Andersons pediatric cardiology 1863

FIG.71.12 ThelateraltunnelFontanconstructedafterapriorhemiFontan.(A)Thefunctioninghemi-Fontanshowingtheintactpatchbetween
thesuperiorcavopulmonaryanastomosisandtherightatrium.(B)An
atriotomyisperformedandthepatchbetweenthesuperiorcavopulmonary
anastomosisandtherightatriumisexcised.(C)Abafflecreatedbyincising
atubegraftlongitudinallyissewninplacetodirectbloodfromtheinferior
cavalveintothepulmonaryarteries.(FromJacobsML,Pourmoghadam
KK.Thehemi-Fontanoperation.SeminThoracCardiovascSurgPediatr
CardSurgAnnu.2003;6:90–97.)

PotentialadvantagesofthelateraltunnelFontanincludegrowthpotentialand
easeoffenestration.Computationalfluiddynamicstudiessuggestbetter
efficiencywithlowerenergyloss.268Thedisadvantagesofthelateraltunnel
includetheneedforaorticcrossclampingandtheinclusionofprosthetic
(potentiallythrombogenic)materialexposedtothepulmonaryvenousatrium,
whichcouldincreasetheriskofstrokeandsinusnodedysfunction.Incontrast,
theextracardiacFontanmayhavelessarrhythmias,doesnotrequirecross
clamping,and,withidealanatomy,canevenbedonewithoutcardiopulmonary
bypass.Thedisadvantagesincludethelackofgrowthpotential,neointimal
proliferationwithobstruction,andthrombusformation.Largesingle-center
seriesshowcomparableoutcomeswithbothtypesofcompletion


Fontan.256,269–276Thechoiceappearstobelargelyinstitutional,althoughthe
extracardiacFontanappearstobegaininginpopularityduetoeaseof
constructionandapplicationtoawidevarietyofanatomicvariations.
OneareawheretheextracardiacFontanhasbeenwidelyappliedisinthe
settingofapicocavaljuxtaposition.Thisoccurswhentheapexoftheventricular
masssitsovertheipsilateralentranceoftheinferiorcavalveinintotheatrium
ratherthanthemoretypicalsituationinwhichtheapexpointscontralateralto
theinferiorcavalvein.AmongpatientswithfUVHthiscancomplicate
constructionoftheFontan.Thechoiceiswhethertobringtheconduitalongthe

shortestroute,behindtheventricularmass,whichriskscompressionofthe
conduit,ortobringtheconduitacrossthemidline,overthevertebral
column.277–280Athirdoptionistheintra/extracardiacFontan,whichmaybe
suitabletocomplexincludingapicocavaljuxtaposition(Fig.71.13).Withthis
approach,throughanatriotomy,aconduitisanastomosedtotheentranceofthe
inferiorcavalvein.Theconduitrunsthroughtheatriumbeforeexitingtheroof
andcontinuingtothepulmonaryarteries.212Thistechniquecanbeappliedtoa
widevarietyofanatomicvariationsandafenestrationtocreatewithinthe
intraatrialportionoftheconduitisstraightforward.

FIG.71.13 Intra/extracardiacFontan.(A)Anatriotomyiscreatedaway
fromthesinusnode.(B)Atubegraftisanastomosedtotheinferiorcaval
veinorifice.Afenestrationiscreatedinthetubegraftthatwillbecontained
intheatrium.Thetubegraftexitstheatriumviatheatriotomy,whichisthen
sewntothegrafttoclosetheatrium.(C)Thecephaladendofthegraftis
thenanastomosedtothepulmonaryarteries.ePTFE,Expanded
polytetrafluoroethylene.(FromJonasRA.Theintra/extracardiacconduit.
SeminThoracCardiovascSurgPediatrCardSurgAnnu.2011;14:11–18.)


AfenestrationisanintentionaldefectcreatedwithintheFontanpathwaythat
connectsittothepulmonaryvenousatrium.Thefenestrationwillshuntrightto
left,loweringcentralvenouspressureandaugmentingventricularpreload,albeit
attheexpenseofsomedegreeofdesaturation.Asaconsequenceofsurgeryand
cardiopulmonarybypass,allpatientsintheearlypostoperativeperiodwill
experienceatransientperiodofincreasedPVR.Afenestrationmaybemost
beneficialintheearlypostoperativeperiod.Thecombinationoflowercentral
venouspressureandincreasedventricularpreloadwillimprovesystemicoutput
andthelowercentralvenouspressure,reducinghydraulicfactorsleadingto
persistentpleuraleffusions.Inarandomizedcontrolledtrial,theuseofa

fenestrationresultedinshorterdurationofchesttubeoutputandhospitallength
ofstay.281Apersistentfenestrationhasriskandbenefits.Inadditionto
incompletereliefofhypoxemia,afenestrationcanresultinparadoxicembolism
andstroke,althoughthereareasyetinsufficientdatatosuggestthatfenestration
closurereducesstrokeriskinthispatientpopulation.282–284Fenestrationhas
beenusedasastrategytomanagelatecomplicationsoftheFontan,including
protein-losingenteropathyandplasticbronchitis;thereforeapersistent
fenestrationmaybeworthmaintaining.Inaretrospectiveanalysis,fenestration
closurewasassociatedwithimprovedsaturationbutnotimprovedevent-free
survival.285

DecisionMaking:WhenIsItSafetoLeavethe
OperatingRoom?
AtthecompletionofanuncomplicatedFontanprocedure,centralvenous
pressurewillbeelevatedinthehighteensandsaturationsshouldbegreaterthan
90%inthosepatientswithoutafenestrationandgreaterthan80%amongthose
withafenestration.Priortoweaningfromcardiopulmonarybypass,theteam
shouldmakecertainthatventilationissatisfactoryandthatelectrolytes,
particularlycalcium,havebeennormalized.Lowtomoderateinotropicsupport
iscommonandmilrinoneiscommonlyusedasafirst-lineinotropicagentdueto
itspulmonaryvasodilatoryaction.Transesophagealechoshouldbeperformed
priortoweaningfrombypasstomakecertainthatde-airingiscompleteandafter
weaningfrombypasstomakecertainthatventricularfunctionissatisfactoryand
thatanyresidualAVvalveregurgitationisacceptable.Lowcardiacoutputinthe
faceofanelevatedcentralvenouspressuresuggestsaproblemwiththeFontan
pathwayoranelevationofPVR.Thepulmonaryvenousatrialpressurecanbe