Andersons pediatric cardiology 74
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FIG.2.16 Parietalwalloftherightventriclereflectedtoshowitsseptal
surface.Theprominentseptomarginaltrabeculation,orseptalband,
bifurcatesattheventricularbasetoclaspthesupraventricularcrest,which
interposesbetweenthehingesoftheleafletsofthetricuspidand
pulmonaryvalves.
Themedialpapillarymusclearisesfromitsposterocaudallimb,whilethe
anteriorpapillarymusclespringsfromitsbodytowardtheventricularapex.The
moderatorbandcontinuesonfromtheanteriorpapillarymuscletoreachthe
parietalventricularwall.Afurtherseriesoftrabeculationsextendfromthe
anteriorsurfaceoftheseptomarginaltrabeculation.Theyrunintotheparietal
marginofthetrabecularzoneastheseptoparietaltrabeculations.
Theoutletcomponentoftherightventricleisrelativelysmoothwalled.It
formsthefree-standingsleeveofmusculaturethatsupportstheleafletsofthe
pulmonaryvalve.Theleafletsofthevalvethemselvesareattachedinsemilunar
fashionwithinthesleeve,crossingthecircularjunctionbetweenventricular
muscleandthefibroelasticwallofthepulmonarytrunk(Fig.2.17).
FIG.2.17 Subpulmonaryoutflowtractopenedandspreadtoshowthe
ventriculoarterialjunction,withtheleafletsofthepulmonaryvalveremoved.
Thesemilunarhingesofeachleafletcrossthejunctionsuchthatcrescents
ofmyocardiumareincorporatedintothebaseofeachsinus,withtriangles
ofarterialwallincorporatedaspartoftheventricularoutflowtract.
Becauseofthisarrangement,threecrescentsofventricularmusculatureare
incorporatedwithinthebasesofthesinusesofthepulmonarytrunk,whilethree
triangularareasofpulmonarytrunkareincorporatedwithintheventricular
outflowtractbeneaththetipsofthezonesofappositionbetweenthevalvar
leaflets.9Thevalvarleafletsdonotpossessanannulusinthesenseofafibrous
ringsupportingtheirattachmentsincircularfashion.Instead,theleafletsare
hingedinsemilunarfashion,producingacrown-likearrangementwhenviewed
inunopenedfashion(seeFig.2.2,right).Themostobviouscircleswithinthe
outflowtractareeithertheanatomicventriculoarterialjunction(seeFig.2.17),
orelsethesinutubularjunctionbetweenthevalvarsinusesandthepulmonary
trunk.Avirtualringcanalsobeconstructedbyjoiningtogetherthemost
proximalpartsofthethreesemilunarleaflets.Thisistheechocardiographic
annulus,whichhasnodirectanatomiccounterpart(Fig.2.18).
FIG.2.18 Ringsthatexistwiththearterialroots.Thevirtualring
constructedbyjoiningtogethertheproximalattachmentsofthesemilunar
leafletsisconsideredtorepresenttheechocardiographicannulus.As
showninFig.2.17,ithasnoanatomiccounterpart.
Thefree-standingsubpulmonaryinfundibularsleeveisacomponentofthe
supraventricularcrest.Oftenillustratedasaseptalstructure,inrealityitisthe
innercurvatureoftherightventricularwall,andiswelldescribedasthe
ventriculoinfundibularfold.Itisthepresenceoftheinfundibularsleevethat
makesitpossiblesurgicallytoremovethepulmonaryrootasanautograftinthe
Rossprocedure.10
MorphologicallyLeftVentricle
Aswiththerightventricle,theleftventriclepossessesinlet,apicaltrabecular,
andoutletcomponents(Fig.2.19).
