Andersons pediatric cardiology 1154
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ofmuscularatresia.54Today,cardiaccatheterizationisoftenthepreludetoan
interventionalapproachtomanagement,undertakenatthesamecatheterization.
OtherImagingModalities
Therehasbeenrapiddevelopmentandapplicationofcardiacmagnetic
resonanceandcomputerizedtomographicimagingoverthepastdecade.Both
offernoninvasivealternativestocardiaccatheterizationandangiographyand
mayultimatelysupplantsuchinvasivetechniques.66Theybothprovideexcellent
three-dimensionalanatomicimagingofthecardiovascularsystem.Computed
tomographyisparticularlyhelpfulintheneonatalperiodandcanbeusedasa
preludetocatheterizationorsurgicalintervention(seeFig.43.4).Cardiac
magneticresonanceimaginghasanimportantroleinsurgicalplanningbeyond
infancy,particularlyinthosepatientsundergoingGlennandtotalcavopulmonary
connectionforuniventricularpalliation.Thisimagingmodalitycanbeusedto
defineanatomyandventricularfunction,butalsotoquantifysystemic-topulmonarycollateralflow,whichisassociatedwithprolongedpleuraleffusion
andhospitalstayaftertotalcavopulmonaryconnection.67
Inlatefollow-upcomputedtomographyoffersfastacquisitionwithexcellent
delineationofstructure,butitislimitedbyionizingradiationexposureandlacks
multiparametricimagingcapacity.
HemodynamicsandPhysiology
Systemicvenousreturntotherightatriumisnormal(seeFig.43.1).Theflow
prenatallywastotheleftatriumthroughapatentovalforamen,andtotheleft
heart,continuingretrogradelyviathearterialductintothepulmonaryarteries.
Thiscontinuesafterbirthuntilclosureoftheduct.Theincreasedpulmonary
venousreturntotheleftatriummayreducethesizeoftheforamen,whichis
particularlyimportantafterconstructionofasystemic-to-pulmonaryarterial
shuntbecausetherestrictiveforamenmayneedtobeenlargedusingballoon
atrialseptostomy.55
Whenthetricuspidvalveishypoplastic,itsopeningmaybelimited
anatomically,butalsofunctionallybyhighfillingpressures.Theright
ventricularpressurewillbesuprasystemic.EgressofbloodfromtheRVisvia
lowvolume,buthighvelocity,tricuspidregurgitationand/orventriculocoronary
arterialconnectionsintotheaortaduringsystole.Therecanberetrogradefilling
oftheRVfromthecoronaryarteriesduringdiastole.Rightventricularsystolic
pressurescancausehighshearstresstothecoronaryarterialwalls,leadingto
stenosesandRV-dependentcoronaryarterialcirculation.Inthesecircumstances,
alterationofthebalanceofrightventricularandaorticdiastolicpressurescan
leadtomyocardialinfarction.Hence,rightventriculardecompressionshouldbe
avoidedwheneverthereisRV-dependentcoronaryarterialcirculation.Caution
shouldbeusedwhencreatingasystemic-to-pulmonaryarterialshunt,andcare
shouldbetakentoligatethearterialducttopreventanydisastrousfallsinthe
diastolicbloodpressures.68
Leftventricularfunctioncanalsobeaffected,andithasbeensuggestedthat
theleftventriclemayultimatelybethelimitingfactorinthisdisease.35,69,70
Long-termhemodynamiceffectsusuallyreflectresiduallesions.Biventricular
circulationmaybecomplicatedbythelong-termeffectsofresidualpulmonary
stenosis,regurgitation,andtricuspidregurgitation.Thefunctionally
univentricularcirculationmaybecomplicatedbythelong-termeffectsofhigh
venouspressure,rightatrialdilation,andcoronaryarterialstenoses.
Incompletelyseparatedcirculationsmaysuffertheadditionallong-termeffects
ofcyanosisandparadoxicemboli.66
TherapeuticOptions
HistoricalPerspective
Bythemid-1950s,pulmonaryvalvotomyhadbeenproposedasanappropriate
treatmentwhentheRVwasofgoodsize.33,71Itwasalsosuggestedthata
systemic-to-pulmonaryarterialshuntbeperformedwhentheRVwassmall.33
ThefirstreportsofsuccessfulsurgerycamefromtheMayoClinic,the
UniversityofMinnesota,andtheHenryFordHospital.33,72,73
Thecombinationofrepairoftherightventricularoutflowtractand
constructionofasystemic-to-pulmonaryarterialshuntwasfirstreportedin
1971.74Thesetechniquesarestillthemainstayofsurgicalinterventionstoday,
buttheindicationsforeachhavebeenconsiderablyrefinedasourknowledgeof
themorphologiccomplexitieshavegrown.
Successfulpercutaneousperforationoftheatreticpulmonaryvalvewitha
catheterwasfirstreportedin1991,usingaguidewire,75laserenergy,76,77or
radiofrequencyenergy.78,79Thisapproachhasnowbecomethetreatmentof
choiceinmanycentersforpatientswithagood-sizedRVandanatreticvalvar
membrane.
ContemporaryApproaches
FetalIntervention
Fetalinterventionisnowareality,althoughitsrateofsuccessatpresentislow,
anditmuststillbeconsideredanexperimentaltechnique.80–83Itsrolein
managementisstillbeingexplored.
PostnatalIntervention
Becausethelesionisductdependent,aninfusionofprostaglandiniscommenced
afterdiagnosis,andthebabytransferredtoacardiacunit.Theinvestigations
discussedpreviouslyareperformedtoidentifytheuniqueconstellationof
morphologicfeatures.Thelong-termgoalofinterventionistoseparatethe
pulmonaryandsystemiccirculations.Theinvestigations,therefore,aredirected
toascertainwhetherthiscanbeachievedbycreatingbiventricularor
