Andersons pediatric cardiology 1653
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ThepotentiallylifesavingimpactofICDsisnotwithoutdevice-associated
morbidity.FortypercentofchildrenmayexperienceanICD-related
complication(29%inappropriateshock).231Themajorityofpatientswho
receivedaninappropriateshockhadeithersinustachycardia(48%)or
supraventriculartachycardia(19%).Althoughtherewasnodifferenceinthe
frequencyofinappropriateshockamongpatientsonmedicationatthetimeof
ICDimplantation,itisunclearwhethermoreaggressivemedicaltherapymay
mitigatethisrisk.TherearepromisingearlydatausingsubcutaneousICDsin
adultswithHCM,butfurtherstudyisneededbeforethisapproachcanbe
recommended.263
Disease-ModifyingTherapy
GreaterunderstandingofthemolecularpathwaysunderlyingHCMhasledto
greaterinterestinthepotentialofdisease-modifyingtherapy.Thusfar,trials
exploringtheuseofmedicaltherapyhavebeennegative.97,264Recruitmentis
ongoingfortheVANISH99andLIBERTY-HCM98trialinvestigatingtheroleof
valsartanandeleclazineinmedicaltherapyforHCM.
ExerciserestrictionsinHCMarelargelybasedonexpertguidelines;it
remainsunclearifthereisanappropriatelevelofactivitythatmayhelpto
maintainlong-termcardiovascularhealthwhileminimizingtheriskofcardiac
events.Preliminaryevidencesuggestsmoderate-intensitymonitoredexercise
maybesafeandassociatedwithimprovementinexercisecapacity265;however,
thistopicrequiresfarmorescrutinyandevaluationbeforethecurrentexercise
recommendationscanbemodified.
DilatedCardiomyopathy
Definition
DCMisdefinedasleftventriculardilationandsystolicdysfunctioninthe
absenceofcoronaryarterydisease,pericardialdisease,orabnormalloading
conditionssufficienttocausefunctionalimpairment.2DCMmaybeprimaryor
secondary;however,thephenotypeisacommonfinalresponsetogeneticor
environmentalinjury.
Epidemiology
TheoverallannualincidenceofDCMinchildrenis0.6to0.7casesper100,000
populationperyear,althoughthereisanage-dependentrisk,withthehighest
incidenceinpatientslessthan1yearofage.266–270Thereisalsoage-dependent
penetrance,withamuchhigherprevalenceofDCMandasymptomatic
dysfunctioninthecommunity.271Thereisnogenderpredominance;however,
thereisobviouslyanincreasedfrequencyofmalesaffectedamongpatientswith
X-linkeddisease(e.g.,neuromusculardisease).266–269,272
ClinicalOutcomes
Althoughtheoverall1-and5-yearfreedomfromdeathortransplantisabout
70%and60%,respectively,theclinicaloutcomesvarybycause(Fig.
61.7).266,270,272,273Overallsurvivalhasimprovedwithtime;however,the
majorityofthesurvivalbenefitissecondarytotheincreasedutilizationofheart
transplantation.274,275Olderage(>5to6yearsofage),worsesystolicfunction,
andgreaterleftventriculardilationareriskfactorsforadverseoutcomes
(compositeoutcomeofdeathortransplantation).272,276Approximatelyone-third
ofpatientswillexperiencenormalizationoffunction,withhigherratesof
recoveryamongyoungerpatientsandpatientswithbetterinitialsystolic
function.273,277,278Theratesofrecoveryinpatientswithmyocarditishavebeen
alternatelydescribedashigherandlowerthanthoseofpatientswithidiopathic
orfamilialDCM.273,277,278Thereappeartobenodifferencesinoutcomeamong
patientswithidiopathicandthosewithfamilialDCM.276
FIG.61.7 Freedomfromdeathortransplantationinchildrenwithdilated
cardiomyopathyaccordingtounderlyingcause.DCM,Dilated
cardiomyopathy.
Etiology
DCMisassociatedwithanumberofgeneticcauses(seeTable61.1).
Approximately30%to50%ofallpatientswithDCMhavefamilialdisease.279
DatafromthePediatricCardiomyopathyRegistryandNationalAustralian
ChildhoodCardiomyopathyStudyclassifyapproximately10%to15%of
patientsashavingfamilialdisease,whereasindividualcentersdescribeaslightly
higheryield(approximately25%).267,276,280,281Studiesexaminingthefrequency
ofapositivegenetictestrangefrom15%to50%.281–283Thediscrepancyinthe
resultsislikelyduetodifferencesinthepopulation(especiallyage)aswellas
variablecriteriausedtoassesspathogenicity.Estimatesregardingtheyieldare
alsocomplicatedbytheevolvingassessmentofmutationpathogenicity.The
yieldofgenetictestingmaybeincreasedbyasmuchas70%throughtheuseof
multidisciplinaryclinics,includingcardiologyandgenetics.280
