Andersons pediatric cardiology 59
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junctions.Thisarrangementproducesconcordantatrioventricularconnections.
Suchconcordantconnectionscanbefoundwitheitherusuallyarrangedatrial
appendagesorinthemirror-imagedarrangement(Fig.1.15).
FIG.1.15 Concordantatrioventricularconnectionscanexistinusualand
mirror-imagedpatterns.Almostwithoutexception,atriumswithusually
arrangedappendagesarejoinedtoaventricularmasswithrighthand
topology,whereasatriumswithmirror-imagedappendagesarejoinedtoa
ventricularmasswithlefthandtopology.Exceptwhentheseassociations
arenotpresent,itisnotnecessaryalsotostatethetopologyofthe
ventricles.
Thesecondarrangement,whichisthereverseofthefirst,isagainindependent
ofrelationshipsorvalvarmorphology.Itproducesdiscordantatrioventricular
connectionsandcanagainbefoundintheusualormirror-imagedsituations.
Whentheatrialappendagesaremirrorimagedinpatientswithdiscordant
atrioventricularconnections,theventriclesaretypicallyintheirexpectedpattern
and,inotherwords,showrighthandtopology(Fig.1.16).
FIG.1.16 Arrangementsthat,almostwithoutexception,produce
discordantatrioventricularconnections.
Thesefirsttwoarrangements(seeFigs.1.15and1.16)arefoundwhenthe
atrialappendagesarelateralized.Theotherbiventricularatrioventricular
arrangement,inwhicheachatriumisjoinedtoaseparateventricle,isfoundin
heartswithisomericappendages,whetherofrightorleftmorphology.Because
oftheisomericnatureoftheappendages,thisthirdarrangementcannot
accuratelybedescribedintermsofconcordantordiscordantconnections.Itisa
discretebiventricularpatterninitsownright,whichismixed(Fig.1.17).It,too,
isindependentofventricularrelationshipsandatrioventricularvalvar
morphologiesandrequiresspecificationofventriculartopologytomakethe
descriptioncomplete.
FIG.1.17 Inthesettingofisomericatrialappendages,withright
isomerismasshownintheillustration,biventricularconnectionsof
necessityaremixedirrespectiveofventriculartopology.Thereforetofully
describethesepatterns,itisnecessarytospecifyboththemorphologyof
theatrialappendagesandtheventriculartopology.
Therearealsothreepossiblejunctionalarrangementsthatproduce
univentricularatrioventricularconnections(Fig.1.18).Thefirstiswhenthe
cavitiesofright-andleft-sidedatrialchambersareconnecteddirectlytothe
sameventricle.Thisiscalleddouble-inletatrioventricularconnection,
irrespectiveofwhethertheright-andleft-sidedatrioventricularjunctionsare
guardedbytwoatrioventricularvalvesoracommonvalve.Theothertwo
arrangementsexistwhenoneatrioventricularconnectionisabsent,givingabsent
right-sidedandabsentleft-sidedatrioventricularconnection,respectively.The
patternsacrossthejunctionsthatproduceuniventricularatrioventricular
connectionsaredifferentfromthosefoundwithbiventricularconnections.Not
onlyaretheyindependentofventricularrelationshipsandvalvarmorphology,
buttheyarealsoindependentofatrialandventricularmorphologies.Heartswith
concordantordiscordantatrioventricularconnectionscanexistonlywhen
usuallyarrangedormirror-imagedatrialchambersareeachjoinedtoseparate
ventricles.Aheartwithbiventricularmixedconnectioncanonlybefoundwhen
eachoftwoatrialchambershavingisomericappendagesisjoinedtoaseparate
ventricle.Incontrast,double-inlet,absentright-sided,orabsentleft-sided
atrioventricularconnectionscanbefoundwithusuallyarranged,mirror-imaged,
orisomericatrialappendages.Eachtypeofuniventricularatrioventricular
connectioncanalsobefoundwiththeatriumsconnectedtoadominantright
ventricle,dominantleftventricle,ormorphologicallyindeterminateventricle
(seeFig.1.18).
