Andersons pediatric cardiology 687

SurgicalConsiderations
Amajority,upto85%insomeseries,ofthosewithisomerismwillrequire
functionallyuniventricularpalliation.Thoseinwhomabiventricularrepairis
feasiblearemorelikelyhaveleftisomerism.Forthoserequiringfunctionally
univentricularpalliation,neonatalinterventionsmayberequired.Thismaybein
theformofapulmonaryarterybanding,anaortopulmonaryshunt,oraNorwood
proceduredependingonthespecificsontheanatomyandthebalanceof
systemicandpulmonarybloodflow.Somewhowillundergofunctionally
univentricularpalliationmaynotrequireanyneonatalinterventioniftheyhave
relativelybalancedcirculations,whichmaybethecaseinthesettingofdoubleoutletright(orsolitary)ventriclewithsubpulmonarystenosis.Thesepatients
maybefunctionallybanded,maintainingreasonablerelativesystemicand
pulmonarybloodflow.
Thesecondstageoffunctionallyuniventricularpalliationwillconsistofa
GlennorKawashimaprocedure.Bothoftheseproceduresconsistofasuperior
cavopulmonaryanastomosiswiththedifferencebeingprimarilyfunctionalbased
ontheunderlyinganatomy.Thosewithaninterruptedinferiorcavalveinthat
drainsintothesuperiorcavalveinviaanazygosorhemiazygosveinthat
undergoesasuperiorcavopulmonaryanastomosisaresaidtoundergoa
Kawashimaprocedure.Thispresentsanimportantdifferenceasalarger
proportionofthesystemicvenousreturnnowreturnsdirectlytothepulmonary
circulationinapassivemannerwhencomparedtotheGlenn.Aftera
Kawashimaprocedure,theonlysystemicvenousreturndirectlytotheheartis
likelyhepaticvenousreturnwhileafteraGlennproceduretheinferiorcavaland
hepaticvenousflowremain,returningdirectlytotheheart.Approximately85%
ofthesystemicvenousreturnisredirectedintothepulmonarycirculationaftera
Kawashimaprocedure.
Withalargerproportionofbloodflowbeingredirecteddirectlytothe
pulmonarycirculationatonce,thereisconcernthatpatientsmayfairworsein
thepostoperativeperiodafteraKawashimaprocedurewhencomparedtoa
Glennanastomosis,althoughinthemodernerathisdoesnotappeartobethe
case.Ifdonetooearlyinlife,however,eitherformofsuperiorcavopulmonary

anastomosiscouldbepoorlytolerated.Anecdotally,patientsundergoingthe
Kawashimaprocedurebetween3and6monthsoflifetoleratetheprocedure
well,althoughwaitingbeyondthisperiodwillallowforadditionalpulmonary


arterialgrowth,pulmonaryvascularmaturation,andpulmonaryvascular
resistancedecrease.
Astudyincludingslightlyover5000patientsundergoingthesuperior
cavopulmonaryanastomosis,ofwhich450hadisomerism,revealedthatthe
medianageofthosehavingtheGlennprocedurewas10monthsinthosewithout
isomerism,comparedto13monthsinthosewithisomerism.Medianlengthof
admissionforbothgroupswas8days,andmediancostofhospitalizationdidnot
differ.Theneedforextracorporealmembraneoxygenationalsodidnotdiffer
betweenthetwogroups,withapproximately1%requiringextracorporeal
membraneoxygenation.Inpatientmortalitywasalsocomparablebetweenthe
twogroups,witha2.4%inpatientmortalityinthosewithisomerism.50
Thereareuniqueissuesthatsometimesarisewiththesuperiorcavopulmonary
anastomosisinthosewithisomerismduetothefrequentfindingofsystemic
venousanomalies.Ofparticularnoteisthesituationinwherebilateralsuperior
cavalveinsarepresent.Inthissituation,oncebilateralsuperiorcavopulmonary
anastomoseshavebeenconstructed,theportionofthepulmonaryarteriesthatlie
betweenthetwosuperiorcavalveinsmayreceivelimitedflowandthusbecome
hypoplastic,atretic,andevendiscontinuous.Somegroupshavetriedtoreduce
theriskofthisbycreatingaV-shapedsuperiorcavopulmonaryanastomoses.In
thisconfiguration,theendsofthesuperiorcavalveinsareanastomosedtothe
pulmonaryarteriessuchthattheanastomosesareadjacenttoeachother.Thishas
demonstratedsomebenefitinpreservationofthepulmonaryarteries.51
Thethirdstageofpalliationforthoseundergoingfunctionallyuniventricular
repairconsistsofaninferiorcavopulmonaryanastomosis,orFontanprocedure.
Forthosewithaninferiorcavalveinreturningdirectlytotheheart,theFontan

conversionconsistsofthetraditionalinferiorcavopulmonaryanastomosis.For
thosewithaninterruptedinferiorcavalvein,however,theFontanconversion
involvesonlythehepaticveins.ConversiontotheFontancirculationshouldbe
doneinbothpatientswhohaveundergoneaGlennanastomosisoraKawashima
procedure.TherationaleforFontancompletionisthesameinbothgroups.The
firstaimistofurthernormalizesaturations,withthesecondaimbeingtoallow
forthehypotheticalhepaticfactortoenterthepulmonarycirculation.Theissue
ofthehepaticfactorreachingthepulmonarycirculationisofparticular
importance,astheagent,whateveritis,helpspromoteregressionofand/or
preventtheformationofpulmonaryarteriovenousmalformations.
Theissueofpulmonaryarteriovenousmalformationsisonethatisof
particularinterestinthosewithisomerism,particularlythosewithleftisomerism


whohaveundergoneaKawashimaprocedure.Nearlyathirdofthesepatients
willdeveloppulmonaryarteriovenousmalformations,experiencingfurther
desaturationasaresult.Catheterizationandbubbleechocardiographycanhelp
makethediagnosisofsuchpulmonaryarteriovenousmalformations.Pulmonary
arteriovenousmalformationsgenerallydevelopinthefirst30monthsafterthe
Kawashimaprocedure.Saturationswillfallfromthemidtohigh80%range
immediatelyaftertheproceduretoapproximatelythemidtohigh70%rangedue
tothedevelopmentofthepulmonaryarteriovenousmalformations.Agreater
degreeofdesaturationmaybenoted,withrarecasesofpatientshaving
saturationsinthe50%rangeand60%range.Inamajorityofpatients,
completionoftheFontancircuitwillleadtoatleastpartialresolutionof
pulmonaryarteriovenousmalformations,withsaturationsgenerallyreaching
approximately90%within1monthofcompletioninmostpatients.52–54
Unpublisheddatahavedemonstratedthatisomerismdoesindependently
increasethelengthandcostofadmissionfortheconversiontotheFontan
circulation.Thepresenceofisomerismindependentlyincreasedthelengthof

admissionbyapproximately1.6daysandincreasedthetotalchargesforthe
admissionby$31,000.Needforextracorporealoxygenationandinpatient
mortalityduringtheadmissiondidnotdifferbetweenthosewithandwithout
isomerism.Inpatientmortalityinthosewithisomerismwas3%.
Competitiveflowinthepulmonarycirculationfromthevarioussystemic
venousreturnscangreatlyimpactdistributionofbloodflowaftercompletionof
theFontancirculation.Insomeinstances,thismaydirectamajorityofthe
hepaticvenousflowtoasinglelung,leadingtounilateralpulmonary
arteriovenousmalformations.Somegroupshavetriedtomodelflowsusingdata
frommagneticresonanceimaging.Thesedatacanbeusedtosimulatehow
bloodwillflowthroughthecircuitwithavarietyofdifferentgeometries.Of
particularinteresthasbeentheY-graft,inwhichasinglelimbbifurcatesintotwo
separatelimbs,whichanastomoseintothepulmonaryarteries.Thishasbeen
demonstratedtohavelesserpowerlossthroughtheFontancircuit,andimprove
hepaticflowdistributionincomputermodelingstudies,buthasnotshown
similarresultsinthelimitedclinicalstudies.Y-graftsaremoretechnically
demandingandmayalsobepronetothrombus.SuchY-graftsmaybehelpfulin
selectpatients,particularlyinthesettingofdiscontinuouspulmonary
arteries.55–67InadditiontotheY-graft,othergeometrieshavebeendeveloped
andhaveshownbenefitinspecificpatients.Directanastomosisofthehepatic
veinsintotheazygosveininthosewithaninterruptedinferiorcavalveinhas