Andersons pediatric cardiology 1170
Bạn đang xem bản rút gọn của tài liệu. Xem và tải ngay bản đầy đủ của tài liệu tại đây (151.43 KB, 3 trang )
Morphology
NormalAorticRoot
Tounderstandthemechanismsofobstructionatanylevelwithintheleft
ventricularoutflowtract,itisnecessaryfirsttounderstandthenormal
arrangement.Mostaccountsremainbasedontheconceptofanaortic“annulus,”
albeitthatthisenigmaticentityisrarelydescribedinconsistentandsatisfactory
fashion.4An“annulus,”ifdefinedliterally,isnomorethanalittlering.5There
areseveralringswithinthenormalaorticroot,butnoneofthemsupportsthe
leafletsoftheaorticvalve.6Theessenceofnormalityisthattheleafletsare
hingedwithinthearterialrootinsemilunarfashion(Fig.44.1).
FIG.44.1 Thenormalaorticroothasbeenopenedthroughanincisionin
theleftcoronaryaorticsinus,andtheleafletsoftheaorticvalvehavebeen
removed,showingthesemilunarattachmentsofthethreeleaflets.The
arrangementissuchtoincorporatecrescentsofventricularmyocardiumat
thebaseofthetwoleafletsattachedwithinthecoronaryarterialsinuses.
Trianglesoffibroustissueareincorporatedintotheoutflowtractbeneath
thezonesofappositionoftheleaflets,withthemembranousseptum
continuouswiththetrianglefoundbeneaththezoneofappositionbetween
therightcoronaryandnoncoronaryleafletsofthevalve.Notethat,inthis
normalheart,thereisseparationofthemembranousseptumfromtheright
fibroustrigoneduetorotationoftherootwithintheleftventricularoutflow
tract.
Therootitselfisformedbyinterlockingoftheaorticvalvarsinusesandthe
supportingventricularstructures.Becauseoftheinterlocking,thereisamarked
discrepancybetweenthelocusofthehemodynamic,asopposedtotheanatomic,
ventriculoarterialjunctions.Theanatomicventriculoarterialjunctionistheline
overwhichthefibroelasticwallsoftheaorticsinusesaresupportedbythebase
oftheleftventricle.Thelineisnotnearlyaswellseenintheleftventricular
outflowtractasintherightventricularinfundibulum.Thisreflectsthefactthat,
asshowninFig.44.1,itisonlytheleafletssupportedbythetwocoronary
arterialsinusesthathavemyocardiumformingpartoftheirbases.The
noncoronaryleafletoftheaorticrootandtheadjacentpartsoftheothertwo
leafletsaresupportedbyfibroustissueformedbythecontinuitybetweenthe
leafletsoftheaorticandmitralvalves.7Therightwardextentofthisareaof
fibrouscontinuityalsoincorporatesthemembranouspartoftheventricular
septum(seeFig.44.1).Nonetheless,asinthepulmonaryroot,thehemodynamic
ventriculoarterialjunctionismarkedbythesemilunarlinesofattachmentofthe
aorticvalvarleaflets(seeFig.44.1).Asaresult,inadditiontothemyocardium
incorporatedintothebasesofthecoronaryarterialvalvarsinuses,fibrous
trianglesareincorporatedatthedistalextentoftheventricularoutflowtract.The
trianglesextenddistallytothelevelofthemostdistalattachmentoftheleaflets
atthesinutubularjunction.Thisstructureisthemostobviousringintheleft
ventricularoutflowtract,markingthelineoverwhichtheexpandedaortic
sinusesbecomecontinuouswiththetubularaorta.Itmarksthedistalextentof
theaorticroot(Fig.44.2).
FIG.44.2 Imagespreparedbyvirtualdissectionofacomputed
tomographicdatasetobtainedfromanadultundergoinginvestigationfor
coronaryarterialdisease.Left,Howthefibroustriangleinterposingonthe
ventricularaspectofthesemilunarhingesoftherightcoronaryand
noncoronary,ornonadjacent,leafletsoftheaorticvalveextendstothe
sinutubularjunction(redcircle).Right,Viewlookingdownontheshortaxis
oftheroot.Thegreenlinesshowthelocationofthesinutubularjunction,
theanatomicventriculoarterialjunction,andvirtualbasalring.The
myocardiumsupportingpartofthebasesofthetwocoronaryaorticleaflets
hasbeencoloredorange.Notethattheanatomicventriculoarterialjunction
canbeidentifiedonlywithinthetwocoronaryaorticsinuses.Thesemilunar
hingesoftheleafletshavebeenoutlinedinred.(CourtesyDrShumpei
Mori,KobeUniversity,Japan.)
Becauseitisanintegralpartoftherootandvalvarcompetencedependsonits
integrity,itissomewhatillogicaltodescribestenosisatthislevelasbeing
“supravalvar.”Itisalsoillogicaltoconsideronlytheperipheralattachmentof
thevalvarleafletstothesinutubularjunctionasthe“commissures,”asis
currentlytheusualpractice.Definedliterally,acommissureisazoneof
apposition.Therefore,inadditiontotheperipheralendsofthezonesof
apposition,itisalsonecessarytorecognizethatthezoneextendsfromperiphery
ofthevalvarorificetoitscenter(Fig.44.3).Competenceofthevalvedepends
onsnugunionoftheleafletsalongthefullextentofthesezonesofapposition.
