Andersons pediatric cardiology 961
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totheotherlung,regardlessofthesystemicoxygensaturation,aneonatal
procedureisperformed.Specifically,iftheMAPCAsarefavorable,single-stage
completerepairisperformed(seeFig.36.15),butiftheMAPCAsare
unfavorable,theductusisstentedorasystemic-to-pulmonaryarteryshuntis
placedtotheduct-dependentpulmonaryarteryandthepatientisscheduledfor
unifocalizationandassessmentforintracardiacrepairat4to6monthsofage.
Hemodynamicinstability.
Iftheneonatalevaluationshowsasystemicoxygensaturationmorethan90%
withfailuretothrive,regardlessoftheanatomyofpulmonarybloodsupply,
completerepairisperformed,asthehighpulmonarybloodflowindicatesthat
thecirculationisadequatefortheperformanceofacompleterepairwithlow
resistance.Iftheneonatalsystemicoxygensaturationisbelow75%,neonatal
unifocalizationisperformedregardlessoftheanatomy,eitherwithorwithout
simultaneousrepairdependingonthestatusoftheMAPCAsandresultsofan
intraoperativepulmonaryflowstudy(seefurtheron).
AllOtherPatients(About85%ofPatients).
Otherwise,patientsareideallyscheduledforsurgeryat4to7monthsofage,
withaplantoperformcompleteunifocalization.Thisagerangerepresentsthe
idealtimewithrespecttominimizingmorbidity.Abovethisage,pulmonary
vascularobstructivediseasebecomesaconcern,potentiallyresultingis
unacceptablyhighpulmonaryarterypressureinunprotectedlungsegmentseven
afteranidealsurgicalresult.Belowthisage,significantairwayandpulmonary
morbidityismorecommonduetoimmaturetrachealandbronchialcartilage,
withaconcomitantlyhigherriskofprolongedhospitalization.Atthecomplete
unifocalizationprocedure,eitherintracardiacrepairwillalsobeperformed,
makingitasingle-stagecompleterepair,orintracardiacrepairwillnotbe
performedbutinsteadacentralsystemic-to-pulmonaryarteryshuntwillbe
placed.Atthetimeofunifocalization,adecisionismadeaboutproceedingwith
intracardiacrepair(i.e.,ventricularseptaldefectclosureandrightventricle-topulmonaryarteryconduitplacement)basedonthesizeofthepreoperative
physiologyandsizeofthepulmonaryvessels,andsometimesonthebasisofan
intraoperativeflowstudy,asdescribedpreviously37andfurtheron.Rarely,other
palliativeproceduresorvariationsmaybeperformed,includingstagedleftand
rightunifocalizationinthemostseverelyaffectedpatients.
Itcanbeusefultogrouppatientsaccordingtopatternofpulmonaryblood
supplytoanticipatethelikelyoperation.Thelargestgroup,patientswithlargecaliberMAPCAswithoutsegmentalstenoses,usuallyundergosingle-stage
completerepair.PatientswithsmallerMAPCAsandnosegmentalstenoses,20%
to25%ofthecohort,aretypicallyabletohavecompletesingle-stage
unifocalizationbutmayormaynotundergocompleterepairatthesame
operation.Patientswithextensivesegmentalstenoses,approximately10%of
patients,typicallyundergosingle-stageunifocalizationwithacentralshunt,
followedbycompleterepair6to12monthslater.Asnotedpreviously,asimilar
proportionofpatientshaveconfluentcentralpulmonaryarteriesthatarborize
completely,withdualsupplyMAPCAs,andareinitiallytreatedwithasurgical
aortopulmonarywindowintheneonatalperiod.
Althoughthisinitialstrategyisfollowedforpatientswithnativeanatomyat
ourinstitution,othersurgicalapproachesmayhavebeenusedinpatientsreferred
fromelsewhere.Althoughsuchpatientsmayhavereportedlyundergone“repair”
or“unifocalization,”theyoftenrequiresubstantialpulmonaryartery
reconstructionconsistingofaugmentation,unifocalizationofresidualMAPCAs,
and/orrevisionofpriorsurgicalanastomosisofMAPCAs.Occasionally,in
extremecases,stagedunifocalizationorpulmonaryarteryrehabilitationthrough
athoracotomymaybewarranted.
SurgicalTechniques
Unifocalization.
UnifocalizationandPAaugmentationproceduresareperformedthrougha
mediansternotomyundergeneralanesthesiawithstandardoperativepreparation.
Ifathymusispresent,itisresectedtoprovidefullexposuretotheupper
mediastinum.Theanteriorpericardiumisharvestedandtreatedwith
glutaraldehydeforuseastheventricularseptaldefectpatch.Bothpleuralspaces
areopenedanteriorandposteriortothephrenicnerve,andaseriesofstay
suturesareplaced1to2mmabovethephrenicnervetomarkitsposition.
Inspectionoftheheartshouldincludeasurveyofthecoronaryarteryanatomy.
Thedissectionisbegunbyidentifyingtherightandleftbranchpulmonary
arteries,whicharepresentinsome80%ofcases.Thesearetypicallyquite
diminutive,measuring1to3mmindiameter.Theplanebetweentheaortaand
mainpulmonaryarteryisdissectedtomobilizethepulmonaryarteriesfully.The
superiorvenacavaisdissectedcircumferentiallyandmobilizedfromthe
innominateveintothecavoatrialjunctiontofacilitateexposureofMAPCAsout
tothelungparenchyma.Tractionsuturesareplacedonthelateralborderofthe
aortaandonthesuperiorvenacava;theseareretractedlaterallytoopena
windowcraniadtotheleftatrium(Fig.36.17).Thetransversesinusisopened
widelytorevealthedescendingaorta,wherethemajorityofMAPCAsoriginate.
Theairwayisidentifiedandthesubcarinalspaceopened.Themanylymph
nodesinthisareaareresectedtofacilitateexposure.MAPCAsareidentifiedin
thissubcarinalwindowandcanbetracedproximallytotheirdescendingaortic
origins.Afterfindingthedescendingaorta,theoriginsoftheremaining
MAPCAscanbeidentifiedupanddowntheaorta.Retro-andintraesophageal
MAPCAs,whichwereobservedintwo-thirdsofpatientsinarecentstudyfrom
ourcenter,4shouldbesoughtonthelateralborderoftheaortaontheside
contralateraltotheaorticarch.Itisfrequentlynecessarytoremovethe
transesophagealechoprobetocompletethisdissection,particularlywhena
retroesophagealMAPCAispresent.Becausethemajorityofintraesophageal
MAPCAshavesignificantmidsegmentstenoses,theyshouldnotbeusedas
unalteredconduitsbutshouldeitherbetrimmeddistaltothestenosisor
augmentedwithapatch.DissectionofMAPCAsiscontinuedlaterallytothe
entranceintothelungparenchyma.Itisimportanttoperformthisdissection
priortotheadministrationofheparin,asdoingsoafterheparinizationcanleadto
intraparenchymalhemorrhage.Completehemostasisshouldbeobtained
throughouttheoperativefield,withparticularattentiontotheareasoflymph
noderesection.ThisdissectionexposesthefullcourseoftheMAPCAs,fromthe
origintothesegmentalbranchpointswithinthelungparenchyma,facilitating
appropriatereroutingduringunifocalization.MAPCAsfromheadandneck
vesselsaresimilarlyidentified,dissected,andcontrolled,proceedingfromthe
hilumorbytrackingtheMAPCArunningalongthetracheobronchialtree.
