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May15,2015
BOSTON,MATwonewimplantablecardioverterdefibrillators(ICDs)modifiedforMRIpassedamajorhurdlewheninvestigatorsreportedtheMRIscannerdidnotadverselyaffectdeviceperformanceorthetreatmentofventriculararrhythmias.[1,2]
"ICDsarecontraindicatedforMRI,andithasbecomeanimportantproblem,"saidDrMichaelGold(MedicalUniversityofSouthCarolina,Charleston),leadinvestigatoroftheEveraMRIStudy."Forevidenceofhowthatcanrestrictpatientcare,ifwelookatthestrongestindicationforanMRI,whichisafterastroke,weknowthatpatientswithICDsare50foldlesslikelytohaveanMRIfollowingastrokethanthosewithoutanICD.ThereisaclearneedfordevicesthatareMRIsafe."
PresentingtheresultshereattheHeartRhythmSociety(HRS)2015ScientificSessions,GoldsaidthereareseveralpacemakersonthemarketthatareMRIsafebutthereisstillnoICDconsideredsafefortheimagingscan.Thedevicetheresearcherstested(Evera,Medtronic)isasingleordualchamberICDmodifiedwithchangestothefirmwareandhardwaretomakeitcompatiblewiththeMRIscan.IntheEveraMRIstudy,275patientswereimplantedwiththeMRIcompatibleICDandrandomizedtoaseriesoffullbodyMRIscansincludingscansofthechest,thoracicspine,cervicalspine,andheadortothecontrolarm.
"Theresultsofthestudywereveryreassuring,"saidGold."ZeropatientsinthewholestudyhadacomplicationassociatedwiththeMRI.Therewas100%successofmeetingthesafetyendpoint."
Inasecondstudy,DrKhaledAwad(UniversityofAlabamaBirminghamSchoolofMedicine)presenteddataonasecondICD(Iforia,Biotronik),alsocompatiblewithMRIscanners.Among170ICDpatientsenrolledinthesinglearmProMRIstudy,154underwentnonclinicallyindicatedthoracicspineMRIscansand25.7%hadacardiacMRI.Onemonthaftertheprocedure,thedevicewastestedandinvestigatorsreportedequallygoodresults.
"Wedidntdetectanysignificantchangestothepacingandsensingparameters,"saidAwadatanHRSpressconferenceannouncingtheresults."Mostimportant,therewasno[effect]ontheICDs'mainfunction,whichisthedetectionandtreatmentofventriculararrhythmias.Ofallthepatientsthathadepisodesoflifethreateningventriculararrhythmias,allwereappropriatelydetectedandtreatedwiththedevice."
Tothemedia,AwadsaidtheadvancementofMRIcompatibleICDsshouldchangetheregulatoryfieldintheyearstocome.SuchregulatorychangeswouldeventuallyallowfortheroutineuseofMRIimaging,includingcardiacandthoracicMRIs,forpatientswhohaveoneofthesenewerdevices."Thedataarecertainlysimilarandshowsimilarresults,"saidAwadoftheBiotronikandMedtronicMRIcompatibleICDs."TheyconfirmwhatweknowthatifyoudesignasystemplatformspecificallyforMRI,itshouldperformwellinanMRIenvironment.Hopefullythiswillopenthedoorforanewerawheremostofthedevicesaredesignedtothemeet[theMRIcompatible]standard."
Interestingly,patientsintheUnitedStatesarecurrentlybeingimplantedwiththeBiotronikMRIcompatibleICD,butthedeviceisnotyet"turnedon"tomakeitMRIsafebecausethosefunctionsarenotyetapprovedbytheUSFoodandDrugAdministration(FDA).AwadsaidthattheMRIfunctionalityislockedandinaccessibletoMRIprogrammersuntilitreceivesFDAapproval.IfandwhentheFDAapprovestheMRIcompatibledevice,thecustomprogrammingrequiredtomakethedevice"mute"intheMRIscannerwouldthenbeavailabletophysicians,saidAwad.
TwoStudies,BothExcellentResults
IntheEveraMRIstudy,investigatorsalsomeasuredanypotentialchangestotheventricularpacingcapturethreshold(VPCT)fromthebaselinetestto1monthfollowingtheMRIscan.Overall,therewasnodifferencebetweentheICD
TwoMRICompatibleICDsPassSafetyandEfficacyHurdlesMichaelO'Riordan
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patientswhounderwentMRIandthecontrolgroupwhodidnot.OnlyonepatientinthestudyhadanincreaseinVPCTof0.5Vorhigherandthatpatientwasinthecontrolarm,saidGold.
ResearchersalsolookedatthedetectionofventriculararrhythmiasfollowingtheMRI.Inall,therewere34episodesofspontaneousorinducedventriculartachyarrhythmias/ventricularfibrillationin24patients,butinvestigatorssawnodelayinthedetectionandtreatmentoftheevent.Followingthecompletionofthestudy,12oftheenrolledpatientsunderwentMRIsforclinicalreasonsandtherewerenoMRIrelatedcomplications.
Speakingduringthelatebreakingclinicaltrialsession,GoldsaidpatientswithnonMRIcompliantICDshaveundergonescansatselectedclinicalcenters,butthereareoftenrestrictionsonthetypeofMRIthatcanbeperformed.TherearealsotheoreticalandprovenhazardsofMRIsinpatientswithanICDandpacemakers,includingthepotentialforpatientdiscomfortcausedbyforceandtorquegeneratedbythemagneticfield.Themostworrisomesideeffectsareunintendedcardiacstimulationorleadelectrodeheating.
"I'mnotsureweknowwhatthespecificcomplicationratesare,"GoldtoldheartwirefromMedscape."TherearecertainlycasereportsofpatientswholosepacingandtherehavebeendeathsreportedwithpatientsreceivingMRIswith[nonMRIsafe]devices.Thosetendtobeolderdevices.Therearereportsofpacingthresholdsgettingveryhighwhereit'sdifficulttopaceduringanevent.ThecentersthatdoMRIsonpatientswithdevicesthatarenotMRIcompatiblewillrestrictthemtopatientswhoarenotpacingdependentorwillnotdoMRIsonthechestarea."
DrJonathanKalman(RoyalMelbourneHospital,Australia),moderatorofthelatebreakingsession,saidtheissueofMRIcompatibilitywithimplantabledevicessuchasICDsandpacemakersisnotatrivialonegiventhatdeathswithnonMRIsafeICDshavebeendocumented.Atpresent,hesaid,whatisnotknownabouttheMedtronicMRIsafeICDisexactlywhatmakesitsafegiventhatthedesignisproprietary.
"Buttohavetodonethisstudy,withthistypeofdevice,wecannowsaythatwecandothissafely,"Kalmantoldheartwire."ThatisaverybigadvancefordefibrillatorpatientsbecausenoMRIscanner,anywhereintheworld,wouldacceptapatientwithanimplantabledevice.Therewereveryspecificexceptionsanditwascertainlynotroutine.Ithinkthisisextremelyimportant."
In2014,however,thepresentationofdatafromalargeregistryappearedtochallengetheconventionalwisdomofdenyingdiagnosticnonthoracicMRIscansinpatientswithconventionalpacemakersorICDs.Asreportedbyheartwire,DrRobertRusso(ScrippsResearchInstitute,LaJolla,CA)presenteddatafromtheMagnaSafeRegistryattheAmericanHeartAssociation(AHA)2014ScientificSessions,concludingthataclinicallyindicatednonthoracicMRIofthebrain,lowerspine,hip,orkneecouldbedoneinpatientswithconventionaldevicesatnorisktothepatient.
GoldnotedthattheseriesofMRIsequencesinthepresentstudywereintendedtobeclinicallyrelevantbutnotdesignedtoproduce"beautifulMRIimages."ThestudywasintendedtostresstheICDinstead,hesaid.
Goldhasreportedconsultingfees/honorariafromBiotronik,StJudeMedical,BostonScientific,andMedtronic.Disclosuresforthecoauthorsarelistedintheabstract.Awadhasreportednorelevantfinancialrelationships.Disclosuresforthecoauthorsarelistedintheabstract.
References
1. GoldMR,SommerT,SchwitterJ,etal.TheEveraMRIstudy.HeartRhythmSociety2015ScientificSessionsMay14,2015Boston,MA.AbstractLBCT0106
2. AwadK,GriffinJ,CrawfordTC,etal.ClinicalsafetyoftheIforiaProMRIICDsystemsubjectedto1.5TcardiacorthoracicspineMRI.HeartRhythmSociety2015ScientificSessionsMay14,2015Boston,MA.AbstractLBCT0204
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HeartwirefromMedscape2015Medscape,LLC
Citethisarticle:TwoMRICompatibleICDsPassSafetyandEfficacyHurdles.Medscape.May15,2015.