Andersons pediatric cardiology 1806

patientswithcongenitallymalformedheartscanbeplacedintooneoftwo
groups.4,5Thefirstgroupismadeupofthosewithbiventricularatrioventricular
connections,specificallyconcordant,discordant,andmixedatrioventricular
connections(seeChapter2).Inthesecondgroup,theatrioventricularjunctions
aresupportedbyonlyoneventricle,eitherbecauseofdouble-inletventricleor
becauseoneofthejunctionsiscompletelyabsent.Thereisaverysmallthird
groupinwhichthereisabsenceofoneoftheatrioventricularconnectionsbut
withstraddlingandoverridingofthesolitaryatrioventricularvalve.This
combinationproducesauniatrialbutbiventricularconnection(Fig.69.5).6Inall
thepatientshavinguniventricularatrioventricularconnections,apartfromthe
verysmallminorityhavingsolitaryandindeterminateventricles,asecond
ventricleistobefoundwithintheventricularmass(Fig.69.6).Inthepresenceof
thissecondchamber,itfollowsthattheheartsthemselvesarenot
“univentricular.”Whenfound,thesecondventricleisincomplete,lackingatthe
leastitsinletandoftenalsolackinganydirectoutletotherthantheventricular
septaldefect.Onrareoccasions,itmaybepossiblesurgicallytoseptatethe
dominantventricleinthesettingofdoubleinletandhencetorestore
biventricularcirculations.Patientswithuniventricularatrioventricular
connectionscurrentlyarealmostalwaystreatedbyconversiontotheFontan
circulation,asaremanypatientswithbiventricularatrioventricularconnections.
Insuchcircumstances,alltheheartswillbecomefunctionallyuniventricular
subsequenttocreationoftheFontanarrangement.Theadditionoftheword
“functionally,”therefore,providesthelogicforthegroupingofthevarious
entitiestobedescribedinthischapter.7


FIG.69.1 Anatomicallysolitaryventricle.Thehearthasbeenopenedin
clam-likefashion,showingadoubleinlettoandadoubleoutletfroma
ventriclewithexceedinglycoarseapicaltrabeculations.Theonlyseptum
presentisthemuscularoutletseptum.

FIG.69.2 Heartwithdouble-inletleftventricle(LV)sectionedtoreplicate
theparasternalechocardiographicprojection.ThereisadominantLVwith
anincompleterightventriclepositionedanterosuperiorly.Thechannel
betweenthechambersisaventricularseptaldefect,beingpositioned


betweentheapicalandoutletseptalcomponents.LAVVandRAVV,Left
andrightatrioventricularvalves.

FIG.69.3 Comparisonofthesmallchamberinclassictricuspidatresia
(right)withthesecondventricularchamberseeninthe“Holmesheart,”
whichhasadouble-inletleftventricle,butwithconcordantventriculoarterial
connections(left).Intermsoftheircomponentmakeup,withboth
chamberslackingananatomicinletotherthantheventricularseptaldefect
(VSD),thechambersareidentical.Conventionalwisdom,however,had
dictatedthattricuspidatresiashouldbeinterpretedintermsofa
“biventricularheart,”whereasadouble-inletleftventriclerepresenteda
“singleventricle.”RV,Rightventricle.