Andersons pediatric cardiology 1126

“suiciderightventricle.”Carefulattentiontoanesthesia,thepreoperativestateof
hydration,anduseofβ-blockadewillusuallybesufficienttomanagetheacute
rightventricularoutflowtractreactivity.95Residualrightventricularsubvalvar
narrowingwillusuallysettleovertime.
Iftheprocedureissuccessfulintermsofrightventricularpressureand
transvalvargradient,thenarightventricularangiogramisusuallyobtained.The
investigationspriortodischargearecompletedwithechocardiographytoassess
thedegreeofpulmonaryincompetenceandtheintegrityofthetricuspidvalve.
Outsideoftheneonatalperiod,itisusuallypossibletoperformtheseprocedures
asdaycases.
Patientswithdysplasticpulmonaryvalves,inparticularthosewithNoonan
syndrome,aremorelikelytoretainasignificantresidualgradientafterballoon
pulmonaryvalvuloplasty.Whereasinthepastthesepatientswereoftenreferred
forsurgicaltherapy,theavailabilityoftranscatheterpulmonaryvalve
implantationhasprovidedanadditionaltreatmentalternativethatshouldbe
consideredinselectedpatients.68

SevereorCriticalNeonatalPulmonaryStenosis
Thepresentationandmanagementofcriticalpulmonarystenosisintheneonatal
perioddeservesspecialdiscussion(seeFig.42.33).Infantsmaypresentina
criticallyillstate,withcyanosisasaresultofright-to-leftshuntingacrossthe
atrialseptumandbeingdependentonpatencyofthearterialductforsurvival.
Theefficacyofballoondilationofthepulmonaryvalvedependsnotjustonthe
resultofthevalvotomybutalsoonthesizeandcomplianceoftherightventricle,
tricuspidvalve,andtheventriculoarterialjunction.96Thusthesizeofthe
structuresintherightheartmustbeevaluatedaspartofthemanagement.Inthis
context,criticalpulmonaryvalvestenosisissomewhatsimilartopulmonary
atresiawithintactventricularseptum,eventhoughthechancesofrequiring
reinterventionarehigherinpatientswithpulmonaryatresiaandintactventricular
septumthaninthosewithcriticalpulmonaryvalvestenosis.97–99
Relativehypoplasiaoftherightheartstructuresitselfisnotacontraindication

forballoondilationofthepulmonaryvalve;indeed,follow-upstudieshave
shownthattherateofgrowthoftherightheartcanexceedtherateofsomatic
growthaftersuccessfulballoondilation.96,100,101Immediatelyfollowingballoon
dilation,despiteadequateopeningofthepulmonaryvalve,itmaystillbe
difficulttoseparateinfantsfrominfusionsofprostaglandin.Thisismostlikelya


resultofhypertrophyanddiastolicdysfunctionoftherightventricle,favoringa
cyanoticshuntacrosstheatrialseptum.Persistenthypoxemiamaysettleovera
fewdaysastherightventriclerecovers.Shouldhypoxemiapersist,itmaybe
necessarytoestablishanalternativesourceofsupplyofbloodtothelungs,such
asasystemic-to-pulmonaryarterialshuntorstentingofthearterialduct.A
detailedanalysisofthemorphologyoftherightheartstructuresmayhelppredict
whetheranalternativesourceofsuchflowisgoingtoberequired,eventhough
firmpredictionsaredifficultinmostpatients.Adiameterofthetricuspidvalvar
orificeofgreaterthan11mm,rightventricularvolumesofgreaterthan30
mL/m2,anddimensionofthepulmonaryvalveofgreaterthan7mmappearto
stratifypatientswhoarelesslikelytorequireaninterventiontoincrease
pulmonaryflow.102FurtherdetailsarediscussedinChapter43(pulmonary
atresiawithintactventricularseptum).
Fromatechnicalstandpoint,keepingthewirepositionedacrossthe
pulmonaryvalveuntilitisdecidedwhetherupsizingoftheballoonisrequiredis
importantinthesepatients.Therightventricularoutflowtractinneonatesisvery
sensitiveandoftencathetermanipulationcanleadtoafurtherincreasein
subpulmonarynarrowingthatisoftentemporarilypresentinthesepatients.If
wirepositionislost,attemptsatrecrossingtherightventricularoutflowtractcan
bedifficultandassociatedwitharrhythmiasandhemodynamicinstability.For
thesamereason,inpatientswithmarkedinfundibularnarrowingafterballoon
pulmonicvalvuloplasty(seeFig.42.33),commencingthepatientonpropranolol
forashortperiodoftimemaybebeneficial.

FetalBalloonPulmonaryValvuloplasty
Fetalpulmonaryballoonvalvuloplastyhasbeenperformedinselectedpatients
withpulmonaryatresiaandintactventricularseptuminthehopetoaidright
ventriculargrowthanddevelopment,thusallowingpatientstoprogress
postnatallythroughabiventricularpathway.36,103,104Atthisstage,however,
interventionsarenotyetperformedforseverelystenoticvalves(ratherthan
pulmonaryatresia).Inthiscontextsomestudieshaveattemptedtoidentifyfetal
parametersthatmaypredictanonbiventricularversusabiventricularoutcome,
whichincludeatricuspid/mitralvalveratiobelow0.7,right/leftventricular
lengthratiolessthan0.6,tricuspidvalveinflowdurationbelow31.5%ofcardiac
cyclelength,andthepresenceofsinusoidsintherightventricle.105Astudyby
Kawazuandcolleaguesusedatricuspidvalvediametertototalcardiac


dimensionratioofgreaterthan0.21asacutoffforultimatebiventricular
repair.106Alltheseparametersmaybehelpfulinselectingtheappropriate
patientsforfetalintervention.However,overallresultsoffetalinterventionsdo
notyetsupportwidespreadadoptionofthetechnique,andatthisstagethe
techniqueshouldbeemployedonlybyalimitednumberofcentersinselected
patientsaspartofaresearchprotocol.103

MultipleBalloonTechniques
Usingtherecommendedsizingofballoonsof120%to125%ofthedimensionof
thepulmonaryvalve,itisclearthatlargeballoonswillberequiredfor
adolescentsandadults.Suchballoonsmaybedifficulttosource,andthe
frequencyofusemightmakeitimpracticabletokeeptheseitemsinstockinthe
pediatriccatheterizationlaboratory.Furthermore,inthepast,themaximum
inflationpressureoflargerballoonswaslimited,andanadvantageofusingtwo
smallerballoonswastheabilitytoobtainhigherinflationpressureswhen

needed.
Techniquesusinganadditionalballoonangioplastycatheterthroughan
additionalvenouspunctureandoveranadditionalguidewirehavebeenreported
(Fig.42.34;Videos42.6and42.7).71,107–109Theeffectivedimensionofthe
double-balloontechniqueiscalculatedthus110: