Andersons pediatric cardiology 1659
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ArrhythmogenicRightVentricular
Cardiomyopathy
Definition
Arrhythmogenicrightventricularcardiomyopathyischaracterizedbyfibrofatty
replacementofcardiomyocyteswithassociatedcardiacdysfunctionand
ventriculararrhythmias.Inspiteofitsname,fibrofattyreplacementmayoccurin
eithertherightorleftventricle(~50%ofadultcaseshaveleft-sided
involvement)andleft-dominantformsaredescribed.368Fattyreplacementofthe
ventricleistypicallyfollowedbyventriculardysfunction,dilation,and
arrhythmia.
Epidemiology
TheprevalenceofARVChasbeenestimatedtorangefrom1:1000to1:5000,
butascertainingthetrueprevalencehasbeenlimitedbychangingdiagnostic
criteria,age-andgender-dependentpenetrance,aswellastertiaryreferral
bias.369–371Thediseaseaffectsmenmorefrequentlythanwomen.Thediagnosis
isararecauseofcardiomyopathyinchildren,althoughitisanimportantcause
ofsuddendeathinteenageandyoungadultathletes.372,373
ClinicalOutcomes
Arrhythmogenicrightventricularcardiomyopathyhasanage-andactivitydependentphenotype.374,375Fibrofattyreplacementofthemyocardiumtypically
beginsintheepicardialormidmyocardialtissue.Patientsaretypically
asymptomaticintheinitialphase,althoughtheyareatriskofsuddendeath.
Symptomsandclinicallysignificanteventsveryrarelyappearbeforeage13.376
Thesecondphaseofdiseaseischaracterizedbyanelevatedriskoflifethreateningarrhythmias.Thehighestriskforlife-threateningarrhythmiasoccurs
betweenages20and40,althoughsuddendeathmayoccurintheteenageyears
aswell.377Approximately10%ofpatientswillhavesuddendeathoraborted
suddendeath(~5%ofpatientseach)astheirfirstmanifestationofdisease.376–378
Thelatestageofdisease(inadulthood)ischaracterizedbycontinuedriskfor
arrhythmiasaswellastheonsetofventriculardysfunction(right,left,orboth
dependingonthephenotype).376,378Inspiteoftherisks,theoverallmortality
rateisbelow1%amongnontertiaryreferralcenterpopulations.379
Etiology
Thirtyto50%ofpatientswithARVCwillhaveafamilyhistoryofdiseaseand
approximately40%to50%ofpatientswillhaveadisease-causingmutation
identified,althoughnotallpatientswithamutationwilldevelopphenotypic
disease.371,376Thediseaseistypicallyinheritedinautosomaldominantfashion,
andanumberofdesmosomalproteinshavebeenassociatedwithit(seeTable
61.1).Desmosomalproteinsandothercomponentsofintercalateddiskshave
beenimplicatedindiseasedevelopment.Theseproteinsmodulatecell-cell
adhesionandelectromechanicalcoupling,andtheirrolesineachhasbeenused
toexplaintherelationshipbetweendiseaseseverityandexercise.374,375,377Afew
extradesmosomalgeneshavealsobeenimplicatedinARVC(e.g.,ryanodine
receptor).380Asintheothercardiomyopathies,widespreadexomedataare
modifyingourunderstandingofthepathogenicityofmutations.381
Pathology
Thepathologicfindingsofdiseasevarybasedonpatientageandstageof
disease.Earlyautopsy-andcatheterization-basedstudieshaveidentified
pathologyprimarilyintheapical,inflow,andinfundibularsegmentsoftheright
ventricle,subsequentlycalledthe“triangleofdysplasia.”382Morerecently,
widespreadpatientscreeningandtheuseofCMRIdatahavesuggestedthat
apicalinvolvementmayinfactbealatemanifestationofdisease.383Left
ventriculardiseaseiscommoninthelatestagesofdiseasebutmaybethe
predominantmanifestationofdiseaseinaminorityofpatients.384
ClinicalFeatures
ThediagnosticcriteriaforARVCwererevisedin2010andrelyon
multimodalitydiagnosticevaluationinadditiontofamilyhistory.385Basedon
thecurrenttaskforcecriteria,patientsarecategorizedas“definite,borderlineor
possible”ARVC.
Symptoms
Themajorityofpatientsareasymptomaticthroughtheirearlyteens.Symptoms
typicallybeginintheseconddecadeoflife,atwhichpointthereisincreasing
riskofcardiovasculareventsduetosuddendeathandeventuallyheart
failure.369–371,376,377Arrhythmicsymptomspredominateinchildren(e.g.,
palpitations,syncope),astheriskofheartfailureislowuntiladulthood.Therisk
ofcardiovasculareventsappearstobelifelong,evenforpatientswhopresent
latewithdisease.386
PhysicalExamination
Thephysicalexamfindingsaregenerallyrelativelyunremarkableduring
childhood.Theapicalimpulseistypicallyunremarkableuntiltheonsetof
ventriculardilationanddysfunction.Theremaybeamurmurofatrioventricular
valveregurgitationifdilationanddysfunctionarepresent.AprominentlysplitS2
maybepresentinthesettingofrightbundlebranchblock.Dermatologic
manifestationsofdiseasemaybepresentinpatientswithcardiocutaneous
disease(NaxosdiseaseandCarvajalsyndrome).
Electrocardiography
TheECGtypicallyshowsinvertedTwaves(intheabsenceorrightbundle
branchblock)andmayshowpresenceofanepsilonwaveintheanterior
precordialleads(V1toV3).However,T-waveinversioninleadsV1andV2isa
normalfindingin3%to5%oflateteensandearlyadults,soitcanposea
diagnosticconundrum,especiallyinyoungathletes.387–389T-waveinversion
beyondV2islesscommoninthispopulationandshouldraisegreatersuspicion
forARVC.T-waveinversionintheinferiororlateralleadsissuggestiveofleft
ventriculardisease.VentricularectopymaybepresentonarestingECG.For
patientswithclassic,right-dominantdisease,aleftbundlebranchblockpattern
istypical,giventhattherightventricleistheoriginofectopy.Theaxismaybe
superiororinferiordependingontheexactlocationoftheectopicfocus.390,391
Patientswithleft-sidedorbiventriculardiseasemayshowalternate
morphologies.
