Andersons pediatric cardiology 1758

TotalArtificialHeart
Thetotalartificialheart(TAH;SynCardia)isanimplantablebiventricular,
pneumaticcompressiondevicethatreplacesbothventriclesanatomicallyand
mechanically(Video66.1).Itisavailablewitha70-mLchamber,whichisFDA
approvedforuseinpatientswithaBSAgreaterthan1.7m2.TheTAHwas
introducedin1982byRobertJarvikastheJarvik-7.Ithassincebeenknownas
theSymbion,CardioWest,andiscurrentlytheSynCardiaTAH.In1985the
Jarvik-7bridgedapatient9daystotransplant,andanIDEforbridgeto
transplantwasinitiated.By1993,CardioWestownedtheJarvik-7,andanIDE
studywasunderwayforitsuseasbridgetotransplantationordestination
therapy.In2001,SynCardiatookovertheJarvik-7,andin2004,theFDA
approvedtheSynCardiaTAHforbridgetotransplantation.Unfortunately,only
30drivers,knownas“BigBlue”(190kg),existedworldwide,whichlimiteduse
oftheTAHuntil2009,whenthemuchsmallerCompanionDriverwas
introducedandquicklyfollowedbytheportableFreedomDriver(weighing
approximately6kg)in2010.SincetheintroductionoftheFreedomDriver,
whichcanbecarriedinabackpack,TAHusehastripled,andmorethan40%of
themorethan1750implantshavebeenperformedinthepast6yearscompared
withtheprevious25years.
Inpediatrics,theTAHisnotmeanttoreplaceexistingdevicesinthecareof
childrenbuthelpcareforthosechildrenwhodonothaveagreatmechanical
supportoption.First,byremovingbothventriclesandatrioventricularvalves,
thereisnorightheartfailure,atrioventricularvalveregurgitation,cardiac
arrhythmias,ventricularclots,intraventricularcommunications,orlowblood
flow.This,combinedwithahighCO,makesitidealforpatientswithchronic
rejectionpostorthotopichearttransplant(whereimmunosuppressioncanbe
stopped),alatefailingFontancirculationwithend-organdysfunction,chronic
rightheartfailurewithLVAD,significantbiventricularrestrictivedisease,alarge
ventricularclotburden,primaryarrhythmia-inducedheartfailure,cancer,or
multipledefectsthatmayrequirerepairpriortoVADplacement.37Thereisvery
littleknownaboutlong-termoutcomesinpediatricsfortheTAH,butarecent

compilationoftheworldexperienceofpatientsaged21yearsoryounger
reported43devicesimplantedfrom2005to2015.38Positiveoutcomeswere
reportedin63%ofthepatientsat90days,whichissimilartotheadultTAH
experience.
BecauseofimprovingresultsandtheincreaseduseoftheTAHinpediatrics


andcongenitalheartpatients,theSynCardia50/50-ccTAHwasdeveloped.Itis
currentlythesubjectofaclinicaltrialforBSAsrangingfrom1.2to1.85m2or
thosewhocanbedemonstratedtofitbyvirtualimplantationtechnique,which
representsthefirsttimethatvirtualfithasbeenacceptedasacriterionbythe
FDA.StudiessuchasthosebyMooreetal.39havedemonstratedthatvirtualfit
changedtheeligibilityof33%ofpatientsandallowedfitdowntoaBSAof0.9
m2.Thishasgreatlyexpandeditsuseinpediatricpatients.TheongoingIDEtrial
ofthisdevicepresentlyhaseightpatientsintheprimaryandsecondaryarms,
withasurvivalofgreaterthan80%.However,theworldwideexperienceof60
patientshasdemonstratedthatthe50/50-mLdevicehashaditsdesiredeffect,
althoughnumbersremainsmall,ofallowingTAHsupporttoincreasein
congenitalpatients(4%to9%),pediatrics(4%to13%),andperhapsmost
significantlyinwomen(12%to70%).

ContinuousFlowVentricularAssistDevices
TheintroductionofCFdevicestothepediatricfieldledtoseveralimportant
changesindevicedesign,notleastofwhichwassmallerdevicesizes,allowing
forintracorporealsupportinpediatrics.TheCFdevicesalsocamewithalower
morbidityprofileandlesspumpthrombosis.Theseadvantages,coupledwiththe
abilitytogohome,ledtosupportingpatientsonthesedevicesregardlessof
whetherornottheywerelistedfortransplantation.WithaCFdeviceinplace,
patientscanbedischarged,resumemost“normal”lifeactivities,andbe
evaluatedatalaterdateforpotentialhearttransplant.However,only

approximately50%ofCFVADpediatricpatientsaredischargedhome.

HeartmateII
ThoratecHeartMateIIhasarotary,axialflowpumpthatcanprovideCFat2.5
to10L/min.Duetoitssize,theHeartMateIIisapprovedforbridgetotransplant
orasdestinationtherapyinpediatricpatientswithaBSAof1.4m2orgreater
andcanbeusedfordischargehome.Thisdevicehasbeentriedandimprovedin
adultpatients,withmorethan25,000implantsworldwide.Ofthose,6451
deviceshavebeeninplacegreaterthan3years,2513devicesmorethan5years,
and46formorethan10years.Thisdevicehasalowincidenceof
thromboemboliceventsandexcellentoutcomesinpediatrics,withgreaterthan
95%ofpatientseithertransplanted,recovered,orremainingonthedeviceat6


monthsafterimplantinareviewofINTERMACSdata.40Themostfrequent
complicationwasbleeding(21%),andstrokeandsepsisoccurredin7%and
11%,respectively.Eveninthisearlyseries(2008–2011)withonly28patients
followedover6months,theresultsofthisstudyareveryencouragingforthis
device.Asof2017,AbbotthasacquiredThoratecandwithit,theHeartMate3,
whichwasFDAapprovedfor“short-termhemodynamicsupport(e.g.,bridgeto
transplantorbridgetomyocardialrecovery)”inlate2017,althoughithasbeen
availableforshort-andlong-termuseinEuropesince2015.41TheHeartMate3
usescompletemagneticlevitationtechnologytoprovidefrictionlessrotor
movement,reducinghemolysisandthrombosis.AswithformerCFdevices,we
anticipatetheHeartMate3willbegintoseeuseinselectpediatricpatients
(Video66.2).

HVAD
HeartWareHVAD(Medtronic)isanintracorporealcentrifugalLVADthathas
allowedfordischargetohomeinchildrendowntoaBSAof1.0m2.Thisdevice

isintracorporealandissmallerthantheHeartMateII,improvingdevicecomfort
andmakingitusefulinpatientswithpoorhealing,suchasDuchenemuscular
dystrophy.18Anearlymulticenterstudyfrom2015reportedexcellentoutcomes
in12patientsfromaroundtheworldwhoweredischargedhomewithamean
supporttimeof290days,whilecommentingonat-homemanagement.42Patients
rangedfrom8to15yearsofage,andthesmallestwasan18-kgchildwitha
BSAof0.8m2,althoughimplantationdowntoaBSAof0.6m2hasbeen
reported.43Eightofthechildrenreturnedtoschool.Thirtyreadmissions
occurredin10patients(0.02events/personpermonth)mostcommonlyfor
drivelineinfection(22%).Nopumpthrombosisorneurologicthrombotic
episodesoccurred.Attheconclusionofthestudy,fiveofthepatientshadbeen
bridgedtotransplantation,fivewereawaitingtransplant,onedevicewas
explantedafterrecovery,andthefinalfamilyelectedtoremainonthedeviceas
destinationtherapy.
InananalysisoftheglobalexperiencewiththeHeartWareHVAD,Conwayet
al.reportedon205pediatricpatientsin2017.43aMalesweremorefrequently
implanted(61%),andcardiomyopathywasthemostcommondiagnosis(82%).
Morethan50%ofpatientsweredischargedhome,andthisnumberimproved
withexperience.At1year,65%hadbeentransplanted,21%remainedonthe