Andersons pediatric cardiology 1189
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describedfortreatmentofsupravalvaraorticstenosis.165–167However,dueto
riskforinjurytotheaorticvalveandcoronaryarteries,surgicalinterventionis
preferred.
Thegoalofsurgicalinterventionistoachieveasymmetricenlargementofthe
aorticrootandothernarrowedsegmentsoftheaortaandheadvessels(Video
44.14and44.15).168Concomitantstenosisofcentralpulmonaryarteryand/or
coronaryarteriesshouldalsobeaddressedduringtheprocedureifindicated.
Aorticvalverepairmayalsoberequired.
Long-TermOutcomes
Severegeneralizedarterialformsandassociatedaorticvalvediseaseare
correlatedwithlatedeathandtheneedforreoperation.Thelong-termsurvival
rateisbetween70%and97%,andfreedomfromreoperationisapproximately
65%at20years.Reoperationsaremoreoftenduetoaorticvalveproblemsthan
progressivesupravalvaraorticstenosis.Reoperationalsoappearsmorecommon
innonsyndromicformscomparedwithpatientswithWilliams-Beuren
syndrome.160However,qualityoflifeisgenerallygood,withthemajorityof
patientsintheNewYorkHeartAssociationfunctionalclassI.169–172
SubvalvarAorticStenosis
Subvalvarstenosisisanobstructionoftheleftventricularoutflowtractbelow
theaorticvalve.Congenitalsubvalvaraorticstenosisisthesecondmostcommon
formofleftventricularoutflowtractobstructionandaccountsfor15%ofall
cases.173Thereisamalepredominancewithamale-to-femaleratiobetween
1.5:1and2.5:1.174
Thegeneticbasisforsubvalvaraorticstenosisisnotwelldefined,although
therehavebeenreportedfamilialcases.Thesefewreportedcasesoffamilial
subvalvarstenosiswereconsistentwithanautosomalrecessiveinheritance,but
otherpedigreesaresuggestiveofanautosomaldominantpattern.175–177
Comparedwithvalvarandsupravalvarstenosis,thegeneticfactorsinsubvalvar
aorticstenosisisfarlessdetermined.
Pathophysiology
Themostcommonformsorsubaorticstenosisareeitherafixedobstructiondue
toadiscretefibrousmembraneoradiffusetunnel-likeobstruction.This
conditionmayoccurinpatientswithassociatedcongenitalheartdiseases,
includingventricularseptaldefect,coarctationoftheaorta,interruptedaortic
arch,andatrioventricularseptaldefect.Thelesionmaydevelopinpatientswith
thesedefectsbeforesurgerybutmayalsoappearandprogresssignificantlyafter
surgicalcorrectionoftheassociateddefects.
Otherrarecausesofsubaorticstenosisincludeabnormalattachmentsofthe
mitralvalve,accessorytissue,abnormalinsertionofthemitralpapillarymuscle,
abnormalmuscularbandswithintheleftventricularoutflowtract,andspaceoccupyinglesionsintheleftventricularoutflowtract.Shonesyndromeis
characterizedbyacomplexofsubvalvaraorticstenosisinassociationwitha
supravalvarmitralring,parachutemitralvalve,andcoarctationoftheaorta.
Hypertrophicobstructivecardiomyopathyisassociatedwithdynamicsubvalvar
obstructionduetooppositionoftheanteriorleafletofmitralvalveagainstthe
hypertrophiedventricularseptum.
Asdiscussedpreviouslywithotherformsofleftventricularoutflowtract
obstruction,subvalvaraorticstenosiscanresultincompensatoryleftventricular
hypertrophy.Thisincreasedafterloadresultsinincreasedleftventricularsystolic
pressureandwallstress.Subvalvaraorticstenosisisgenerallyprogressive,but
thiscanbeveryvariablefromstablemildstenosistorapidworsening
obstruction.178Predictorsofdiseaseprogressionincludeincreasedgradientat
timeofdiagnosis,thepresenceofattachmentsofthesubaorticmembranetothe
mitralvalve,aorticvalvethickeningatdiagnosis,anddecreaseddistanceofthe
membranetotheaorticvalve.174Inaddition,subvalvaraorticstenosiscanresult
inturbulentflowinthesubaorticregionandinterferewiththemotionofthe
aorticvalveandresultinaorticregurgitation.Thisisanimportantphysiologic
consequenceandthedegreeofregurgitationgenerallyprogressesovertime.
ClinicalFeatures
Aswithvalvarandsupravalvarstenosis,symptomsareuncommonwith
subvalvarstenosis,evenwhenthenarrowingissevere.Thesepatientstypically
presentwithanewsystolicmurmur.Thisismostcommonlyaharshsystolic
ejectionmurmurthatisheardtheloudestattheleftmid-sternalborder.The
murmurwilloftenradiatetothecarotidsandthedegreeofobstructionwill
correlatewiththeintensityofthemurmur.Similartosupravalvarstenosis,an
ejectionclickwillnotbeheard.Theremaybeanearlydiastolicmurmurif
complicatedbysignificantaorticregurgitation.
Investigations
Electrocardiogram
Theelectrocardiogramisusuallynormal,buttheremaybevaryingdegreesof
leftventricularhypertrophywithstrainpattern.
ChestRadiograph
Thisisoftennormal,althoughenlargementofleftventricleandleftatriummay
bepresent.
Echocardiography
Aswithotherformsofleftventricularoutflowtractobstruction,transthoracic
echocardiographywithDoppleristhepreferredimagingmodalityforthe
diagnosisofsubvalvaraorticstenosis.Acomprehensiveevaluationis
fundamentaltothediagnosisandplanningforsurgicalintervention.The
