Andersons pediatric cardiology 567
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resultintheneedtoundergoleadextraction,andthereforetheconceptof
leadlesspacemakershasbeendeveloped.Differentdevicecompanieshave
developedleadlesspacingmodelsthathavebeenimplantedinadultswith
varyingresults.Thepacemakersystemisdeliveredviathetranscatheter
approachandallelectrodesarefullycontainedinasingleunitthatisimplanted
intheRVapex.Seriousdevice-relatedcomplicationsrangedfrom6.7%to
18.6%.201Currently,leadlesspacemakerimplantationisnotroutinelyperformed
andtherearenostudiesinchildren.
CompatibilityofMagneticResonanceImaging
Thereisagrowingpopulationwithimplantedelectroniccardiacdevicesanda
paralleldemandforMRI.Formostimplantedhardwarethereisalargely
theoreticalconcernthatexposureunderthestrongelectromagneticfields
encounteredduringMRImayresultinshiftingofthedevice,heatingofthe
hardware,changesintheprogrammedsettingsenablingasynchronouserratic
rapidpacing,triggeredtachyarrhythmiatherapies,orpacinginhibition.Device
companieshaveundergonelabor-intensivetrialstodevelopMRI-safedevices
forthegrowingneedsofthesepatients.Althoughsomeofthemorerecent
devices(implantableloopmonitors,pacemakersandICDs)areMRI-conditional,
riskfactorsremain.Protocolshavebeendevelopedandcenteronutility
shielding,filters,andbipolarleadstomitigateelectronicinterference;device
programmingprotocols;andimagetipsandguidelinestopreventartifactacross
theareaofinterest.Carefulselectionoftherighttestfortherightpatientwith
therightimplantedhardwareisparamountinpromotingsafetyandstrategiesto
optimizecare.202ItisimportanttorememberthatMRI-conditionaldevices
includenotjustthegeneratorbutalsotheactiveleadsaswellaschronically
abandonedleadsthatmaybeendocardial,epicardial,oracombinationofthe
two.ArecentguidelinepublicationbytheHeartRhythmSocietyfocusedon
recommendationstargetingtheclinicalaspectsofsafetywithMRInonconditionalandconditionalsystems.203
PacemakerSyndrome
TheconsequencesofatrialcontractionagainstclosedAVvalvesduring
ventricularsystolecreatetransientincreasesinatrialpressure.Thesymptoms
thatrelatetosuchaphysiologiceffectincludefatigue,exerciseintolerance,a
sensationoffullness,dyspnea,andheadache;theyhavefallenunderthebroader
headingofpacemakersyndrome.Thisoccursinupto20%ofpatientswith
single-chamberpacingfromlossofAVsynchrony,butisnotrestrictedtosinglechamberdevices.204Thesesymptomscansometimesbyimprovedbyadjusting
theprogrammedsettingsofAVintervalsandrate-adaptivefeatures.Ifsymptoms
persist,otheroptionsmaybeexplored,includingupgradingtoadual-chamber
systeminthosewithasingle-chambersystem.
RoutineFollow-Up
Afterpacemakerimplantation,ongoingcarefulfollow-upisnecessary.Thiswill
varytosomedegree;however,commonpracticeistoevaluatenewimplantsina
patientat2weeksandat3months.Followingthis,visitscanbespacedoutto
every3to12months,eitherinpersonorwithremotemonitoring.Initial
postimplantevaluationisdonetoruleoutcomplicationssuchaspneumothorax,
hemothorax,pacemakerpockethematoma,cardiacperforation,pleuralor
pericardialeffusionleaddislodgement,diaphragmaticstimulation,infection,
pacemakermalfunction,centralvenousthrombus,leadfracture,insulationbreak,
orTwiddlersyndrome,althoughthesearerare.Remotemonitoringisbeneficial
indecreasingtheneedforin-officeevaluationandhasmultipleotherbenefits,
includingimprovedcareandconveniencetofamilies.Subsequenttotheacute
postimplanttimeperiod,itisvaluablealwaystoreevaluatethepatientspacing
requirementswhiletestingthedeviceandtobeopentoalteringprevious
programmedmodes,sincethepatient'sclinicalstatusmaychange.Routine
evaluationshouldincludeassessmentofbatterystatus,pacingthresholds,pulse
width,sensingfunction,theintegrityofthelead,anysensedorrecordedevents,
andsurveillanceforanyoccultarrhythmias.
RestrictionsforPatientsWithImplantedDevices
Riskfactorsinvolvedinlivingasedentarylifesurpasstheriskfactorsof
possibledamagetothedevicehardware.Providersshouldencouragepatientsbe
activeandstayhealthy.Decisionsregardingthelevelofactivityshouldbe
individualizedtowardpatientswithunderlyingheartdisease,underlyingrhythm
disturbances,andthepossibilityofthedevelopingatachyarrhythmia.
Participationinorganizedteamsportsshouldbeaninformedcollaborative
decisionbetweenthecardiologist,parents,andpatient.Inthecaseofpatients
whoarepacemakerdependent,meaningthattheydonothaveanadequate
underlyingrhythmtosustaintheircardiacoutput,activityrestrictionsare
needed.Varyingopinionstoprotectthisvulnerablepopulationinvolve
increasingsafetymargins,addinganadditionalventricularlead,orplacing
biventricularsystems,buttherearenocleardatatoguidethisdecision.
