Andersons pediatric cardiology 1813

Double-InletVentricle
Thecombinationsdescribedearlierforatrioventricularvalvaratresiaarealsoto
befoundinpatientshavingadouble-inletventricle,thedifferencebeingthatall
suchpatientswillhaveuniventricularatrioventricularconnections.Adouble
inletisfoundwhenbothatrioventricularjunctions,intheirgreaterpart,are
supportedbythesameventricle.Inthemajorityofcases,theventriclewillbe
morphologicallyleft.Theincompleterightventricleformsthesecondchamber
withintheventricularmass(Fig.69.17).Asalreadydiscussed,formanyyearsit
wasthoughtthatthesecondchamberwasnomorethananinfundibularoutlet
chamber.Theseptumseparatingthesmallchamberfromthedominantventricle,
however,carriestheatrioventricularconductionaxisandisnourishedby
delimitingcoronaryarteries.Itseparatestheapicalcomponentofthedominant
ventriclefromanapicalpartofthesecondchamber.Thisistheapicalventricular
septum,meaningthattheholebetweenitscrestandthemuscularoutletseptum
isaventricularseptaldefect(seeFig.69.17).Theincompleterightventricleis
alwayscarriedontheanterosuperiorshoulderofthedominantleftventricle.Itis
mostusuallyleft-sidedbutcanberight-sidedordirectlyanterior.Inmost
instances,itsupportstheaorta,withthepulmonarytrunkarisingfromthe
dominantleftventricle;inotherwords,therearediscordantventriculoarterial
connections,ortransposition.Inthissetting,theoutletcomponentofthe
ventricleisshort.Inaminorityofcases,theventriculoarterialconnectionscan
beconcordant.Whenthisisassociatedwithspiralingofthepulmonarytrunk
relativetotheaorta,thearrangementisknownastheHolmesheart.The
incompleterightventricleisvirtuallyindistinguishablefromthecomparable
chamberasseeninclassicaltricuspidatresia(seeFig.69.2).Inevenrarer
circumstances,thearterialtrunkscanbeparallelwhentheventriculoarterial
connectionsareconcordant.Thisisthearrangementknownasananatomically
correctedmalposition;ithasalsobeendescribedasisolatedventricular
discordance.Asstatedearlier,inconsideringthearrangementfoundwith
atrioventricularvalvaratresia,itisbettersimplytodescribethesituationas
concordantventriculoarterialconnectionswithparallelarterialtrunks.Inother

situations,botharterialtrunkscanariseeitherfromthedominantorthe
incompleteventricle.Pulmonaryatresiacanalsobefound.Aswithtricuspid
atresia,narrowingoftheventricularseptaldefectisassociatedwithcoarctation
orinterruptionoftheaorticarchwhentheventriculoarterialconnectionsare


discordant.Suchnarrowingoftheventricularseptaldefectwouldobviously
producesubpulmonaryobstructionshouldtheventriculoarterialconnectionsbe
concordant.

FIG.69.17 Characteristicfeaturesofdouble-inletleftventricle.Left,
Replicatingthefour-chambersection,bothatrioventricular(AV)junctions
arecommittedtothedominantleftventricle.Right,Incompleteright
ventricle,whichlacksitsinletcomponent.

Adoubleinletcanalsobefoundwhenbothatrioventricularconnectionsare
supportedbythedominantrightventricle.Theleftventricleisincomplete.The
incompleteleftventricleisalwaysfoundposteroinferiorly,or“inthehip
pocket,”relativetothedominantventricle.Mostusuallyitislocatedinaleftsidedposition,butitcanrarelyberight-sided.Theatrioventricularjunctionsin
thesettingofdouble-inletrightventricleareusuallyguardedbyacommon
atrioventricularvalve,asindeedcanalsobethecasewithdouble-inletleft
ventricle.Theconnectionofthejunctionstothesameventricleistheessenceof
adoubleinlet,andnotthenatureofthevalvesguardingthem.Lessfrequently,a
double-inletrightventriclecanbefoundwithseparaterightandleft
atrioventricularvalves(Fig.69.18).Inthesettingofdouble-inletrightventricle,


botharterialtrunksalsousuallyarisefromthedominantventricle,althoughitis
possibletofindconcordantventriculoarterialconnections.Thecombinationwith
acommonatrioventricularvalveisparticularlyfrequentinthesettingofright

isomerism.Adouble-inletventriclecanrarelybefoundwhenthereisasolitary
chamberwithintheventricularmass(seeFig.69.1).Insuchsettings,the
ventriclehasparticularlycoarseapicaltrabeculations.Itmaybedifficult,inthe
clinicalsetting,tomakethedistinctionfromdouble-inletrightventricle.Inthe
lattersetting,theincompleteleftventricleisoftennomorethanaslitinthe
posteroinferiorventricularwall.Thesolitaryventriclecanalsobeconfusedwith
ahugeventricularseptaldefect.Anapicalridge,however,willseparatethe
apicalcomponents,withtherightventricularapexhavingcoarsetrabeculations
andtheleftventricularapexhavingfinetrabeculations.Suchpatientswithhuge
ventricularseptaldefectsshouldbeamenabletobiventricularsurgicalrepair.
Crossingofthetensionapparatusoftheatrioventricularvalvescoupledwiththe
coarseapicaltrabeculationsisusuallysufficienttoruleouttheoptionsfor
biventricularrepairwhentheventricleisofsolitaryandindeterminate
morphology(seeFig.69.1).Theconductionaxisisalsofrequentlybizarreinthe
settingofthesolitaryventricle,particularlywhenassociatedwithright
isomerism.

FIG.69.18 Twoheartswithdouble-inletrightventricle(RV)sectionedin
thefour-chamberplane.Ascanbeseen,bothatriaconnecttothe
dominantRVirrespectiveofwhethertheatrioventricularjunctionsare
guardedbytwoseparateatrioventricularvalves(A)oracommon