Andersons pediatric cardiology 54
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atrioventriculartotheventriculoarterialjunctions(dottedlines).Thefine
apicaltrabeculationsareitsmostconstantfeature.
Ofthesethreecomponents,theapicaltrabecularcomponentismost
universallypresentinnormal,aswellasinmalformedandincomplete,
ventricles.Furthermore,itisthepatternoftheapicaltrabeculationsthat
differentiatesmorphologicallyrightfromleftventricles(seeFig.1.3).Thisisthe
caseevenwhentheapicalcomponentsexistasincompleteventricles,lacking
eitherinletoroutletcomponents,orsometimesbothofthesecomponents(Fig.
1.4).
FIG.1.4 Heartillustratingadoubleinletto,anddoubleoutletfrom,a
dominantleftventricle.Theaortaandpulmonarytrunkareseenarisingin
parallelfashionfromtheleftventricle,withtheaortaanteriorandtotheleft.
However,ontheanteriorandright-sidedshoulderofthedominantleft
ventricle,thereisstillasecondchambertobeseen,fedthrougha
ventricularseptaldefect.Thischamberistheapicaltrabecularcomponent
oftherightventricle(RV),identifiedbecauseofitscoarsetrabeculations.
Whenthemorphologyofindividualventriclesisidentifiedinthisfashion,all
heartswithtwoventriclescanbeanalyzedaccordingtothewaythattheinletand
outletcomponentsaresharedbetweentheapicaltrabecularcomponents.Tofully
describeanyventricle,accountmustalsobetakenofitssize.Itisnecessary
furthertodescribethewaythatthetwoventriclesthemselvesarerelatedwithin
theventricularmass.Thisfeatureisdescribedintermsofventriculartopology
becausetwobasicpatternsarefoundthatcannotbechangedwithoutphysically
takingaparttheventricularcomponentsandreassemblingthem.Thetwo
patternsaremirrorimagesofeachother.Theycanbeconceptualizedintermsof
thewaythat,figurativelyspeaking,thepalmarsurfaceofthehandscanbe
placedupontheseptalsurfaceofthemorphologicallyrightventricle.Inthe
morphologicallyrightventricleofthenormalheart,irrespectiveofitspositionin
space,onlythepalmarsurfaceoftherighthandcanbeplacedontheseptal
surfacesuchthatthethumboccupiestheinletandthefingersfitintotheoutlet
(Fig.1.5).
FIG.1.5 Diagramshowinghowthepalmarsurfaceoftherighthandcan
beplacedontheseptalsurfaceofthenormalmorphologicallyright
ventriclewiththethumbintheinletcomponentandthefingersextending
intotheventricularoutlet.(A)Theessenceofrighthandventricular
topology,alsoknownasad-ventricularloop.Thepalmarsurfaceoftheleft
handfitsincomparablefashionwithinthemorphologicallyleftventricle,but
therighthandistakenasthearbiterforthepurposesofcategorization.(B)
Themirror-imagednormalheart.Inthissetting,thepalmarsurfaceofthe
lefthandcanbeplacedontheseptalsurfaceofthemorphologicallyright
ventriclewiththethumbintheinletandthefingersintheoutlet.
Thereforetheusualpatterncanbedescribedasrighthandventricular
topology.18Theotherpattern,themirrorimageoftherighthandprototype,is
describedaslefthandventriculartopology.Inthislefthandpattern,seen
typicallyinthemirror-imagednormalheart,orinthevariantofcongenitally
correctedtranspositionfoundwithusualatrialarrangement,itisthepalmar
surfaceofthelefthandthatfitsontheseptalsurfaceofthemorphologicallyright
ventriclewiththethumbintheinletandthefingersintheoutlet.Thisisthe
essenceoflefthandtopology,orthe“l-ventricularloop”(seeFig.1.5).These
twotopologicpatternscanalwaysbedistinguishedirrespectiveofthelocation
occupiedinspacebytheventricularmassitself.Thereforealefthandpatternof
topologyisreadilydistinguishedfromaventricularmasswithrighthand
topologyinwhichtherightventriclehasbeenrotatedtooccupyaleft-sided
