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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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Citethisarticle:TwoMRICompatibleICDsPassSafetyandEfficacyHurdles.Medscape.May15,2015.