Andersons pediatric cardiology 368
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stenosis,techniquesincludecommissurotomy,valvoplasty,cordalfenestration,
andsplittingofpapillarymuscles.Formitralinsufficiency,techniquesinclude
repairofclefts,resection,shorteningoraugmentationofleaflets,cordal
shortening,annuloplasty,andcreationofadoubleorifice.161Ingeneral,
mortalityislowwithrepairinthesettingofbiventricularcirculations.161–164In
thosewithafunctionallyuniventricularcirculation,incontrast,repaircarriesa
highermortality.158
Repairoftheaorticvalveislesswellacceptedthanthatofthemitralvalve,
albeitexperienceisaccumulating.165–171Overthelastdecade,experienceand
successwithrepairhaveimproved.169–172Techniquesincluderepairofvalvar
perforations,suspensionofprolapsedleaflets,annuloplasty,andextensionof
leafletswithpericardium.158Inparticular,extensionoftheleafletshasbeenused
withsuccessinpatientswithrheumaticaorticvalvedisease,with90%of
patientsfreefromvalvarrelatedcomplicationsat7years.Extensionhasalso
beenappliedtopatientswithcongenitalpathologywithimprovingresults.173,174
MorecontemporaryapproachestoaorticvalverepairincludetheOzaki
technique.Thisapproachreliesontheuseofautologouspericardiumto
constructastentlessbioprostheticvalveintheoperatingroomafterexcisionof
thenativeaorticvalve.Ithasbeenappliedtoawidevarietyofaorticvalve
morphology.Inaseriesofover400reconstructions,thefreedomfrom
reoperationwas96.2%at4yearsoffollow-up,andthemeanresidualgradient
was13.8±3.5mmHg.175
StrategiesforCardiopulmonaryBypass
andPerfusion
Surgicalinterventioninsidetheheartoronthegreatvesselsnormallyrequires
significantinterruptionofflowofbloodinregionsofthesurgicalfieldto
achieveadequatevisualization(Video16.1).Topermitamorecontrolled
surgicalapproach,extracorporealcirculationandgasexchangewasdeveloped
andfirstusedsuccessfullyintheearly1950s.176,177DuringCPB,venousblood
fromthegreatveinsorrightatriumisdivertedtoanartificiallungandthen
reinfusedintosystemicartery,mostcommonlytheaorta.Avarietyofspecific
techniquesareusedforcannulationandperfusion.Theseareintendedtodeliver
bloodfromwhichcarbondioxidehasbeenremovedandoxygenaddedintothe
patientataratesufficienttofullysupportthefunctionofthebodilyorgansfor
thedurationofthesurgicalrepair.Suchtechniqueshavepermittedthe
developmentofextraordinarysurgicalreconstructiveprocedures.Optimal
strategypermitsextensivesurgicalintervention,withlargelypredictablefreedom
frompermanentinjurytotheorgans.Plannedandunplannedmodificationsof
techniques,however,mayplaceorgansattheriskofischemia.178,179
Additionally,thenatureoftheinteractionsofbloodwithartificialsurfaces,the
effectsofassociatedalterationsintemperature,andnonpulsatileperfusion
duringbypassmakethetechniqueapathwayfordirectinflammatoryand
ischemicinjury.180
CircuitryofCardiopulmonaryBypass
OnetaskoftheperfusionististotailortheCPBcircuittothespecificneedsof
theindividualpatient.Thevariabilityofsize,anatomy,andpathophysiology
necessitatestheuseofagreatnumberofproducts.Largeextracorporealsurface
areasandprimevolumeshavebeenidentifiedaspotentialcontributorsto
complicationsfollowingCPB.181Multiplesizesofoxygenators,heat
exchangers,reservoirs,andothercomponentshavebeendesignedtoaddress
theseissues.Muchoftheresearchanddevelopmentforthechildhasfocusedon
reductioninsurfacearea,primevolume,andbiologicincompatibility.182,183
Itisadvisableforthecircuitsatagiveninstitutiontobeorganizedinthesame
manner,facilitatingtheabilityofperfusioniststoprovidesafeandconsistent
servicetoallpatients.Acommonconfigurationforbypassistousebicaval
cannulationwithasinglevenouslinefordrainageintoahard-shellvenous
reservoirwithanintegratedcardiotomyreservoir(Fig.16.13).Atypicalstrategy
foracardiaccannulationisshowninFig.16.14.Arollerpumpisusedtopump
deoxygenatedbloodfromthereservoirthroughahollowfiberoxygenatorwith
anintegratedheatexchangerandfilter.Bloodexitingtheoxygenatorreturnsto
thepatientviathearterialcannulaplacedintheascendingaorta.
FIG.16.13 Simplifiedschematicofthecomponentsofatypical
cardiopulmonarybypasscircuit.Arollerpump,anoxygenator,aheat
exchanger,avenousreservoir,andafilterareincluded.IVC,Inferiorcaval
vein;SVC,superiorcavalvein.
