Andersons pediatric cardiology 1456

BackgroundandEpidemiology
ARF,adelayedautoimmunereactiontogroupAstreptococcalinfection,isnow
rarelyseeninhigh-incomecountries,whereRHDispredominantlyreportedin
theagingpopulationasaconsequenceofARFseveraldecadesearlier,usually
occurringduringchildhood.1However,intheworld'spoorestpopulations,RHD
remainsaleadingnoncommunicablediseaseoftheyoung.2In2010,an
estimated34.2millionpeopleworldwidehadRHD,resultingin345,110deaths
and10.1milliondisability-adjustedlife-yearslostperannum.2TheseGlobal
BurdenofDiseasefigurescouldbeanunderestimateduetolimitedglobaldata,
underdiagnosis,andscarceformalreportingsystems.2,3
Regionalheterogeneityexistsregardingageofonset,modeofpresentation,
andspecificvalvarabnormality,whichareinfluencedprimarilybythe
socioeconomicandmedicalbackgroundsofthepopulationsinvolved.4,5Global
burdenofdiseaseisdepictedinFig.55.1.4Childrenagedbetween5and15
yearsareatgreatestriskofaprimaryepisodeofARF.Inendemicpopulations,
thepeakprevalenceofRHDisbetweenages25and45years,reflectingthe
cumulativeeffectofrecurrentepisodesofARF(Fig.55.2).6

FIG.55.1 Globalprevalenceofrheumaticheartdiseasefrom1990to
2013.


FIG.55.2 Ageandgenderdistributionof3339childrenandadultswith
rheumaticheartdisease(RHD)intheinternationalREMEDYregistryof
RHD.


PathogenesisofChronicRheumatic
HeartDisease
TheexactpathogenesisofARFisincompletelyunderstood.RHDisthoughtto
betheresultofimmune-mediatedendothelialandconnectivetissuedamage.7

Cardiacvalvesareespeciallypronetodamagebecauseoftheirthinstructure,
withasmallcoreofconnectivetissuecoveredbytwoendotheliallayers.7The
healingprocessofrheumaticvalvulitisleadstovaryingdegreesof
neovascularizationandfibrosis.Thisprocessdisturbsthedelicatearchitectureof
thevalvarapparatus,leadingtovalvarregurgitation,stenosis,orboth.Clinical
andechocardiographicregressionandevenresolutionofmildtomoderate
diseaseiswelldocumented.8–10However,ifthefirstepisodeofcarditisresultsin
moreseverevalvardysfunctionorifthevalvesareexposedtorecurrentepisodes
ofrheumaticfever,chronicdeformingvalvardamageanddysfunction
develops.11
Thepericardialeffusionseenduringtheacutephaseofrheumaticfever
usuallyresolveswithnolong-termsequelae.Myocardialimpairmentoccursonly
inthesettingofseverevalvardysfunction,andrecoverycanbeexpectedif
timelysurgicalcorrectionofthevalvardysfunctiontakesplace.12–14
ThehallmarkofRHDismitralvalve(MV)disease:mitralregurgitation(MR),
mixedMVdisease,and/orpuremitralstenosis(MS).Althoughpostmortem
studiesshowuniversalMVinvolvement,echocardiographicstudiesrevealthat
isolatedaorticvalve(AV)diseaseoccursinapproximately2%to8%ofpatients
withRHD(Fig.55.3).15,16Inadvanceddisease,thetricuspidvalveand,very
rarely,thepulmonaryvalvemayalsobeaffected,butseldomifeverwithoutMV
involvement.17