Andersons pediatric cardiology 53
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intrinsicmorphologyandthatonepartoftheheart,whichisitselfvariable,
shouldnotbedefinedonthebasisofanothervariablestructure.Whenthis
eminentlysensibleconceptisappliedtotheatrialchambers,theconnectionsof
thegreatveinsareobviouslydisqualifiedasmarkersofmorphologicrightnessor
leftnessbecause,asdiscussedpreviously,theveinsdonotalwaysconnectto
theiranticipatedatriums.Fortunately,thereisanothercomponentoftheatrial
chambersthat,inourexperience,hasbeenalmostuniversallypresentandthat,
onthebasisofthemorphologyofitsjunctionwiththeremainderofthe
chambers,hasenabledusalwaystodistinguishbetweenmorphologicallyright
andleftatriums.Thisistheappendage.Themorphologicallyrightappendage
hastheshapeofablunttriangleandjoinsoverabroadjunctionwiththe
remainderoftheatrium.Thejunctionismarkedexternallybytheterminal
grooveandinternallybytheterminalcrest.Itsmostsignificantfeatureisthatthe
pectinatemusclesliningtheappendageextendaroundtheparietal
atrioventricularjunctiontoreachthecardiaccrux(Fig.1.2A).
FIG.1.2 (A)Short-axisviewoftherightatrioventricularjunctionfrom
above,theatriumhavingbeenopenedwithacutparalleltothe
atrioventricularjunction,andwithsubsequentreflectionofthewallofthe
appendage.Notethatthepectinatemuscleswithintheappendageextend
allaroundthevestibuleofthetricuspidvalve.(B)Short-axisviewoftheleft
atrioventricularjunctionphotographedfromabovefromthesameheart.
Thepectinatemusclesareconfinedwithinthetubularappendage,sothat
theinferiorwalloftheatriumissmooth.Thiscontainsthecoronarysinus
withinthemorphologicallyleftatrioventricularjunction.Notealsothetypical
appearanceofthemorphologicallyleftsideoftheseptum.
Themorphologicallyleftappendage,incontrast,ismuchnarrowerand
tubular.Ithasanarrowjunctionwiththeremainderoftheatrium,thejunction
beingmarkedneitherbyaterminalgroovenorbyamuscularcrest.The
pectinatemusclesareconfinedwithinthemorphologicallyleftappendage,with
thewallsoftheremainderoftheatriumbeingsmoothastheyextendtothe
cardiaccrux(seeFig.1.2B).
Themorphologicmethodalsoshowsitsvaluewhenappliedtotheventricular
mass,whichextendsfromtheatrioventriculartotheventriculoarterialjunctions.
Withintheventricularmassasthusdefined,therearealmostalwaystwo
ventricles.Descriptionofventricles,nomatterhowmalformedtheymaybe,is
facilitatediftheyareanalyzedaspossessingthreecomponents.Thefirstisthe
inlet,extendingfromtheatrioventricularjunctiontothedistalattachmentofthe
atrioventricularvalvartensionapparatus.Thesecondpartistheapicaltrabecular
component.Thethirdistheoutletcomponent,supportingtheleafletsofthe
arterialvalve(Fig.1.3).
FIG.1.3 (A)Threecomponentpartsofthemorphologicallyrightventricle,
whichextendsfromtheatrioventriculartotheventriculoarterialjunctions
(dottedlines).Thecoarseapicaltrabeculationsarethemostconstantof
thesefeatures.(B)Threecomponentpartsofthemorphologicallyleft
ventricleofthesameheart.Theventricularcavityagainextendsfromthe
