Andersons pediatric cardiology 776
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FIG.29.19 Color-flowmappinginapatientwithafenestratedovalfossa.
Notethetwodistinctjetsofleftatrial(LA)torightatrial(RA)shunting.SCV,
Superiorcavalvein.
MagneticResonanceImaging
Magneticresonanceimaging(MRI)candemonstrateinteratrial
communications,73butitismostcommonlyusedwhenechocardiographic
evaluationisincomplete.74Itmaybeparticularlyusefultodelineatethecourse
andconnectionofthepulmonaryveinswhentheyarenotwellseenby
echocardiography,usuallyinolderpatients.MRItechniquescanbeusedto
measurepulmonarybloodflowandtheQP:QSratio;however,giventhatsuch
measuresarerarelyusedtodeterminetheneedforoperation,theindicationsfor
themarerare.Consequentlythevastmajorityofpatientsshouldbeabletobe
managedwithoutMRIbeingperformed.
CardiacCatheterization
Similarly,echocardiographyandDopplerstudieshavenowlargelysupplanted
“diagnostic”invasivestudiesinpatientswithatrialseptaldefects.Whenthereis
anatomicuncertainty,MRIwillnowusuallybeperformed,makingtheneedfor
diagnosticcardiaccatheterizationevenlesslikely.Theuseofinvasive
assessmentisalmostentirelyrestrictedtotheevaluationofpulmonaryartery
pressure,resistance,andthediagnosisofassociatedabnormalities.
Whilediagnosticcardiaccatheterizationisnowararity,transcatheterclosure
ofovalfossadefectshasbecomeoneofthecommonestinterventional
proceduresinmostcardiaccatheterizationlaboratories.
CourseandPrognosis
Anisolatedinteratrialcommunication,evenalargeone,isusuallywelltolerated
formanyyears,28andsymptomsareusuallyminimalorabsentduringinfancy
andchildhood.Thisisbecausetherightventricleiswelladaptedtopurevolume
overload,75andsecondarypulmonaryhypertensionisusuallyalate
complication.
Symptomstendtooccurearlierandtobemoreseverewhenthereisan
associatedanomaly,particularlyonethattendstoimpedeleftatrialemptying.
Examplesincludeobstructionoftheleftventricularoutflowtract,coarctationof
theaorta,primaryleftventricularmyocardialdisease,andmitralstenosis.Inthis
respect,Lutembachersyndromereferstothecombinationofanatrialseptal
defectandmitralstenosis.Itnowseemstobequiteuncommon,probably
becauseofadecreasingincidenceofrheumaticheartdiseaseandthetrend
towardearlyclosureofatrialseptaldefects.Nonobstructiveassociated
anomaliesmayalsoleadtoearlycongestiveheartfailure.Infantswithboth
interatrialandinterventricularcommunicationsorapatentarterialductarelikely
tobesymptomaticbecauseatrialshuntingacrossevenasmalldefectmaybe
greatlyaugmentedbytheincreasedleftatrialpreloadcausedbytheassociated
lesion.
Ifimpedancetoleftatrialemptyingismarkedlyincreasedandispresent
beforethepulmonaryvascularbedhashadanopportunitytomature,the
pulmonaryvascularresistancemaynotfallandpulmonaryhypertensionmay
persist.Thisissometimesseenininfantswithsevereleftheartobstructive
lesions(e.g.,criticalaorticstenosisormultilevelleftheartobstructionsuchas
Shonesyndrome).Underthesecircumstancessignsofsevereandrapidly
progressivecongestiveheartfailuremayoccur.Thesepatientscanbe
particularlydifficulttomanage,aspulmonaryvasodilatorsmaybehazardousif
leftheartcomplianceisabnormal.Indeed,everyeffortshouldbemadeto
improvelefthearthemodynamicspriortosuchtherapy.
Occasionallyinfantswithisolatedanduncomplicatedatrialseptaldefectsmay
besymptomaticandexperiencecongestiveheartfailure.34–36Itisnotclearhow
theseinfantsdifferfromthosethatareasymptomatic,althoughithasbeen
postulatedthatasubtlealterationinleftventricularcomplianceoran
abnormalityofthemitralvalvarapparatusisthedriverforsuchalargeleft-to-
