Andersons pediatric cardiology 2274
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Recently,researchhasbeenevaluatingwhetherscreeningforcongenitalheart
defectsispossibleinthefirsttrimester.First-trimesterscreeninghasbeenshown
toreliablyvisualizesingleventriclelesionsaswellastranspositionofthegreat
arteries.22SomestudieshavesuggestedthatthevastmajorityofmajorCHDs
canbedetectedduringafirst-trimesterultrasoundifperformedbyan
experiencedfetalsonographerandobstetricianasearlyas11to13weeks'
gestation.23,24Analysisoffirst-trimesterscreeningshowsthatcardiac
abnormalitiesidentifiedinthefirsttrimesterweremorecommonlyassociated
withchromosomalabnormalities(50%to73%)comparedto17%to21%in
second-trimesterscreening.22,25Someauthorssuggestthatearlyprenatal
diagnosismayalterthenaturaloutcomeofpregnancieswithCHDasitmay
increaseearlyterminationoffirst-trimesterpregnancies.However,caution
shouldbeexercisedwhencounselingfamiliesinthefirsttrimesterasitisnot
alwayspossibletodetectcardiacabnormalitiesinenoughdetailtoprovide
accurateestimationofthenaturalhistoryofthesuspectedlesion.Furthermore,
somecardiaclesionsmaynotbefullydiagnosableinearlypregnancy,andfirsttrimesterscreeningshouldnotreplacesecond-trimesterscreening.22
Extracardiacandchromosomalabnormalitiesarefrequentlypresentwhen
CHDisdiagnosedprenatally.Forthatreason,whenCHDisdiagnosed
prenatally,considerationshouldbegiventochromosomaltestingandsecondary
anatomicscreeningifthesehavenotalreadybeencompleted(Table89.2).26
Table89.2
GeneticandExtracardiacAnomaliesWhenThereIsaPrenatalDiagnosisofCongenitalHeart
Disease
CongenitalHeartDisease
AVSD
VSD
ASD
TOF
DORV
HLHS
Truncusarteriosus
Transpositionofthegreatarteries
Coarctationoftheaorta
Tricuspidatresia
Ebsteinanomaly
Aorticstenosis
Pulmonarystenosis/atresia
ChromosomalAnomaly(%)
35–47
37–48
1–3
27
12–45
4–10
14–33
0–3
21–30
2–9
0–3
1–15
4–5
ExtracardiacAnomaly(%)
30–50
30–37
16
25–30
19–20
1
15–21
15–26
12–20
15–34
6
13
20–26
ASD,Atrialseptaldefect;AVSD,atrioventricularseptaldefect;DORV,double-outletrightventricle;
HLHS,hypoplasticleftheartsyndrome;TOF,tetralogyofFallot;VSD,ventricularseptaldefect.
FromGembruchU,GeipelA.Indicationsforfetalechocardiography:Screeninginlow-andhighrishpopulations.In:YagelS,etal,eds.FetalCardiology:Embryology,Genetics,Physiology,
EchocardiographicEvaluation,DiagnosisandPerinatalManagementofCardiacDiseases,ed2.
CRCPressTaylor&FrancisGroup;2008.
PulseOximetryScreening
ThecalculatedprevalenceofcriticalCHD(requiringinterventioninthefirst
yearoflife)variesfromstudytostudy,butbasedonmostrecentestimatesis
approximately2infantsper1000livebirths,withanoverallprevalenceofany
typeofCHDof9infantsper1000births.27Earlydiagnosis,particularlyof
criticalCHD,canpreventsignificantmorbidityandmortality.Newbornswith
criticalCHDcanhaveprofoundandrapiddeteriorationinclinicalstatusinthe
firstdaysorweeksoflife,usuallyrelatedtoclosureoftheductusarteriosusand
physiologicchangesinpulmonaryvascularresistance.Identificationofthese
newbornspriortohospitaldischarge,andpriortothedevelopmentofsignificant
hemodynamiccompromise,canallowfortimelyinterventionandmedical
managementsuchasprostaglandintherapytomaintainductalpatency.The
relativelyhighprevalencecombinedwithaperiodoftimewherecriticalCHD
canbediagnosedpriortoclinicaldeteriorationmakescriticalCHDanideal
subjectforpopulation-basedscreening.
Earlystudiesevaluatingtheuseofpulseoximetryinneonatesdemonstrated
thatlower-extremityoxygensaturationininfantswithcriticalCHDwaslower
thanage-matchedcontrolsubjectswithoutcriticalCHD.28Indeterminingthe
mosteffectivescreeningstrategy,sensitivityandspecificityshouldbe
maximized.False-positiveresultscanbeapublichealthconcernastheyrequire
subsequenttesting,whichinsomesettingsmaydelayhospitaldischargeofthe
infantorrequiretransfertoanotherinstitution,resultinginaddedfamilial
anxiety,stress,andcost.However,increasingspecificityattheexpenseof
sensitivitywillincreasethefalse-negativerate,possiblyresultinginaless
effectivescreeningregimenoverall.TheAmericanHeartAssociationand
AmericanAcademyofPediatricsconvenedawritinggrouptocomposea
scientificstatementin2009toevaluatetheevidenceontheroutineuseofpulse
oximetryinnewbornstodetectcriticalCHD.Theyanalyzedtenstudies,
includingover123,000infantstotal.Overall,thesensitivityofpulseoximetry
screeningforcriticalCHDrangedfrom0%to100%withspecificityranging
from95.5%to100%.False-positivescreenswerefoundinameanof0.9%of
infantswithadecreaseinthefalse-positiverateto0.04%after24hours.The
writinggroupsuggestedthatasinglelower-extremitypulseoximetryreadingat
anagegreaterthan24hourswithathresholdof95%orgreaterwasthemost
