Andersons pediatric cardiology 367
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FIG.16.11 TheMelodyvalveisabovinejugularvein–valvedconduit(A)
placedwithinaballoon-expandablestent(B)andwasdesignedfor
catheter-basedpulmonaryvalvereplacement.Ithasbeenusedformitral
valvereplacementininfantsandchildren.(C)Theprosthesisismodifiedby
placingapericardialskirttoallowfixationwithinthemitralannulus.The
valvecanbeseriallydilatedtoaccommodategrowth.
Forreconstructionoftherightventricularoutflowtract,biologicvalves,
includinghomograftvalvedconduitsandxenobioprostheticvalves,aremost
commonlyused.Biologicvalveshavelongerdurabilityinthelowerpressured
pulmonarypositioncomparedtoanypositioninthesystemiccircuit,favoring
theuseofbiologicovermechanicalvalves.Furthermore,theriskof
anticoagulationisavoided.Homograftconduitshaveexcellenthandling
qualities,conformtotheanatomy,andfacilitateachievementofhemostasis.
Limiteddurability,however,canbeaproblem.Earlyvalvarinsufficiencyand
obstructionhavebeenreported.136–138Insomechildren,homograftsundergo
severecalcification,withaccompanyingshrinkage,thatcanresultinobstruction.
Calcificationappearstobemoreacceleratedinyoungerchildren.137,139–141
Immunologicincompatibilitybetweendonorandrecipienthavebeenproposed
ascontributingfactorstothiscalcificationandfailureofthegraft.139,142–144
Analternativetohomograftsisuseofthebovinejugularvenousconduit
(Contegra,Medtronic)(Fig.16.12).TheContegragrafthasbeenusedin
reconstructionoftheoutflowtractinpatientswithcommonarterialtrunk,
tetralogyofFallot,theRossprocedure,andpulmonaryatresia.145–149Earlyand
mid-termhemodynamicresultsarefavorable,150withonestudyshowingvalvar
regurgitationtobeabsentinalmosthalfofpatientsatameanfollow-upof26
months.147Inoneofthelargestseries,withameanfollow-upof2.1years,there
wasnorelevantgradientdetectedatthelevelofthevalvesandminimalvalvar
insufficiency.150InaprospectivemulticenterstudyconductedbytheCongenital
CardiacSurgeon'sSociety,thebovinejugularveinfaredwell,withalower
probabilityofprogressingtomoresevereformsofsevereregurgitationthan
othertypesofconduit.150,151Bovinejugularveinconduitsaresusceptibleto
aneurysmaldilatation,aparticulartendencyfordistalstenosis,andanincreased
riskofendocarditis.136,146,152,153
FIG.16.12 (A)Bovinejugularveingraft.Notethetricuspidvenousvalve.
(B)Thevalveiscontainedwithinalengthofjugularveinthatcanbe
tailoredtothespecificanatomicrequirementsofthepatient.(Courtesy
Medtronic,Inc.,Minneapolis,MN.)
Theuseofsmallconduitsisnotsurprisinglyariskfactorforfailure,149,154but
interestingly,oversizingthevalvebymorethanazscoreof2.7hasalsobeen
showntobeariskfactorforearlyfailure.154Thistrendwasconfirmedinthe
studycoordinatedbytheSocietyofCongenitalHeartSurgeons,whereoutcomes
werebetterwhensizeswithzscoresbetween1and3werechosen.152Thereis
generalagreementthatabioprostheticvalveisthebestoptioninthetricuspid
positionwhenthenativevalvecannotberepaired.155Bioprostheticvalves
appeartofairbetterinthispositionthaninanyotherposition.Thefreedoms
fromreoperationisreportedtobe97.5%±1.9%and80.6%±7.6%at1and5
years,respectively.
Catheter-deliveredbioprostheticvalvesplacedwithinexpandablestentsare
increasinglyusedforreinterventionontherightventricularoutflowtractafter
repairofcongenitalheartdiseasesuchastetralogyofFallot.Thecatheterdeliveredvalvesareusedbothtorelievestenosisand/orregurgitationin
previouslyplacedvalvesandconduitsaswellasinthenativepulmonaryroot.
Theobviousadvantageistoavoidacardiacreoperation.Resultshavebeen
excellentwithaproceduralsuccessrateofover95%andmortalityrateof1.5%.
Complicationsincludedconduitruptureof4.1%andcoronaryartery
compromiseof1.3%.156
ValveRepair
Asdiscussedintheprecedingsection,optionsforreplacementofvalvesare
limitedduringchildhood.Repair,iffeasible,preservesthepotentialforgrowth,
avoidsanticoagulation,andalsotheneedforvalvarre-replacement.The
disadvantagesofrepairincluderesiduallesions,suchasstenosisand
insufficiency,andlimiteddurability.Decision-makingregardingthesuitabilityof
alesionforrepairiscomplex,andmusttakeintoaccounttheprosandcons
outlinedabove,aswellasthespecificlesionandtheabilityofthesurgeon.
Repairofthemitralvalveiscommonlyperformedandusestechniquesthat
borrowedfromtheexperienceinadults,aswellastechniquesthathavebeen
developedfromrepairofatrioventricularseptaldefects.Repairofthemitral
valveisfrequentlysuccessfulanddurable.157,158Incontrast,replacementofthe
mitralvalvenecessitatesarepeatedreplacementinalmostthree-quartersof
patients.159Mitralvalvopathyamenabletosurgicalinterventionmaybethe
resultofrheumaticheartdisease,acquiredandcongenitalcardiomyopathies,
Marfandisease,Shone'scomplex,andcongenitalmitralstenosis.Techniquesfor
repairvarydependingontheetiologyofthepathology.160Forrepairofmitral
