Andersons pediatric cardiology 318
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FIG.15.6 Schematicofmorbidityattributedtothehemodynamically
significantductusarteriosus(HSDA)asaconsequenceofpulmonary
overcirculationandsystemichypoperfusion.IVH,Intraventricular
hemorrhage;LCOS,lowcardiacoutputsyndrome;NEC,necrotizing
enterocolitis;PVL,periventricularleukomalacia.(ModifiedfromTeixeiraLS,
McNamaraPJ.Enhancedintensivecarefortheneonatalductusarteriosus.
ActaPaediatr.2006;95[4]:394–403.)
DiagnosisofaHemodynamicallySignificant
ArterialDuct
ClinicalPresentation.
Theclassicalclinicalfeaturesincludeacontinuousmurmur,hyperactive
precordium,boundingpulses,andwidepulsepressure.Morecommonly,a
systolicmurmurisaudiblethatradiateswidelyacrosstheprecordiumandback.
However,inmanyofthosebornpriortoterm,cardiacauscultationis
unremarkable.111Inthefirstweekoflife,despitethepresenceofalargeduct,
typicalclinicalsignsareoftenabsent.Suchasituationiswidelyrecognizedas
thesilentduct,mostlikelyduetocontinuedelevationofpulmonaryvascular
resistance.Surfactant,byassistingthenaturalpostnatalfallinpulmonaryarterial
resistance,hasbeenshowntoalterthetimingofclinicalpresentation,
specifically,byincreasingthevolumeofthesystemic-to-pulmonaryshunt,
whichleadstoanearlierclinicalpresentation.112,113Theexistenceofa
hemodynamicallysignificantbutsilentducthasbeenconfirmedbycardiac
catheterization114,115anddetailedechocardiographicevaluation.116Sucha
situationshouldbesuspectedinasettingofdelayedhypotensionduringthe
secondandthirddays,failureofoxygenation,increasingrequirementsfor
ventilatorsupport,ormetabolicacidosis.Theinfantismorelikelytopresent
withbothsystolicanddiastolichypotensionduetotheinabilityoftheimmature
myocardiumtocompensateforshuntingathighvolumethroughoutthecardiac
cycle.117,118
AncillaryTests.
Althoughnotverysensitive,chestradiographymayshowcardiomegalyand/or
signsofpulmonarycongestion,whereastheelectrocardiogrammayshowsigns
ofleftatrialorventricularenlargement.119,120Thelattermaybemoreusefulfor
theidentificationofsubendocardialischemiasecondarytolowcoronaryarterial
perfusionpressuresinneonateswithalargeduct,121althoughthisassociation
hasnotbeenformallyevaluated.
EchocardiographicConfirmationoftheHemodynamically
SignificantArterialDuct.
Echocardiographyistheprimarytoolforassessmentoftheductusarteriosus.
Echocardiographyconfirmationofductalsignificancepriortotreatmentis
standardofcareinmanyinstitutionsduetotheunreliabilityofclinical
assessment,122adesiretoavoidthesideeffectsofunnecessarymedication,and
thepotentialcomplicationsofindomethacinadministrationtoneonateswithduct
dependentcirculation(left-sidedcongenitalheartdisease[CHD]).The
determinationofductalsignificanceusingechocardiographyinvolves
assessmentofsize,patternsoftransductalflow,systemicand/orend-organ
perfusion,andcharacterizationofthedegreeofvolumeloadingoftheheart.
▪Thesizeoftheductisobtainedfromasuprasternal
short-axisview(Fig.15.7A)usingtwo-dimensional
orcolorDoppler.Atransductaldiameterlessthan1.5
mmisassociatedwithretrogradeorabsentpostductal
aorticdiastolicflow.19Adiameterofmorethan1.5
mmresultedinapositivelikelihoodratioof5.5anda
negativelikelihoodratioof0.22forpredictionofthe
needfortherapeuticintervention.Inaprospective
studyof116neonates,transductaldiameterwasthe
mostaccurateechocardiographicmarkerinpredicting
clinicalandhemodynamicsignificance.123However,
relianceonasinglemeasurementmayleadtoerror
forseveralreasons.First,themeasurementofinternal
ductaldiametermaybedifficult,evenwithcleartwodimensionalimagesandthemeasurementusingcolor
Dopplermaybeinfluencedbygainsettings.Second,
thetransductaldiameterisnotconsistentthroughout,
oftenwithtaperingatthepulmonaryend,andshunt
volumeisdeterminedbythesmallestdiameterwhich
maynotbeaccuratelyidentifieddependingonthe
imagingplaneandbothpatientandoperatorfactors.
Third,thestudiesinvestigatingthepredictivevalueof
ductaldiameterwerelimitedbysmallsamplesizes.
Finally,usinganabsolutecutoffdoesnotconsiderthe
relationshipbetweenductalsizeandinfantsize.Some
studieshaveproposedindexingductalandleft
pulmonaryartery(LPA)diameter,124althoughthis
approachmayalsobequestionable,particularlyin
establishedshunts.Alargeductuswithhigh-volume
left-to-rightshuntmaysignificantlyincreaseflowin
thebranchpulmonaryarteries,andthismayresultin
LPAdilationandreducethevalueofindexing.
