Andersons pediatric cardiology 1932

FIG.73.33 ChangeinleanmassandpeakVO2withresistancetraining
versusnontrainingcontrols.Errorbarsshownarestandarderrorofthe
mean.VO2oxygenuptake.(FromCordinaR,O'MeagherS,KarmaliA,et
al.Resistancetrainingimprovescardiacoutput,exercisecapacityand
tolerancetopositiveairwaypressureinFontanphysiology.IntJCardiol.
2013;168[2]:780–788.)

DoexerciseprogramshavethecapacitytoimproveQOLandlongevityofthe
Fontancirculation?Lowerfunctionclassandlowerexercisecapacityareknown
tobepredictorswithFontanfailure.Thehypothesisthatimprovingexercise
capacitythroughtrainingwillreducetheriskoffailureisattractivebuthasyetto
beprovenandwilllikelybethefocusofmuchattentionoverthecomingyears.


OtherMedicalTherapies
Althoughwidelyused,thereislittleevidencetosupportroutinetreatmentwith
ACEinhibition,β-blockade,oraldosteroneinhibitors.412Indeed—asdetailed
earlier—randomizedstudieshavedemonstratednobenefit,andlong-term
studiesofsafetyhavenotbeenreported.249Likewise,modificationofthe
prothromboticstateandreductionoftheriskofthrombosiswithantiplateletor
anticoagulantmedicationremainunproven.392Giventheheterogeneousnature
ofmorphologicandfunctionalabnormalitiesinthosewithaFontancirculation,
andthelongtime-courseoverwhichfailureoftheFontancirculationoccurs,itis
doubtfulthatnewtrialswillshedlightontheefficacyofthesemedicationsinthe
foreseeablefuture.Nevertheless,theremaybesubsetsofpatientswhowill
benefitfromcertaintreatments.Forexample,one-halfofadultFontanpatients
haveaspirinresistanceandmaybenefitfromotherformsofantithrombotic
prophylaxis.393Furthermore,variableexpressionofgeneticpolymorphismsin
theRAAsystemandkallikrein-bradykininpathwaysinfluencestheoutcomein
adultswithcoronaryarterydiseasetreatedwithACEinhibitors.413Further
investigationintheFontanpopulationmaywellidentifysubsetsofpatientsmore

likelytobenefitfromthistypeoftreatment.

PracticeVariation,Networks,andRegistries
Becausethereislittleinformationtosupportacommonlifetimesurveillance
planforpatientswithaFontancirculation,thereissignificantpracticevariation
between,andoftenwithin,institutions.248,249Therecentemergenceofregional
andmultiinstitutionalregistriesandnetworksprovidesthebasisfortheuniform
surveillanceandauditofrelativelylargegroupsofpatients.35,414Iterative
assessmentofsurveillanceprotocols,withattentiontothedetectionofearly
signsoffailure,hasthecapacitytoimproveoutcomeandprovidean
increasinglyrationalandcost-effectivelifetimecarepathway.415

SurgicalDesignandComputationalFluid
Dynamics
ThefunctionalstatusofpatientslateafterFontanisintimatelyassociatedwith
theoptimizationofflowoftheFontancircuit.Thereisconvergingevidencethat
thesmallerthelossofkineticenergytothebloodflowisintheFontancircuit,


thebettertheexercisecapacity.Onecouldexpectthattheoperationswiththe
bestdesignmayalsoresultinthebestlong-termoutcomes.Yetthispopulationis
characterizedbyawidevariationofpulmonaryarterysize,position,and
orientationsothatoneoperationthatfitsallisnotpossible.Progressinthis
directionistwofold.First,itislikelythatimprovingminordistortionand
obstructionintheFontanpathwaybyinterventionalcatheterizationorwith
reoperationcouldbenefitsomepatients.Secondly,computationalflowdynamic
technologyhasthecapacitytoassistpatient-specificdesign,sothatmodelscan
beconstructedbeforetheFontanoperationandtheFontancircuitcanbetailored
foranindividualpatientinawaythatoptimizesflowandminimizesenergyloss.
Therehasbeensignificantprogressinthisarea.Indeedtherationaleforthetotal

cavopulmonaryconnectionversionoftheFontanoperationwasdesignedusing
earlycomputationalfluiddynamicstechniqueswiththeprincipleofoptimizing
circuitflowenergeticsandminimizingenergylostthroughcollisionand
recirculation.4Nevertheless,despitepromisingresults,progressintheareaof
individualizingFontandesignhasnotyetbeentranslatedintowidespreaduse.

ImplantedVentricularAssistDevices
ThepopulationofpatientswithaFontancirculationisexpectedtodoubleinthe
next2decades,anditislikelythattherewillnotbeenoughdonororgansforthe
growingnumberofthosewithafailingFontancirculation.32,416Hencethere
wouldbetremendousbenefitifamechanicaldevicewereabletoprovidesafe
long-termcirculatorysupportasanalternativetotransplantation.Todate,
attemptstosupporttheFontancirculationwithconventionalassistdevices
designedforthefailureofthesystemicleftventriclehavebeen
disappointing.417,418Thesedevicesinvolvetheimplantationofapneumatic
paracorporealdevicebetweenthesystemicventricleandtheaorta.
Unfortunately,thismodeofsupportisnotabletoadequatelydecreasethe
systemicvenouspressureinthefailingFontancirculation,andtheuseofthese
typesofdevicesisassociatedwithmortalityofgreaterthan40%.Itislikelythat
patientssurvivingthismodeofsupportarethosewhosemainmodeoffailureis
primaryventriculardysfunction.417–420Twoalternativestrategieshavebeen
initiated.Somehavesuspectedthatmechanicalsupportofthefailingsystemic
ventriclewithacontinuousflowdevicemaybepreferable,andthefirst
successesofthisstrategyarecurrentlyemerging.421Itispossiblethatcontinuous
flowdevicesaremoreaptatmaintainingalowpressureinthepulmonary