Andersons pediatric cardiology 1660
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Signal-AveragedElectrocardiography
Signal-averagedECG(SAECG)isusedtoevaluateforevidenceoflate
potentials,whichconstituteaminorcriterionforARVC.Therearelimiteddata
regardingtheuseandpredictiveabilityofSAECGinchildren.Amongpediatric
patientswithknownmutations,noneshowedabnormalitiesintheirSAECG
priortoage10years,whereasapproximately20%showedabnormalitiesafter
age11.392ItisunclearifthepresenceofearlychangesintheSAECGidentify
patientsathigherriskfordevelopingclinicaldisease.
AmbulatoryElectrocardiography
Ambulatoryelectrocardiographyfrequentlyrevealsventricularectopyranging
fromisolatedectopicbeatstoventriculartachycardiaandfibrillation.The
arrhythmiaspresentarepredominantlymonomorphic.390,391NonsustainedVT
hasalsobeenshowntobeariskfactorforappropriateICDtherapyandthusmay
helpguideriskstratificationandICDimplantation.393
CardiopulmonaryExerciseTesting
Cardiopulmonaryexercisetestingmaybeusefulindetectingventricular
arrhythmiasinducedbyphysicalactivityduringtheinitialevaluationphaseand
priortothedevelopmentofothermanifestationsofdiseaseingenecarriers.394
Echocardiography
Echocardiographymayshowrightventriculardilation,aneurysm,regionalwall
motionabnormalities,areducedtricuspidannularplanesystolicexcursion,and
systolicdysfunction.395,396However,themajorityofthesefindingsarenot
presentinchildhood,wherearrhythmiaisthepredominantphenotypic
expressionofdisease.Advancedimagingparameterssuchasmechanical
dispersionandstrainarecurrentlybeingevaluatedonalargerscale.397
MagneticResonanceImaging
CMRIistakinganincreasinglyimportantroleinthediagnosisofARVC,given
itsabilitytoobtainaccurateandreproduciblemeasurementsofventricular
volumesandsystolicfunctioninadditiontotissuecharacterization.398Itis
importanttonotethatARVCdiagnosisisbasedontheconstellationoffindings.
CMRIabnormalitiesalone,especiallyintheabsenceofelectrophysiologic
findings,shouldraisethesuspicionforotherdiseaseprocesses.399
Management
Clinicalmanagementfocusesonreducingtheriskofdiseaseprogressionthrough
appropriateactivitymanagement,symptomatictreatment,andarrhythmia
monitoringandtherapy.β-blockertherapyisrecommendedinpatientswith
recurrentVT,appropriateICDtherapies,orinappropriatetherapiesduetoatrial
tachyarrhythmias.400TherapymayalsobeconsideredinallpatientswithARVC,
giventheroleofadrenergicstimulationinarrhythmias.Amiodaronemaybe
consideredfortheacutemanagementofsymptomaticarrhythmia;however,it
doesnotappeartoprovideadequateprotectiontoobviatetheneedforICDin
manypatients.401Patientswhodevelopsystolicdysfunctionorheartfailure
shouldbetreatedwithstandardpharmacologictherapy.Prophylacticuseofheart
failureorantiarrhythmicmedicationsisnotrecommendedforgenecarriers
withoutphenotypicdisease.
Implantabledefibrillatortherapyisaneffectivetreatmentforpotentiallylifethreateningarrhythmias.393However,thebenefitmustbeweighedagainstthe
riskofcomplications,whichappeartobehigherinARVC.402,403Anumberof
riskfactorsforarrhythmiceventshavebeenidentifiedandhavebeenusedto
constructaninitialflowcharttohelpguideICDimplantation.400
LeftVentricularNoncompaction
Cardiomyopathy
Definition
IsolatedLVNCisastructuralabnormalityoftheleftventriclecharacterizedbya
two-layeredmyocardiumthatconsistsofdistinctcompactedandnoncompacted
segments,prominentventriculartrabeculations,andintertrabecularrecesses.404
ThediseasewasfirstdescribedbyGrantin1926andisaclinically
heterogeneousdisorder.Thetwo-layeredmyocardiumistypicallyseenatthe
apexandlateralwalloftheleftventricledistaltothepapillarymusclesbutmay
beseeninanyoftheLVsegments.Thereiscontinuitybetweenthecavityofthe
leftventricleandthetrabecularrecesseswithoutanydirectconnectiontothe
epicardialcoronaryarteries.Thelayersconsistofaspongyendocardiallayerand
athinner,compactedepicardiallayer.Thediseasehasbeenknownbyavariety
ofnames,includingfetalmyocardiumandspongymyocardium.LVNCis
classifiedasadistinctcardiomyopathybytheAHA.3However,itremains
unclassifiedbytheESC,asthereremainsdebateastowhetherLVNCrepresents
aprimarycardiomyopathyversusatraitsharedbyothercardiomyopathy
phenotypes.4ThetermisolatedLVNCistypicallyusedforLVNCwithout
evidenceofcongenitalheartdisease.
Epidemiology
LVNChasbeenconsideredtobeararediseasebutisincreasinglydiagnosedin
clinicalpractice.Thetrueincidenceandprevalenceofthediseaseremain
difficulttoestimategiventhelackofconsensusondiagnosticcriteria.Giventhis
information,thereportednumbersininfants,children,andadultsarelikely
underestimates.TheincidenceofLVNCininfantsandchildrenhasbeen
reportedas0.8and0.12per100,000peryear,respectively.270Theprevalencein
adultshasbeenreportedat1per5000inthegeneralpopulation,althoughthe
estimatesvarywidelybasedonthesetting(hospitalvs.communityvs.tertiary
care).LVNCisalsorelativelycommoninthesettingofheartfailure,occurring
in3%to4%ofheartfailurepatients.Inadultsreferredforechocardiography,the
reportedprevalencerangedfrom0.01%to0.03%.405Thisisverylikelya
