Andersons pediatric cardiology 571
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IntravenousamiodaroneandprocainamidearebothusedastherapiesforSVTin
theoperativeandnonoperativesetting.InacohortofchildrenwithSVT,
procainamideachievedgreatersuccessthanamiodaroneinthemanagementof
recurrentSVTwithoutstatisticallysignificantdifferencesinadverseevent
frequency.223
Intravenousamiodaronecanbeasuccessfultreatmentstrategy,but
hypotensionandAVconductiondisturbancecanoccurandhemodynamic
collapsehasbeendescribedwithitsuseespeciallyintheveryyoungpatients.224
Dexmedetomidinewasusedasaprimaryagentorasarescueifother
antiarrhythmicagentshadbeenusedinasmallstudyofarrhythmiasafter
congenitalheartdiseasesurgerythatincludedchildrenwithatrialarrhythmias.96
Thesewereyoungchildrenwithameanageof2months.Tenpatients(71%)
receivedaninitialloadingdoseof1.1±0.5µg/kgandacontinuousinfusionwas
administeredin12patients.Adverseeffectswereseenin4patients(28%);3had
hypotensionthatrespondedtofluidadministrationand1hadapossiblebrief
completeAVblock.Ofthe14patients,9weretransientlypaced.Theprimary
outcomewithrhythmand/orheartratecontrolwasachievedin13patients
(93%).All4patientswithreentrantSVThadresolutionoftheirtachyarrhythmia.
OnepatientwithAET(220to270beats/min)respondedwell,withadecreasing
heartrateto120beats/minwithin35minutesandsinusrhythmwithin85
minutes.Accordingtothispreliminaryobservationalreport,dexmedetomidine
mayhaveapotentialtherapeuticroleintheacutephaseofperioperativeatrial
andjunctionaltachyarrhythmiasforeitherheartratecontrolorconversionto
sinusrhythm.
ThusSVTcancomplicatethemanagementofpatientsundergoingcongenital
heartdiseasesurgery.Atrialandjunctionaltachyarrhythmiasoccurfrequently
duringtheperioperativeperiod,increasingperioperativemorbidityand
mortality.Theserhythmdisturbancesmaybewelltoleratedbyanormalheart
butcancausesignificanthemodynamicinstabilityinpatientswithcongenital
heartdefects,particularlyduringtheperiodfollowingcardiopulmonarybypass.
Asthispopulationages,AFandflutterbecomethearrhythmiasofinterest.A
preoperativemanagementstrategyshouldincludeablationifchildrenwheresize
limitationsandtachycardiasubstratesallow.Preoperativeamiodaronemight
offerawaytomakepostoperativeAFlessproblematic,andoperativeablation
surgeryshouldbeconsideredwhenapplicable.
VentricularTachycardia
Scarring,hypertrophy,anddilationarethethreeprincipalcausativefactors
contributingtopostoperativearrhythmias,includingbothSVTandVT.The
immediatepostoperativeperiodfollowingsurgeryforcongenitalheartdiseaseis
atimeofuncertaintyplaguedbyalterationsinhemodynamics,electrolyte
disturbances,andutilizationofpotentiallyarrhythmogenicinotropes.An
understandingoftheanatomicsubstrate,potentiallypreexistingarrhythmias,as
wellastheoperativeprocedureiscriticalinplanningtheacuteandpotentially
long-termmanagementstrategies.Withallpostoperativearrhythmias,itisof
utmostimportancethatthecardiologistandintensivistunderstandtherepairand
residualhemodynamiclesions,ifany.TheacutemanagementofVTinthe
postoperativesettingshouldaddressanyelectrolytedisturbancesand,ifpossible,
reduceanyproarrhythmicdrugs,suchasinotropes,ifpermissible.
AcutemanagementofVTinthepostoperativeperiodissimilartotheacute
managementofVTinanyhospitalsetting.Ifthepatientisstablewithsustained
VT,obtaininga12-leadECGisoftenhelpful,especiallysoastocompareitwith
apreoperativeECG.Ifthepatientisunstable,withhypotensionorlowcardiac
output,cardioversion(1to2synchronizedcardioversion)shouldbeimmediately
considered.IfthepatientisstablewithVT(monomorphic),lidocaineor
amiodaronemaybeconsidered.Thedecisionforchronicantiarrhythmic
managementshouldbepredicatedonwhethertherewasaneasilyreversibleand
explainablecausefortheacuteVT.Ifthereisnot,mostpatientsshouldundergo
adetailedevaluationoftherepair,eitherwithadvancedmultimodalityimaging
orcardiaccatheterization.Long-termpreventionofsymptomaticVTcanbe
challenging.Optionsforchronicsuppressioninclude(1)antiarrhythmic
medicationswithserialnoninvasive(Holterandstresstest)examinationsto
assessreliability;(2)antiarrhythmicmedicationswithinvasive
electrophysiologystudiestoassessreliability,(3)ICDimplantation,or(4)
detailedthree-dimensionalmappingoftheVTcircuitwithcatheterablation.
Newadvancesinthree-dimensionalmappingandautomatedmappingmakethis
lastchoicemoreappealingthanrelyingonchronicmedications,whichmaynot
beasfullyprotectiveagainstrecurrentevents.
PatientswithpolymorphicVTorTdPpostoperativelyareextremelyhigh-risk
patientsforongoinglife-threateningarrhythmiasandshouldbeconsideredforan
ICD.InpatientswithhemodynamicallyconcerningpolymorphicVT,TdP,
recurrentmonomorphicVT,orVFshouldundergoadetailedhemodynamic
catheterizationoradvancedmultimodalityimagingtoassesstherepairandmake
surethatthereisnotasignificantresiduallesionthatiscausinguntoward
hemodynamicsandprovokingamalignantarrhythmia.TdPmayoccurinthe
settingofQTprolongationanddrugsthatmightotherwisebeused
(procainamide,amiodarone,sotalol)shouldbeavoidedinTdP,astheywilllikely
increasetheQTintervalfurther;treatmentmayconsistofintravenous
magnesiumsulfate(25mg/kgover5to15minutes),lidocaine(1mg/kg
followedbyaninfusionof20to50µg/kgperminute).IfthetriggeroftheTdP
iscatecholaminesensitivity,intravenousesmololisoftenhelpful.Ifthetrigger
fortheTdPisrelatedtoabruptpausesinthenormalheartrate(long-shortcycle
lengths),pacingorinfusedisoproterenol,bothofwhichshortentheQTinterval,
maybemorehelpfulinthissetting.Cardioversionisofnovalueinpatientswith
salvosofnonsustainedVTandcanevenaggravatethetachycardia.
PatientswithVFshouldbetreatedimmediatelywithdefibrillationat2J/kg.
Inaddition,patientswhohaveundergonecardioversionordefibrillationshould
beimmediatelydiscussedwiththecardiaccareteam,includingthecardiac
surgeon,regardingproactiveplanstoconsiderVAextracorporealmembrane
oxygenationuntilthehemodynamicsimprove.
