Andersons pediatric cardiology 1183
Bạn đang xem bản rút gọn của tài liệu. Xem và tải ngay bản đầy đủ của tài liệu tại đây (82.54 KB, 3 trang )
AorticRegurgitation
Aorticregurgitationisararefindingatbirthbutcandevelopovertimeduetoa
varietyofcongenitaloracquiredconditions(Box44.3).Congenitalbicuspid
aorticvalveisacommoncauseofaorticregurgitation,whichcandevelopdueto
redundantorprolapsingcusps,endocarditis,orafteraninterventiontorelieve
aorticstenosis.Inthepresenceofaventricularseptaldefect,theaorticvalve
cuspsmayprolapsethroughthedefectresultinginmalcoaptationofthevalve
cuspsandaorticregurgitation.Turbulencefromsubvalvaraorticstenosiscan
distorttheaorticvalvecuspsandhasawell-knownassociationwithprogressive
aorticregurgitation.Aortopathiesinthesettingofconnectivetissuedisordersor
congenitalheartdiseasecanresultindilationoftheaorticsinusesofValsalva
and/orsinotubularjunction,aswellastheaorticannulus,preventingadequate
leafletcoaptationandresultinginregurgitation.Finally,aorticregurgitationcan
occurinthesettingofrheumaticheartdiseaseduetoacombinationofleaflet
thickening,coaptationdefect,restrictedleafletmotion,and/orleafletprolapse.
Box44.3
EtiologiesforAorticValveRegurgitationin
PediatricPatients
Congenitalbicuspidaorticvalve
Prolapseofaorticvalvecuspsthroughventricularseptaldefect
Distortionoftheaorticvalvefromsubaorticstenosis
Dilationoftheaorticannulusassociatedwithaorticrootaneurysm
Infectiveendocarditis
Rheumaticheartdisease
Pathophysiology
Chronicaorticregurgitationresultsinincreaseinpreloadandend-diastolic
volumeoftheleftventricle.Thisvolumeload,inturn,increasesthewallstress
andafterloadontheventricle.InaccordancewiththelawofLaplace,theleft
ventricleadaptsandnormalizeswallstressbyincreasingwallthicknessinthe
formofeccentrichypertrophy.Eccentrichypertrophyresultsinanincreasein
cardiacmasswithincreasedchambervolume,maintaininganormalratioofleft
ventricularwallthicknesstochamberradius.113
Onacellularlevel,thisoccursthroughelongationofmyocardialfibersand
additionofnewsarcomeresinseries.43Duringthiscompensatedphase,left
ventricularsystolicfunctionispreservedandpatientsremainrelatively
asymptomatic.Withincreasingseverityandchronicityofaorticregurgitation,
thecompensatorymechanismsoftheleftventriclecannotbemaintained.
Eventually,ifuntreated,theleftventricularfillingpressuresincreaseand
ejectionfractiondecreases,resultinginsymptomsofexertionaldyspneaand
heartfailure.
ClinicalFeatures
Aorticregurgitationistypicallywelltolerated,andsymptomsarevery
uncommonduringinfancyandchildhood.Symptomsusuallymanifestwhen
chronicsevereregurgitationisuntreatedandeventuallyleadstoleftventricular
systolicdysfunction.Thesesymptomsincludepalpitationsanddyspneawith
exertion,angina,andcongestiveheartfailure.
PhysicalExamination
Theclassicexamfeaturesofchronicsevereaorticregurgitationarereflectiveof
awidepulsepressure.Thepulseshaveanabruptupstrokewithrapidcollapse,
alsoknownasthewaterhammerpulseofWatsonorCorriganpulse.Theheadof
thepatientmaynodwitheachcardiaccycle,afeaturecalledthesignofde
Musset.Astheleftventricledilatesovertime,thereisevidenceofa
hyperdynamicandlaterallydisplacedapicalimpulseonprecordialexamination.
Auscultationrevealsthecharacteristicblowingearlydiastolicmurmur,which
isheardalongtheupperleftsternalborderwithradiationtotheapex.
Interventionsthatincreaseafterload,suchassquattingandValsalvamaneuver,
canaccentuatethemurmurofaorticinsufficiency.Asystolicejectionmurmur
canalsobeheardandisrelatedtotheincreasedstrokevolumeacrosstheleft
ventricularoutflowtractand/ortheconcomitantpresenceofaorticvalve
stenosis.Amid-diastolicmurmurattheapex,theAustinFlintmurmur,maybe
heard.Thismurmurresemblesmitralstenosisandissecondarytotheanterior
leafletofthemitralvalvebeingheldinapartiallyclosedpositionduetothe
aorticregurgitantjet.Incaseswithleftventriculardysfunction,itmayalsobe
possibletohearathirdheartsound.
Investigations
Electrocardiogram
Theelectrocardiographicchangesdependonseverityanddurationof
regurgitation.Patternofleftventricularhypertrophydevelopswithincreased
voltagesintheleftprecordialleadsanddeepSwaveinleadV1.TheTwaves
usuallyremaintallanduprightuntilleftventriculardysfunctionhasoccurred,
whendepressionandinversionoftheSTsegmentispresent.AprominentQ
waveinthelateralchestleadsiscommonlyseenasaresultofvolumeloadingof
theleftventricle.
ChestRadiograph
Thechestradiographisoftennormalwithmildandmoderateaortic
regurgitation.Withsevereregurgitation,thechestradiographyshows
cardiomegaly,withleftventricleandatrialdilation.Theremayalsobe
prominenceoftheascendingaortaandaorticknuckle.
Echocardiogram
Transthoracicechocardiogramistheprimaryimagingmodalitytoassessthe
presenceandseverityofaorticregurgitation,inconjunctionwithanevaluation
ofleftventricularfunction.Themorphologyoftheaorticvalvecanbeassessed
intheparasternalshortaxisview.Thepresenceofassociatedleft-sided
pathologycanbedetermined,aswellasanassociatedventricularseptaldefector
subaorticstenosis,whenthesearethemechanismsforregurgitation.
TheseverityoftheaorticregurgitationisbestassessedbyDoppler
echocardiography.ColorflowDopplerisusefulforprovidingasemiquantitative
measurementofdegreeofregurgitation.Thesizeofthejet(Fig.44.20;Videos
44.8and44.9)justdistaltotheleafletshasareasonablecorrelationwith
regurgitantvolume.54Thepressurehalf-timeoftheaorticregurgitationDoppler
jetcorrelateswiththedegreeofregurgitationbutislessusefulinpediatric
patientsduetoafasterheartrate.
