Andersons pediatric cardiology 1147

Morphology
Bydefinition,theunifyingmorphologicabnormalityiscompleteobstructionof
theoutflowfromthemorphologicallyrightventricleinthepresenceofanintact
ventricularseptum.ThecavityoftheRVisusuallyhypoplastic,butitcanbe
grosslydilatedwhenthetricuspidvalveisincompetentoritsleafletsareabsent,
givingthe“wall-to-wall”heart.1Thislatterlesion,therefore,canbeconsidereda
variantofpulmonaryatresiawithintactventricularseptum,indeedoneofits
mostlethalforms.Itiscertainlyoneofthemostdifficulttotreat.Thisformof
thelesionisdiscussedinthischapter,eventhoughthecavityoftheRVis
dilated,alongwiththetricuspidvalvarorifice.Inthisregard,therehadbeena
vogueforconsideringtherightventricularcavityaseithersmallorlarge.33
Recognitionofthedegreeofcavitaryhypoplasiaproducedbymuralhypertrophy
isnowacceptedasthebestwayofassessingtheseverityofthe
malformation,34,35whileacceptingthatsomeindividualshavedilationoftheRV,
andthatpatientsshowingthelatterfeaturestendtohaveaverypoorprognosis
(Fig.43.2).ThelesionisaglobalconditionaffectingtheentiretyoftheRV.36–38
Theextentofmorphologicheterogeneityisillustratedbythefrequencyinwhich
eachanatomicfeatureoccurswithintheUnitedKingdomandIreland
population-basedstudy(Table43.1).39


FIG.43.2 Variationinsizeofthecavityoftherightventricleinthesetting
ofpulmonaryatresiawithintactventricularseptumassessedrelativetothe
sizeoftheleftventricleinthesameheart,andcomparedtosimilar
measurementsinnormalhearts.Themajorityofheartshavehypoplastic
cavities,withtheupperendoftheseoverlappingthespectrumofnormality.
Thosewithdilatedcavitiesareoutliersfromthespectrum.

Table43.1
PrincipalMorphologicFindingsofaUK/IrelandPopulation-Based
Study(1991–1995)

MorphologicFeature
Typeofpulmonaryatresia

Type
Membranous
Muscular
PartitestateoftheRV
Tripartite
Bipartite
Unipartite
Coronaryarterialabnormalities RV-to-coronaryfistulas
Coronaryarterialstenoses,interruptionandectasia
Ebsteinmalformation
SignificantRVdilatation
Sizeoftricuspidvalve
Medianz-score:echocardiograma
Medianz-score:autopsyb
SizeofRVinlet
Medianzscorea

N(%)
130/174(74.7)
44/174(25.3)
84/143(58.7)
48/143(33.6)
11/143(7.7)
60/132(45.5)
10/132(7.6)
18/183(9.8)
8/183(4.4)

−5.2(range,−18.3to9.4)
−1.6(range,−2.9to−0.4)
−5.1(range,−16.0to3.5)

az-Scorescalculatedfromechocardiographicallyderivednormalvalues,7ratherthan
bpostmortem-derivednormalvalues.77Inall,15abnormalitiesoftheleftventriclewere


documented,includingfourwithextremeseptalhypertrophywithbulgingintotheleftventricular
outflow.
RV,Rightventricle.
FromDaubeneyPE,DelanyDJ,AndersonRH,etal.Pulmonaryatresiawithintactventricular
septum:rangeofmorphologyinapopulation-basedstudy.JAmCollCardiol.2002;39:1670–
1679.

HypoplasticVentricularCavities
Inthosewithsmallventricles,thecavitaryhypoplasiaisduetomural
hypertrophy.First,thethickenedwallssqueezeouttheapicaltrabecular
componentoftheventricle.Then,withongoinghypertrophy,theoutletis
obliterated.Eventually,therefore,theinletistheonlyeffectivecavityinthose
withthesmallestRVs.36Ifdescribingthisspectrumintermsof“unipartite”and
“bipartite”ventricles,itshouldberememberedthatallthreeventricular
componentsarepresentinallcases.Thekeytoappropriateinterpretationis
recognitionthattheincreasingmuscularhypertrophysqueezesoutthedifferent
partsoftheRVcavity.40Inthosewiththeleastseverelyaffectedhearts,
therefore,allthreepartsoftheventricularcavityarewellformed,withminimal
muralhypertrophy(Fig.43.3).

FIG.43.3 Left,Heartwiththeparietalwalloftherightventricleremoved;
thepulmonaryvalveisimperforate,butallthreepartsoftheventricular