Andersons pediatric cardiology 775
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FIG.29.15 M-moderecordingfromthepatientshowninFig.29.14.There
isabnormalseptalmotionwithanearlydiastolicdiptowardtheleftventicle
(LV)consistentwithrightventricularvolumeoverload.
AlthoughM-modeechocardiographyishelpful,cross-sectional
echocardiographyisthediagnostictechniqueofchoice.However,bewarethe
apicalfour-chamberview,asitmaybeunreliableinevaluationoftheatrial
septum,andartefactualechocardiographicdropoutmaysimulateanatrialseptal
defect.Nonetheless,two-dimensionalechocardiographyprovidesexcellent
visualizationoftheatrialseptuminmultipleotherplanes,withthemostuseful
beingthesubcostalviews.58,59Thesubcostalparacoronalandparasagittalviews,
inparticular,allowsimaginginaplaneperpendiculartotheatrialseptumand
canreliablydefinethesiteandapproximatesizeofthedefect(Figs.29.16and
29.17;Videos29.1to29.3).Pulmonaryveinscanusuallybevisualizedand
anomalousconnectionsidentified,forexampleinthesinusvenosusdefect.60
Thebasicdiagnosticfeatureofasuperiorsinusvenosusdefect,overridingofthe
superiorcavalveinwithabiatrialconnection,canbewelldemonstratedusing
echofromthesubcostalposition(Fig.29.18;Video29.4).61,62Aninferiorsinus
venosusdefectisveryuncommon,andalthoughitissometimesdifficult,this
diagnosiscanalsobemadebyechocardiographyifitisthoughtabout.63The
featuresincludeaposteriorandinferiorlocationofthedefectadjacenttothe
atrialconnectionoftheinferiorcavalveinandanomalousdrainageoftherightsidedpulmonaryveins.Althoughroutinetransthoracicstudiesaregenerally
morethanadequatefordiagnosisinchildren,transesophagealechocardiography
allowssuperbevaluationandvisualizationoftheatrialseptuminpatientswitha
poorstandardechocardiographicwindow(Videos29.5and29.6).64,65Contrast
echocardiographymayprovidesupplementaryinformation,20,66butthisisrarely
necessary.
FIG.29.16 Subcostalparacoronalsectionacrosstheatriums.Thereisa
smallovalfossadefect.LA,Leftatrium;RA,rightatrium;SCV,superior
cavalvein.
FIG.29.17 Color-flowmappingshowsleftatrial(LA)torightatrial(RA)
shuntingacrossthedefectshowinFig.29.16.
FIG.29.18 Subcostalparacoronalsectionthroughtherightatrium(RA)in
apatientwithasuperiorsinusvenosusdefect.Notehowthesuperiorcaval
vein(SCV)overridesthesuperiormarginoftheatrialseptum.LA,Left
atrium;ICV,inferiorcavalvein.
Dopplerechocardiography,includingpulsed-wavestudiesandcolor-flow
mapping,isaninvaluableadjunctintheevaluationofinteratrial
communications.PulsedDopplerdeterminationofthevelocityofthetransatrial
shunthasbeencorrelatedwiththeratioofflowsofthepulmonaryandsystemic
bloodstreams,67andthedegreeofshuntingcanalsobecalculatedusing
echocardiographicandDopplermeasurementsofflowacrosstheright-andleftsidedvalves.68–70Again,however,thesetechniquesarerarelyusedinday-to-day
practice.Conversely,color-flowmappingisextremelyusefulintheevaluationof
atrialshunts.20Flowacrossthedefectcanbeclearlyvisualized(seeFig.29.17)
andmoresubtlevariations,suchasafenestrateddefect,maybecomeapparentas
separateflowjets(Fig.29.19;Videos29.7and29.8).Theimprovedsensitivity
fordemonstratingsmallatrialshuntswithcolorDopplerhasledtothedetection
inahighproportionofsuchdefectsinnewbornsandinfants.71,72Theseshunts
arepresumablycausedbyincompetenceoftheflapoftheovalforamen,are
usuallylessthan6mminsize,andareassociatedwithturbulentflowacrossthe
septum;mostclosewithinthefirstyearoflife.
