Andersons pediatric cardiology 773
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increasedleftatrialpressure.Mitralstenosis,adysfunctionalleftventricle,aortic
stenosis,coarctationoftheaorta,systemichypertension,patencyofthearterial
duct,andventricularseptaldefectareexamples,andatrialshuntingmay
improvewithtreatmentoftheunderlyingproblem.Asmallamountofleft-torightshuntingisusualinthenewbornandyounginfant14anddefectslessthan6
mmatthisagearelikelynottobeimportantlaterinlife;however,probepatency
oftheovalfossaispresentinuptoone-thirdoftheseindividualsasadults.
CardiacResponsetotheInteratrial
Communication
Inchildhood,theusualhemodynamiccharacteristicsofanuncomplicated
interatrialcommunicationarealargenetleft-to-rightshuntandnormal
pulmonaryarterialpressure.Left-to-rightflowacrossthedefectisphasicand
occurspredominantlyinlateventricularsystoleandearlydiastole.16Numerous
studieshavedocumentedthatmostpatientswithatypicaldefectwithintheoval
fossaalsohaveasmallright-to-leftshunt.15,17Thissmallshuntisnotdetectable
byoximetry,sothereisnosystemicdesaturation,butitcanbedemonstratedby
indicatordilutiontechniques,18contrastechocardiography,19andDoppler
studies.20
Thecontributionofthepulmonaryvenousreturnfromeachlungtothetotal
left-to-rightshuntisunequal.Inatypicallargedefect,80%ofthepulmonary
venousreturnfromtherightlungshuntslefttoright.Thisisincontrastto
between20%and40%ofthepulmonaryvenousreturnfromtheleftlung.14,15,18
Inasinusvenosusdefect,theanomalouslyconnectedrightpulmonaryveins
providemostoftheshuntedblood.Interestingly,thispreferentialshuntingfrom
therightlungdoesnotoccurtoanygreatextentwithanostiumprimum
interatrialcommunication.
Asdiscussed,alargeleft-to-rightshuntattheatriallevelleadstoenlargement
ofboththerightatriumandtherightventricle.21Theleftatrialandleft
ventriculardimensionsareusuallynormalinchildhood,andsystemiccardiac
outputisalmostalwaysnormalinchildren.Incontrast,leftventricularenddiastolicvolumemaybelessthannormal,22andsystemiccardiacoutputhas
beenfoundtobedecreasedinuptohalfthepatientswithanatrialseptaldefect
whoareolderthan18years.23Numerousstudiesinadultshaveshown
significantleftventriculardysfunction,whichmaypersistevenaftersurgical
correction.22,24,25
Despitethegreatlyincreasedflowofbloodtothelungs,pulmonaryarterial
pressureisrarelyelevatedinchildrenandpulmonaryvascularresistanceislow,
frequentlylessthan1Woodunit.26Theincidenceofpulmonaryhypertensionin
patientsyoungerthan20yearsisnomorethan5%inmoststudiesbutincreases
to20%ofthoseagedfrom20to40yearsandisfoundinhalfofthepatients
olderthan40years.3,15,27,28However,severeelevationofresistanceandthe
Eisenmengerreactionareunusualandaredecreasinginfrequencyas
surveillancetechniquesimprove.29,30Thechangesinthepulmonaryvascular
bedatthisstagearesimilarnomatterwhatthecauseofpulmonaryvascular
diseasemaybe,includingapredominanceofintimalfibrosisandendothelial
proliferation,albeitwithlessmedialmuscularhypertrophythanisseenin
patientswithventricularseptaldefects.31TheEisenmengerreactionisnota
uniformresponseinolderage,andsucharesponseissomewhat
idiosyncratic.23,32However,aprogressiveriseinpulmonaryarterypressurewith
worseningcardiopulmonaryfunctionisthenorm(presumablyduetoincreased
shuntingasleftventricularcomplianceworsenswithageandrightventricular
functionworsensasaresult),thusprovidingtherationaleforsurgeryin
childhood.Nonetheless,congestiveheartfailurerarelyoccursbeforethefourth
orfifthdecade.23,33Rarelyanisolateddefectmaycausecongestiveheartfailure
ininfancy;earlysurgerymaybeindicatedinsuchcases,althoughasearchfor
otherprecipitatingfactorsisacrucialpartoftheevaluationoftheseinfants.34–36
Anothercardiacconsequenceofthelong-standingleft-to-rightshuntisthe
occurrenceofatrialarrhythmias,particularlyatrialflutterandfibrillation.They
presumablyresultfromchronicstretchingoftheatriaandoccurmostcommonly
inpatientsolderthan40yearsofage.32,37,38Aswiththeothercomplications
associatedwithinteratrialcommunications,atrialarrhythmiasrarelyoccurin
childhood.Nonetheless,electrophysiologicstudieshavedemonstratedahigh
incidenceofsubclinicaldysfunctionofthesinusnode,alongwithconduction
disturbances,inchildrenpriortooperativeintervention.39–42
ClinicalFindings
Presentation
Milddyspneaonexertionand/oreasyfatigabilityarethemostcommonearly
symptomsofaninteratrialcommunication.Theyarenotusuallypresentduring
infancyorearlychildhood.However,notinfrequently,parentsreportincreased
activityandstaminaafterrepair,and“asymptomatic”adultsfrequentlyreport
improvedexercisetoleranceafterrepair.Aleft-to-rightshuntmayexacerbate
otherconditions,suchasasthmaandotherchronicpulmonarydiseases;again,
earlierthanusualclosureshouldbeconsideredunderthesecircumstances.
Symptomsbecomemuchmorecommoninthefourthorfifthdecadeforreasons
alreadydiscussed.
PhysicalExamination
Thegeneralphysicalexaminationisusuallynormal.Associatednoncardiac
abnormalitiesareuncommoninindividualswithadefectwithintheovalfossaor
asinusvenosusdefect.9Nonetheless,whenthereisadiagnosedsyndrome
knowntobeassociatedwithadefect(e.g.,Noonansyndrome),screening
echocardiographyisindicatedunlessthephysicalfindingsareunequivocally
normal.Skeletalanomaliesoftheforearmandhanddooccuroccasionallyin
associationwithHolt-Oramsyndrome.11Noncardiacanomaliesmuchmore
commonlyaccompanyostiumprimumdefects.NotableexamplesincludeDown
syndrome43andthevisceralanomaliestypicallypresentwithisomerismofthe
atrialappendages.44
Thejugularvenouspulseisusuallynormal,asarebloodpressureand
peripheralarterialpulses.Aleftparasternalliftmaybepresent,butprecordial
motionisoftennormal,especiallyiftheleft-to-rightshuntisnotlarge.Rarely,
thereisasymmetricdevelopmentofthechestwithaprotuberanceofthelower
leftaspectofthethorax,reflectingmoresevereenlargementoftherightheart.
Theheartsoundsarealmostalwaysabnormal.Thefirstsoundatthelowerleft
sternalbordermaybeaccentuatedbecauseofprominentclosureofthetricuspid
valve,45butthiscanbesubtle.Thesecondsoundischaracteristicallywidelyand
fixedlysplit,withlittleornovariationinthewidthofthesplitduringthe
respiratorycycle.Severalreasonsforthelackofrespiratoryvariationinsplitting
