconsequenceofthejuxtapositionistodistortthelandmarkstothesinus
node.Theterminalgrooveisorientatedinhorizontalratherthanverticalfashion,
andthesinusnodeitselfisdeviatedtowardtheatrioventricularjunction.Much
morerarely,theappendagescanbejuxtaposedtotherightofthearterialpedicle
whenthereistheusualatrialarrangement.Theleftappendageoccupiesthe
transversesinus,comingtoliesuperiorlyrelativetotherightappendage(see
Fig.49.10).Insomecases,rightjuxtapositionisfoundinheartswhentheonly
associatedlesionisanatrialseptaldefect.Inotherinstances,itmayaccompany
exceedinglycomplexlesions.Inthepersonwithamirror-imagedarrangement,
ofcourse,right-sidedjuxtapositionistheexpectedvariant.Itisassociatedwith
thesameconstellationoflesionsasisleft-sidedjuxtapositionintheindividual
withtheusualatrialarrangement.Whenthereisleftjuxtaposition,astraightor
concaverightlowerheartborder,andaprominentbulgingcontouroftheleft
mid-heartborder,areseenonthechestradiograph.Thisisbecausetheright
atrialappendageisnotinitsusualplacebutisdisplacedtotheleft(Fig.49.13).
Thediagnosisisnowreadilymadewithcross-sectionalechocardiography(see
Figs.49.10and49.11),magneticresonanceimaging,orcomputedtomography.
Duringcardiaccatheterization,ifthediagnosishasnotalreadybeenmadeby
echocardiography,thefirstpointertothediagnosismaybethesamplingof
systemicvenousbloodfromtheleftsideoftheheartinalow-pressurezone.If
necessary,selectiveinjectionofcontrastmediumintotheappendagewill
establishthediagnosis.
