Andersons pediatric cardiology 1187
Bạn đang xem bản rút gọn của tài liệu. Xem và tải ngay bản đầy đủ của tài liệu tại đây (85.95 KB, 3 trang )
afterabriefperiodofpreoperativestabilizationwithmedicalafterloadreduction
therapy.Ingeneral,theoperationshouldbetimedasearlyaspossibleafter
diagnosisofthedefect,evenwhenthecommunicationissmall,tominimize
secondarydeteriorationoftheaorticvalve.
Duringsurgicalintervention,anaortotomyisperformedandtheendsof
tunnelareidentifiedaboveandbelowthevalve.Theaorticvalveisalso
carefullyexamined.Positionsofcoronaryarteriesostiaarenoted.Boththeaortic
andventricularendsofthetunnelshouldbeclosedwithseparatepatchesof
Dacronorpericardium.Theventricularendisapproachedthroughtheaortic
valveortunnelitselfifinjurytotheconductionsystemisaconcern.Approach
throughtherightatrium,pulmonaryvalve,ortunnelitselfisusedwhenthe
tunnelenterstherightventricle.Asmallslitliketypeoftunnelcanbeclosed
primarily,ifdistortionoftheaorticvalvecanbeavoided.
Long-TermOutcomes
Long-termoutcomedataarelackingduetotherarityofthislesion.Thesurgical
mortalityraterangesbetween11%and20%inmostseries.147,148Patchclosure
ofbothendsofthetunnelisrecommendedtopreventaorticannulusandvalve
distortion,aswellaspotentialforreopeningofthetunnelcommunication.Ifthe
ventricularendisleftopen,ablindchambercandevelopfromsystolicinflow
andpulsatilitywithaneurysmformationoftheventricularseptum,whichcan
distorttheaorticvalveandcauseprogressiveaorticinsufficiency.Progressive
aorticregurgitationremainsapotentiallong-termproblemandseemstobemore
prevalentwhentheinitialoperationisperformedatanolderage.149,150
SupravalvarAorticStenosis
Introduction
Congenitalsupravalvaraorticstenosisistheleastcommonformofleft
ventricularoutflowtractobstruction,withanestimatedincidenceof1in20,000
livebirths.151Mostcommonly,supravalvaraorticstenosispresentsasadiscrete,
hourglass-likenarrowingoftheascendingaortanearthesinotubularjunction.
However,inapproximately25%to30%ofcases,thereismorediffuse
narrowingoftheascendingaortathatmayextendintotheaorticarch.152,153Itis
nowrecognizedthatcongenitalsupravalvaraorticstenosisrepresentsone
manifestationofadiffusearteriopathycharacterizedbythickeningofthemedia
orintimalayers.Thisarteriopathyresultsinprogressivenarrowingofthe
ascendingaorta,aswellasothersystemicandpulmonaryarteries.
Genetics
Congenitalsupravalvaraorticstenosisresultsfromhaploinsufficiencyofthe
elastin(ELN)geneonchromosome7q11.23.154TheELNgeneencodesforan
elastin-precursortropoelastin,whichisexpressedinsmoothmusclecellsduring
theearlystagesofdevelopment.Elastin,incombinationwithotherextracellular
proteins,formselastinfiberswithinthearterialmediaandfunctionstoprovide
distensibility,orelasticity,tothevasculature.DisruptionoftheELNgeneresults
inreducedanddisorganizedelastinfibersinthearterialmedia,alongwith
increasednumberofhypertrophiedsmoothmusclecellsandincreasedcollagen
deposition.155
Theconditionisinheritedasanautosomaldominantdiseasewithincomplete
penetranceandvariableexpressivity.151MicrodeletionoftheELNgeneresultsin
Williams-Beurensyndrome,whichmanifestsasanelastinarteriopathyin
additiontoseveralotherfeatures,includingintellectualdisability,
hypercalcemia,andfacialabnormalities.156Theestimatedprevalenceof
supravalvaraorticstenosisinpatientswithWilliams-Beurensyndromeis
approximately70%.157PointmutationsintheELNgeneresultinnonsyndromic
orfamilialformsofsupravalvaraorticstenosis.Patientswithnonsyndromic
supravalvaraorticstenosishaveasimilararteriopathyaspatientswithWilliamsBeurensyndromebuttypicallyhavenormalintelligenceandlackdysmorphic
features.158
Pathophysiology
Supravalvaraorticstenosisischaracterizedbynarrowingoftheascendingaorta
duetoprogressivethickeningofthemediaorintimalayersoftheaorticwall.
Histologydemonstratesreducedanddisorganizedelastinfibersinthearterial
media,alongwithincreasednumberofhypertrophiedsmoothmusclecellsand
increasedcollagendeposition.155Otherarterieswithhighelastinfibercontent
canalsobeaffected,includingprogressivestenosisoftheproximaldescending
aorta,aswellaspulmonary,coronary,mesenteric,andrenalarteries.159Aortic
andmitralvalveabnormalitieshavealsobeenreported.160
Stenosisoftheascendingaortaresultsinincreasedafterloadtotheleft
ventricle,resultingincompensatoryleftventricularhypertrophy,similartothe
remodelingchangesseenwithvalvaraorticstenosis.However,unlikeaortic
stenosis,thecoronaryarteriesarealsosubjecttohighpressure.Coronary
insufficiencyisaconcerningcomplicationinthissettingandmayresultfroma
combinationofthickeningofthecoronaryostia,thickeningoftheaorticwall
abovethecoronaryostia,prematureatherosclerosis,oradhesionoftheaortic
valveleaflettothesinotubularjunction.161
Suddendeathhasbeenwell-reportedinpatientswithsupravalvaraortic
stenosisandisbelievedtobeprecipitatedbyacutecoronaryischemia.Therisk
ofsuddendeathinpatientswithWilliams-Beurensyndromeisestimatedtobe1
in1000patientyearsandis25to100timeshighercomparedwithanagematchedcontrolpopulation.162Hypertensionisalsocommon,eveninthe
absenceofrenalarterystenosis.163
ClinicalFeatures
Mostpatientswithsupravalvaraorticstenosisareasymptomaticanddiagnosed
afterauscultationofaheartmurmur.PatientswithWilliams-Beurensyndrome
maybediagnosedduetotheirnoncardiacmanifestations,includingdysmorphic
facies,intellectualdisability,orhypercalcemia.Theheartmurmuris
characterizedasasystolicejectionmurmurloudestattherightuppersternal
borderwithradiationtotheneck.Unlikevalvaraorticstenosis,thereisno
systolicclick.Somepatientsmayhavedisproportionatelyhighbloodpressurein
therightarm.ThisphenomenonisduetotheCoandaeffectofthehigh-velocity
