Andersons pediatric cardiology 1179
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Moderate
Severe
3.0–3.9
>4.0
20–39
>40
ModifiedfromNishimuraRA,OttoCM,BonowRO,etal.2014AHA/ACCguidelineforthe
managementofpatientswithvalvularheartdisease:areportoftheAmericanCollegeof
Cardiology/AmericanHeartAssociationTaskForceonPracticeGuidelines.JAmCollCardiol.
2014;63(22):e57–e185.
Alternatively,echocardiographycanbeusedtoestimatetheareaoftheorifice
ofthestenoticvalve,whichisalsousedtocategorizetheseverityofstenosis.In
thepediatricandyoungadultpopulation,absolutepressuregradientsare
preferredovervalveorificeareainassessingthedegreeofaorticstenosis,
primarilyduetopracticallimitationswiththemeasurementsandcalculations
involvedinvalveorificeareathataremagnifiedinthepediatricpopulation.
Athoroughevaluationbyechocardiographyofassociatedcardiacdefectsis
important,especiallyintheneonateandinfantwithsevereaorticstenosis.
Associateddefectsincludeendocardialfibroelastosis,mitralvalveabnormalities,
coarctationoftheaorta,andventricularseptaldefects(Fig.44.18).These
associateddefectscanimpactbothtimingandtypeofintervention.Duetorisk
forprogressivedilationoftheascendingaorta,individualsshouldalsohave
serialechocardiogramstotrackthedimensionsoftheiraortaandcomparethe
resultstoage-matchedcontrols.
FIG.44.18 Thispatienthascriticalaorticstenosis,producedbya
unicommissuralvalve.Thereisborderlineleftventricularvolume,and
endocardialfibroelastosischangesarenoted.LA,Leftatrium;LV,left
ventricle;RV,rightventricle.
MagneticResonanceImaging
Theroleofcardiacmagneticresonanceimagingintheassessmentofaortic
stenosisistoidentifythelevelofobstruction,determineitsmechanism,assess
theascendingaorticdimension,andevaluateforassociatedaorticinsufficiency.
Thiscanbeausefultool,particularlyinolderpatients,ifechocardiographic
evaluationissuboptimalduetodifficultimagingwindows.Theuseofcardiac
magneticresonancealsocanprovideanaccurateevaluationformyocardial
fibrosisbyquantifyinglategadoliniumenhancement.55
CardiopulmonaryExerciseTesting
Olderchildrenandadolescentswithaorticvalvestenosisareatriskforexerciseassociatedsymptomsandevensuddendeath.Asdescribedpreviously,with
progressivevalvarobstruction,leftventricularhypertrophyandanimbalance
betweencoronarysupplyandmyocardialdemandscanresultinmicrovascular
andsubendocardialischemia.48Duringexercisethepressurewithintheleft
ventriclerisesandincreasesoxygendemand,whiletheassociatedtachycardia
resultsinreduceddiastoliccoronaryfilling.Thisresultsinamyocardialoxygen
supplyanddemandmismatch.Thismaygiverisetomyocardialischemiaand
potentialformalignantdysrhythmiasandsuddendeath.56
Exercisestresstestinghaslongbeencorrelatedwithdiseaseseverityin
patientswithaorticstenosis,buttheprimaryroleistheevaluationandrisk
stratificationofasymptomaticpatientswithseveredisease.Symptom-limiting
stresstestinghasbeenshowntobesafeinpatientswithsevereaorticstenosis,
andnormalresultspredictadecreasedriskinadversecardiaceventswhen
comparedwithabnormalfindings.57Exercisetestingmaybeconsideredin
asymptomaticpatientstoensurethattheycantoleratedesiredphysicalactivities
withtheabsenceofsymptoms,exercise-inducedhypotension,orischemia.58
Symptomaticpatientswithsevereaorticstenosisshouldavoidtesting.
CardiacCatheterization
Duetoadvancesinnoninvasiveimaging,cardiaccatheterizationisused
primarilyforinterventionratherthanfordiagnosis.However,itcanbeused
selectivelyforinvasivehemodynamicmeasurementswhennoninvasivetestsare
inconclusiveorwhenthereisadiscrepancybetweennoninvasivetestsand
clinicalfindingsregardingtheseverityofaorticstenosis(Fig.44.19).
