Andersons pediatric cardiology 560
Bạn đang xem bản rút gọn của tài liệu. Xem và tải ngay bản đầy đủ của tài liệu tại đây (82.74 KB, 3 trang )
averageheartratebelow50beats/min,abruptpausesintheventricular
ratethataretwotothreetimesthebasicsinuscyclelength,orcases
associatedwithsymptomsduetochronotropicincompetence.
3.Sinusbradycardiawithcomplexcongenitalheartdiseaseandaresting
heartbelow40beats/minorventricularpausesexceeding3seconds.
4.Congenitalheartdiseaseandimpairedhemodynamicsasaresultofsinus
bradycardiaorlossAVsynchrony.
5.Unexplainedsyncopeinapatientwithpriorcongenitalheartsurgery
complicatedbytransientcompeteAVblockwithresidualfascicular
bockafteracarefulevaluationtoexcludeothercausesofsyncope.
ClassIIB(weightofevidence/opinionislesswellestablished):
1.Transientthird-degreeAVblockthatrevertsbacktosinusrhythmwith
residualbifascicularblock.
2.Congenitalthird-degreeAVblockinchildrenoradolescentswithan
acceptablerate,narrowQRScomplex,andnormalventricularfunction.
3.Asymptomaticsinusbradycardiaafterbiventricularrepairofcongenital
heartdiseasewitharestingheartratelessthan40Vorpausesinthe
ventricularrateexceeding3seconds.
ClassIII(thereisevidenceorgeneralagreementthatpacingisnot
useful/effectiveandinsomecasesmaybeharmful):
1.Transientthird-degreeAVblockwithreturnofnormalAVconductionin
anotherwiseasymptomaticpatient.
2.Asymptomaticbifascicularblockwithorwithoutfirst-degreeAVblock
intheabsenceofpriortransientthird-degreeAVblockaftersurgeryfor
congenitalheartdiseaseintheabsenceofpriortransientcompleteAV
block.
3.AsymptomatictypeIsecond-degreeAVblock.
4.Asymptomaticsinusbradycardiawiththelongestrelativeriskinterval
lessthan3secondsandminimumheartratemorethan40beats/min.
PacingforBradycardia-TachycardiaSyndrome
SinusbradycardiaalternatingwithAF/flutter,IART,orsinusnodereentry
tachycardiaisacommonproblemfollowingsurgeryforcongenitalheartdisease.
Mostofthesepostoperativetachycardiasarereentrantandthusuniquely
susceptibletooverdrivepacing.183Typicalanatomicsubstratesthatareproneto
tachy-bradyarrhythmiasincludethoseofpatientsfollowingatrialswitch
procedure,Fontan,andextensiveatrialsurgery.184Recentrecommendations
supportpermanentpacing(classIIA)forACHDandsinusorjunctional
bradycardiaforthepurposeofpreventingrecurrentIART.44Recent
recommendationsbythePediatricandCongenitalElectrophysiologySociety
furtherrecommenduseofadevicewithatrialantitachycardiacapability.44
Antiarrhythmicdrugtherapy—alongwithotherstrategiesthatincludecatheter
ablationorsurgicalrevisionwithcreationoflinesofblocktopreventintraatrial
reentrytachycardiacircuits—shouldalsobeconsideredwithinthe
armamentariumofmanagingcomplexadultcongenitalheartdisease.44
PacingforSyncopeandBreath-HoldingSpells
TheuseofDDDpacingforadultpatientswithrecurrentneurallymediated
syncopeandprolongedpausesmaybereasonable,especiallyinthosewith
minimalornoprodrome.40Forsuchpatients,pacingmayincreasethetimefrom
theonsetofsymptomsortothelossofconsciousness.However,theuseof
pacemakersinchildrenandadolescentsiscontroversial,sincethereisa
considerableplaceboeffect.Theuseofpacinginthissituationisextremelyrare
andcasereportshaveacknowledgedtheuseofpacinginthosewithextreme
pauses.Fortherarechildwithpallidbreath-holdingspells,cardiacpacingmay
beconsidered.38,40Patientsundergoingpacemakerimplantationinthissubcohort
tendtoeventuallyoutgrowtheproclivityforpermanentpacing;oftensomelevel
ofreassurancecanbeprovidedtotheparents.
PacingforLong-QTSyndrome
AsubsetofpatientswithLQTSfailtorespondtoβ-blockersorLCSD;asa
resulttheyhaveongoingsymptomsand/orperiodsofTdP.Antibradycardia
pacingwithamoderatelyhighbaselineheartrate(80to90beats/min)hasbeen
usedasanadjuncttoβ-blockersinLQTS.185Therationaleisthatanincreased
heartrateshortenstheQTtogetherwhilealsominimizingpause-relatedQT
prolongation.Althoughthesoleuseofantibradycardiapacinghasdiminished
somewhatwiththeadventoftheICDs,thereremainsaroleforpacing.Some
high-riskneonateswithaverylongQTintervalmayhavefunctional2:1block
andthusmaybenefitfrompacing.Thisgroupofpatientsisathighrisk,buta
multimodaltreatmentregimenofpacing,β-blockers,andLCSDmaybehelpful.
Recentdatasuggestthatthesehigh-riskpatientsmayhaveabetterthanexpected
outcomeifsuchastrategyisdeployed.133IsolatedsecondaryAVblockmaybe
seeninuteroandshouldraisesuspicionforaLQTS.128Provenpause-dependent
initiationofventriculararrhythmiaswithorwithoutLQTSisaclassIindication.
PacingmayalsobeofsomebenefitinpatientswithLQT3withsignificantsinus
bradycardia.TheincreasinguseofICDsinhigh-riskLQTSpatientsisofproven
benefitandislikelytobesaferthanpacingalone,despitethepotentialproblem
ofT-waveoversensinganddefibrillatorshockscausingadrenergicsurgesand
electricalstorm.Thequalityoflifeinchildren(8to18yearsofage)withcardiac
implantableelectronicdevicesasperceivedbythechildrenandtheirparentsis
similartothatofchildrenwithseverecongenitalheartdisease.Asalways,the
decisiontoimplantadevice,pacemakerordefibrillator,shouldbeindividualized
andboththeacuteandlong-termissueswiththedevicemustbecarefullyand
thoroughlydiscussedwiththepatientandhisorherfamily.
PacingforHypertrophicCardiomyopathy
Dual-chamberpacingcantheoreticallydiminishtheLVoutflowobstructionin
hypertrophiccardiomyopathybychangingtheactivationsequenceofthe
ventricularmyocardium.Inpatientswithhypertrophiccardiomyopathy,typically
theAVnodeconductionisintactandashort-programmedAVintervalisrequired
toaltertheactivationsequence.Theresponsetopacingisvariable,andalthough
thistechnologyseemsreasonabletoalterthephysiology,theresultshavelargely
notdemonstratedabenefit.
