Andersons pediatric cardiology 1811

FIG.69.13 Effectsofthefistulouscommunicationsbetweenthecavityof
therightventricleandthecoronaryarteries,whichareafeatureofpatients
withthefunctionallyuniventricularvariantofpulmonaryatresiaandintact
ventricularseptum.Left,Muralhypertrophyhassqueezedouttheapical
andoutletventricularcomponents.Afistulouscommunicationhas
producedectasiaoftheanteriorinterventricularcoronaryartery(right).


AtrioventricularValvarAtresia
Thevariationsinmorphologyencounteredinthesettingofpulmonaryatresia
withanintactventricularseptumservedtodemonstratehowheartswith
comparablesegmentalconnectionscanbefunctionallyuniventricularor
functionallybiventriculardependingonthesizeoftheventricularcavityandthe
morphologyoftheventricularoutflowtract.Heartshavingatrioventricular
valvaratresia,incontrast,willalwaysbefunctionallyuniventricular.The
functionallyuniventriculararrangementcanbefoundinthesettingofeither
univentricularorbiventricularatrioventricularconnections.Thisanatomic
heterogeneityisfurthercomplicatedbythepossibilitiesregardingventricular
topologyandventriculoarterialconnections.Thespaceavailablehereprecludes
thepossibilityofillustratingallthepotentialcombinations.Itwaspatientswith
atrioventricularvalvaratresia,specificallytricuspidatresia,thatwerethefirst
individualstobeconvertedtotheFontancirculation.Atthatearlystage,itwas
believedthatpulsatileflowwouldbeanadvantageinthepulmonarycircuit,so
valveswereplacedatthevenoatrialjunctions.Attemptsweremadetoinclude
therightventricleinthecirculation.Itisnowacceptedthatthebestsurgical
resultsareobtainedbyexcludingtherightventricle,orasecondhypoplastic
ventricle,fromthepulmonarycircuit.Atthetimeoftheinitialexperiences,it
wasgenerallybelievedthatatrioventricularvalvaratresiawasproducedbyan
imperforateatrioventricularvalve.Suchananatomicvariantcanbefound(Fig.
69.14,left)butisrare.Whenpresent,itisusuallyinthesettingofpulmonary
atresiawithintactventricularseptumoranimperforateEbsteinmalformation.

Thesubstrateforthecommonestvariantoftricuspidatresia,however,isabsence
oftherightatrioventricularconnection(Fig.69.14,right).Mitralatresiacanalso
beproducedbyanimperforateatrioventricularvalve(Fig.69.15A)orby
absenceoftheleftatrioventricularconnection(Fig.69.15B).Problemsare
sometimesencounteredindescribingthearrangementas“mitral”or“tricuspid”
atresia.IntheheartsshowninFig.69.15,therightatriumisconnectedtothe
morphologicallyrightventricle;thisventricleisdominantintheheartshown,
withabsenceoftheleftatrioventricularconnection.Theleftatrioventricular
connectioncanalsobeabsentwhentherightatriumisconnectedtoadominant
leftventricle.Inthelattersituation,theincompleterightventricleisusually
carriedontheanteriorandleft-sidedshoulderofthedominantleftventricle.In
suchcircumstances,hadtheleftatrioventricularconnectionbeenformed,it


wouldlikelyhavebeenguardedbyatricuspidvalve.Acasecanbemade,
therefore,fordescribingtheentityas“tricuspidatresia,”despitethefactthatthe
leftatriumisblind-endinginthissetting,asitisintypicalmitralatresia
producedbyabsenceoftheleftatrioventricularconnection(seeFig.69.15B).
Irrespectiveofthenatureofthevalvethatmighthavebeenpresent,itisthe
arrangementofthepulmonaryvenousconnectionsandtheatrialseptumthat
largelydeterminestheclinicalpresentation.Forthesereasonswepreferto
distinguishthevariantsbydescribingabsenceoftheleftatrioventricular
connectionandspecifyingtheventricularmorphology,thusremovingany
potentialambiguity.Whenthevalvaratresiaistheconsequenceofabsenceofthe
left-orright-sidedatrioventricularconnection,themuscularflooroftheatrial
chamberisblind-ending.Itisseparatedfromtheventricularmassbythe
fibroadiposetissueoftheatrioventriculargroove(seeFig.69.14,right).Itused
tobethoughtthatthedimpleseenintheflooroftheblind-endingatrium(see
Figs.69.4and69.16)representedtheatreticatrioventricularvalve.Asshownin
Fig.69.4,inclassictricuspidatresiathedimpleoverliestheatrioventricular

componentofthemembranousseptum.Perforatingtheflooratthesiteofthe
dimpleproducesacommunicationwiththedominantleftventricleandnotthe
incompleterightventricle.Intheusualformoftricuspidatresia,theright
ventricleisincompletebecauseitlacksitsinletcomponent.Clinicalpresentation
inallformsofatrioventricularvalvaratresiaisinfluencedsignificantlybythe
ventriculoarterialconnectionsandthesizeoftheventricularseptaldefect,which
isalmostalwayspartofthelesion.Intricuspidatresia,theventriculoarterial
connectionsareusuallyconcordant.Theincompleterightventriclehasalong
infundibulumsupportingthepulmonarytrunk,whichspiralsaroundtheaortaas
itextendsintothemediastinum.Inaminorityofcases,theventriculoarterial
connectionsarediscordant.Thearterialtrunksareusuallyparallelastheymove
awayfromtheventricularmass.Parallelarterialtrunkscanrarelybefoundwhen
theventriculoarterialconnectionsareconcordant,withthiscombination
sometimesbeingdescribedasanatomicallycorrectedmalposition.Itisbetterto
considerthearrangementintermsofconcordantventriculoarterialconnections
withparallelarterialtrunks.Itisalsopossibletofindadoubleoutletfromeither
thedominantleftventricleortheincompleteleftventricle.Rarecaseshavebeen
describedwithacommonarterialtrunk.Pulmonaryatresiaisalsoapossibility.
Whentheventricularseptaldefectisrestrictiveandtheventriculoarterial
connectionsarediscordant,itisalsousualtofindeitheraorticcoarctation,or
interruptionoftheaorticarch.Thesefeaturesarealsotobeanticipatedwhen