Andersons pediatric cardiology 568
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ArrhythmiasFollowingCongenitalHeart
DiseaseSurgery
Arrhythmiasoccurringafteropen-heartsurgeryforcongenitalheartdisease
contributegreatlytothemorbidityandmortalityofsurgery.Arrhythmiasthat
mightbetoleratedinthenormalheartresultinhemodynamicinstabilitywhen
theyoccurwithinthefirstseveraldaysaftersurgery.AlackofAVsynchrony
andrapidheartratesthatpreventdiastolicfillingresultinlowcardiacoutputand
mandateearlyrecognitionandtherapy.
JETisthemostfrequenthemodynamicallysignificanttachycardiaoccurring
postoperatively(Fig.22.40).ThisnarrowQRStachycardiacanhaveAV
dissociationwithasloweratrialthanventricularrate,although1:1retrograde
conductioncanoccur.Hemodynamiccompromiseoccurs,likelyasaresultof
thelackofatrialcontributiontocardiacoutput.RiskfactorsassociatedwithJET
aftercongenitalheartsurgeryincludeyoungerage,longercardiopulmonary
bypasstimes,andlongercross-clamptimes.86,88,205
FIG.22.40 Postoperativemanagementalgorithmforhigh-grade
atrioventricular(AV)block.EPS,Electrophysiologicstudy;LAD,leftanterior
descendingcoronaryartery;PVARP,postventricularatrialrefractoryperiod;
RBBB,right-bundle-branchblock.
Althoughtheprecisemechanismsarenotknown,thesettingofthearrhythmia
givescluestoitsetiology.Severalsurgicalandnonsurgicalriskfactorshave
emerged.Thesurgicalriskfactorsincluderesectionofmusclebundles,
correctionofRVOTobstruction,andcorrectionofVSDs.206,207Thereported
incidenceofJETvariesdependingonpatientselectionandstudylocation.Ina
nationwidestudyinFinland,theincidenceofJETinthecongenitalcardiac
surgerypopulationwas5%.88Thisstudyidentifiedmanyofthepreviously
reportedriskfactorsshowingthattheJETpopulationisoverallsickeras
comparedwiththeirage-andprocedure-matchedcontrols.However,inthe
logisticregressionmodel,onlylongercardiopulmonarybypasstimeandhigher
postoperativetroponinTwereidentifiedasindependentriskfactors,probablya
resultofmoredifficultsurgicalcorrectionandlargersurgicaltrauma.Further,
higherbodytemperatureattheonsetofarrhythmiawasfoundtobenearly
significant(P=.050).
TreatingJETinthiscriticallyillpopulationremainsachallenge.Therapy
shouldstartwithgeneralmeasuressuchascorrectingfever,anemia,
hypovolemia,andelectrolyteabnormalities,andoptimizingsedation.86,208
Someinstitutionsuseintravenousamiodaroneasaprimarytreatmentbecause
ofthegoodresponseinpatientswhofailedtorespondtoconventionaltherapies
orarehemodynamicallyunstable.88
TherearerecentreportsontheroleofdexmedetomidineforcontrolofJET.A
prospectiverandomizeddouble-blindcontrolstudyfollowed230consecutive
patientswhounderwentcorrectionsurgeryfortetralogyofFallot.209Onegroup
receivedaninitialbolusofdexmedetomidine(0.5µg/kg)over10minutes
followedbyacontinuousinfusionof0.5µg/kgperhour.Theinfusioncontinued
throughouttheoperationanduntilthechildwasweanedfromventilator.Inthe
controlgroupasimilarvolumeofnormalsalinewasgiven.JEToccurredmore
ofteninthegroupnottreatedwithdexmedetomidine.IfJEToccurredinthe
dexmedetomidine-treatedgroup,itwaslaterinonsetandofshorterduration.
Thetimetoextubationwasalsoshorterinthedexmedetomidine-treatedgroup.
Coolinghaslongbeenconsideredasageneralmeasureinthetreatmentof
JET.In1997Walshetal.foundthatofthemultipletreatmentstagesthey
employed,onlycorrectionoffeverandcombinedprocainamideandhypothermia
appearedtobeefficacious.208Othershaveadvocatedtheuseofsupplemental
magnesiumsulfateduringtherewarmingphaseofcardiopulmonarybypass,210
andnormalizationoftheserummagnesiumisanimportantgeneralmeasure.
Theadditionofintravenousamiodaronetothepharmacologicarmamentarium
hasimprovedthelandscapeinthisproblematicarrhythmia.Amiodaroneisa
classIIIantiarrhythmicdrugthatprolongsrepolarizationandrefractoryperiodof
atrial,nodal,andventriculartissues,witheffectssimilartothoseofbothβblockersandpotassiumchannelblockers.ItsactioninJETmaybeduetoits
