Jared Bunch MD Heidi T May PhD MSPH Tami L Bair BS J Peter Weiss MD Brian G Crandall MD Jeffrey S Osborn MD Charles Mallender MD Jeffrey L Anderson MD Brent J Muhlestein MD Donald L Lappe MD John D Day MD FHRS From the Intermountain Heart Institute ID: 53106
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brillationablationpatientshavelong-termstrokeratessimilartopatientswithoutatrialbrillationregardlessofCHADS2scoreT.JaredBunch,MD,HeidiT.May,PhD,MSPH,TamiL.Bair,BS,J.PeterWeiss,MD,BrianG.Crandall,MD,JeffreyS.Osborn,MD,CharlesMallender,MD,JeffreyL.Anderson,MD,BrentJ.Muhlestein,MD, DrBunchhasservedasaconsultantforBiosenseWebster,StJudeMedical,andBostonScienti Inpatientswithlowtomoderateriskafterablation(CHADS2score2),thecalculatedstrokeriskis0.06%peryeartreatedwithlong-termantiplatelettherapyonly.Potentialmechanismsofstrokereductionafterablationhavenotbeenelucidated.ItisplausiblethattheobservedbenetrelatestoloweringAFburdenandfavorableremodel-ingoftheleftatriuminthosepatientsinwhichAFcausedatrialmyopathy.However,itisalsoplausiblethatmorepatientsorlessriskypatientsareselectedforablationproceduresthatinherentlyhavealowerstrokerisk.Inthisregard,wewouldnotanticipateabenetinhigherriskstrokepatientsafterAFablation.TofurtherunderstandtheeffectofAFablationonstrokerisk,weexaminedthelong-termriskofstrokeafterablationcomparedtoAFpatientswhodidnotundergoablationandnon-AFpatientsandspecicallyevaluatedthepotentialbenetacrossallCHADS2riskstrata.PatientpopulationsThreecohortsofpatientswerestudied:patientswithAFwhohadundergoneablation,patientswithAFwhodidnotundergoablation,andpatientswithoutahistoryofAF.AblationpatientsweredrawnfromthelargeongoingprospectiveIntermountainAtrialFibrillationStudyRegistry,whichcom-prisesallhealth-carefacilitieswithintheIntermountainHealthcarenetwork.PatientswhounderwentablationfromallIntermountainHealthcarefacilitiescapableofperformingAFablationwereincluded.Theablationapproach,postabla-tionanticoagulationstrategy,andfollow-upscheduleweredeterminedbythepatientselectrophysiologistandnotbyasystem-wideprotocol.Controlpopulations,patientswithAFwhodidnotundergoablation,andanoAFpopulationwerematched4:1byage(2years)andsextoAFablationpatients.ThelatterpatientswerefoundtohavenohistoryofAFthroughtheexaminationofallclinicalnotes,InternationalClassicationofDiseases,NinthRevisionICD-9)diagnosiscodes,andthesystem-wideelectrocardiogramdatabase.Thesepatientsofwhomwehadatleast3yearsoffollow-updatacomprisethosepreviouslystudiedinthegeneraloutcomesstudyreport.Theenrollmentperiodsforthesepatientswereasfollows:NoAF:September9,1993,toNovember24,2009;AF,noablation:January12,1984,toNovember4,2009;andAF,ablation:January15,1999,toNovember2,2009.TheIntermountainHealthcareUrbanCentralRegionInstitutionalReviewBoardapprovedthisstudy.Otherriskfactors,demographics,andpatientfollow-upandeventassessmentInadditiontoageandsex,patientinformationcollectedincludeddiabetes,hypertension,hyperlipidemia,heartfail-ure,andrenalfailure.TheseriskfactorsweredeterminedbyICD-9diagnosiscodesatorbeforetheindexdate.Priorcerebrovascularaccident(CVA),transientischemicattack,andmyocardialinfarctionweredeterminedbyusingdischargediagnosiscodes.Themeanlengthoffollow-upwas2.92.9years.TheprimaryoutcomeofinterestwasCVA(referredtohereinasstroke)andwasdeterminedthroughtheexaminationofdiagnosiscodes:436*,433._1*,and434._1*.TheStudenttestandthetestwereusedtoevaluatebaselineandclinicalcharacteristicsamongpatientswithandwithoutAF.MultivariableCoxhazardregressionanalysis(SPSS,version15.0)wasusedtoevaluatetheassociationofAFwiththeincidenceofthestudyendpoint.ForeachCVA,amodelwasdevelopedthatincludedonlyconfoundingandcantcovariables.Covariablesincludedbaselineriskfactors,identiedthroughICD-9diagnosiscodes,thatweredocumentedeitheratorbeforetheindex(baseline)dateTable1).Allcomorbiditieswerebaselineandpredatedtheendpoints.Fortheablationgroup,demographicswerecollectedatthetimeoftherstdocumentedablationprocedure.Finalmodelsenteredthesignicant(andconfounding(10%changeinhazardratio)covariables.valuesof.05weredesignatedtobenominallysignicant.ABonferroni-adjustedvalueof.025(0.05/2)willbedeemedassignicantintheregressionanalysestoaccountformultiplecomparisons(AF,noablationvsnoAFcohortsandAF,ablationvsnoAFcohorts).WeestimatedsurvivalfreeratesbyusingtheKaplan-MeiermethodforCVA.CVArateswerefurthercomparedbyusingCHADS2strata.Atotalof37,908patientswereincludedinthestudy.Thisincluded4212patientswhounderwentacatheterablationfor Table1BaselinedemographicsofthestudypopulationNoAFAF,noablationAF,ablationAge(y)64.113.066.013.364.8Sex:male60.8%60.8%60.8%Hyperlipidemia58.4%37.3%44.0%Hypertension41.2%45.3%47.8%Diabetes19.0%21.1%16.3%Heartfailure14.5%23.6%29.5%Renalfailure5.6%7.8%7.5%MIhistory10.0%6.4%6.4%TIAhistory4.0%4.2%4.6%CVAhistory4.4%6.3%4.5%Valvehistory10.9%14.8%27.7%CHADS2score041.0%35.7%38.7%128.3%26.6%24.9%217.9%18.2%16.5%38.6%11.5%12.2%42.9%5.1%5.2%51.2%2.3%2.0%60.2%0.6%0.5%EF(n10,004)60.016.056.115.951.3brillation;CVAcerebrovascularaccident;EFfraction;MImyocardialinfraction;TIAtransientischemicattack. BunchetalAFPatientswithLong-TermStrokeRates symptomaticAF.Asecond4:1matchedpopulationwascreatedofpatientswithAFwhohadahistoryofAFanddidnotundergocatheterablation(n16,848).Finally,athird4:1matchedpopulationwascreatedofpatientswithnoclinicalorelectrocardiographichistoryofAF.Thebaselinedemographicsofthese3groupsarelistedinTable1.ThenoAFgroupwasyoungerandhadlowerratesofhypertension,heartfailure,renalfailure,andvalvedisease.05)comparedtotheother2groups.TheAFgroupwhodidnotundergoablationwasslightlyolderandhadahigherrateofdiabetesandapriorstroke(.05).TheAFablationgrouphadhigherratesofhypertension,transientischemicattack,andvalvularheartdisease(.05).TheCHADS2riskprolesweresimilaramonggroups;however,morepatientswithnohistoryofAFhadscoresfrom0to1.At1year,893(2.4%)patientshadastroke.TherewasacantlyhigherrateinthosepatientswithAFwhodidnotundergoablation(3.5%,n590)comparedtothosewithAFwhounderwentablation(1.4%,n61)andthosewithnohistoryofAF(1.4%,n242)(Theratesbetweenthosewhohadablationandthosewithnohistoryofablationwereidentical.TheriskofstrokeinAFpatientsnottreatedwithablationcomparedtothosetreatedwithablationremainedsignicantinunivariate(oddsratio[OR]2.49;.0001)andmultivariate(OR2.06;.0001)adjustment.TheequivalenceinthisoutcomebetweenAFpatientstreatedwithablationandthosewithnoAFremainedwithbothunivariate(OR1.01;.95)andmultivariate(OR0.95;.74)adjustment.Thedemo-graphicsofthosepatientswhohadastrokeduringtherstyearoffollow-uparelistedinTable2.TheCHADS2riskfactorsamongthegroupswererelativelyevenlydistributed.20).ThenoAFgroupwasslightlyyoungerthantheothergroups,andAFpatientswhounderwentablationmoreoftenwerelabeledashavingvalvedisease.Wethenexaminedlong-termstrokebyageamongAFpatients.TheresultsarelistedinTable3.Inallagegroupstrata,therewerelowerstrokeratesinAFpatientswhounderwentablationcomparedtothosewhodidnot.Finally,wesoughttodeterminewhetherabenetregardinglong-termriskofstrokewasobservednotonlyacrossallagegroupsbutalsoacrossthespectrumofCHADS2riskproTable4Figure1displaysKaplan-MeiersurvivalcurvesoffreedomfromstrokebasedonAFstatusandtreatmentandCHADS2riskscore.Figure2displaysthemultivariateadjustedhazardratiosfortheriskofstrokeinpatientswithAFwhounderwentablation,patientswithAFwhodidnotundergoablation,andnoAFpatients.Figure3displaysthemultivariateadjustedhazardratiosfortheriskofstrokeinpatientswithAFwhodidnotundergoablationversusthosewithoutAF.Ingeneral,acrossallagesandriskproles,therewasalowerriskofstrokeaftercatheterablation.OfthebaselinedemographicsintheAFablationgroup,ahistoryofstrokewastheriskfactormostassociatedwiththefutureriskofstroke(OR11.9;Figure4displaysthemultivariateadjustedhazardratiosfortheriskofstrokeinpatientswithAFwhounderwentablationandinpatientswhohadnohistoryofAF.Acrossallageandriskstrata,theriskofstrokewassimilarinthese2groups.AFablationpatientshaveasignicantlylowerriskofstrokecomparedtoAFpatientswhodonotundergoablation.Thelowerriskspansacrossallagegroupsstudiedwiththemostcantbenetobservedinyoungerpatients.Further-more,theobservedreductioninstrokepersistsacrossallCHADS2riskproMorecompellingarethedatacomparingAFpatientswhoundergoablationtopatientswithnoidentiablehistoryofAF.WepreviouslyfoundthatAFincreasesriskofstrokeacrossallCHADS2riskprolescomparedtopatientswithnohistoryofAF.Inaddition,amongpatientswhopresentforAFablation,theCHADS2riskfactorsalsoincreasethelikelihoodofecho-contrastsludgeandclotintheleftatrialappendageaswellasreductionintheappendageemptyingvelocities:echocardiographicndingssuggestiveofahigherriskofstroke.Theage-andCHADS2risk-proledatathatcomparedpatientswhounderwentablationwithpatientswithnohistoryofAFfoundlong-termriskofstrokeweresimilar.Thesedatainpartsuggestthatablation,andtheprocessandsubsequentcareassociatedwithablation,canfavorablyaffectthenaturalhistoryandconsequencesofAF.However,itmustbeemphasizedthatsincethesedataarederivedfromamulticenterobservationdesign,wedonothaveaccuratedataonlong-termsuccessratesofAFrecurr-ence,particularly,subclinicalAF.Assuch,wecontinuetoadvocatelong-termstrokepreventionstrategiesbasedonthe Table2BaselinedemographicsofAFandnon-AFpatientswhoexperiencedastrokeat1yCharacteristicNoAFAF,noNo.ofpatients24259061Age(y)67.012.470.811.070.0Sex:male53.3%51.5%47.5%.71Hyperlipidemia59.1%35.3%50.8%Hypertension56.6%55.8%65.6%.34Diabetes29.3%27.8%23.0%.61Heartfailure23.1%30.7%45.9%.002Renalfailure7.4%8.8%11.5%.58MIhistory9.5%7.8%16.4%.07TIAhistory16.1%11.9%9.8%.19CVAhistory40.9%37.8%31.1%.35Valvehistory20.2%19.8%42.6%CHADS2score.20016.9%16.6%19.7%116.5%19.2%19.7%221.1%18.0%4.9%323.1%18.6%24.6%412.0%16..8%19.7%59.5%9.2%8.2%60.8%1.7%3.3%EF(n148)57.916.051.021.554.710.5.40brillation;CVAcerebrovascularaccident;EFfraction;MImyocardialinfraction;TIAtransientischemicattack. HeartRhythm,Vol10,No9,September2013 CHADS2score,regardlessofwhetherablationwasper-formed,untilprospectivedataareavailable.ThecompellingquestionremainingishowAFablationchangesthenaturalhistoryofAFasitrelatestoCVA.TypicallyAFseverity,mosteasilyquantiedasepisodesanddurationofAF,willincreaseovertime.Theprogressionisnotuniform,andnotallpatientswhodevelopparoxysmalAFwillprogresstopersistent/long-standingpersistentAF.AstheatriumisrepetitivelyexposedtoAF,earlyatrialcontractileremodelingoccurs.IfAFpersists,structuralremodelingdevelops.Permanentchangesoccurasfocalandthenregionalbrosisdevelopintheleftatrium.structural,anatomic,andfunctionalchangesareallassoci-atedwithstrokeinpatientswithAF.Itispossiblethatablationearlyinthediseaseprocess,byeithermaintainingsinusrhythmorsignicantlyreducingAFburden,canstoptheprogressionofthestructural,anatomic,andfunctionalchangesintheatrium.Thispostulateissupportedbyserialechocardiographicassessmentsofatrialfunctionovertimeafterablaton.ClearlytherearerisksassociatedwithAFablation,whichmayalsoincreasestrokerisk.AFablationcausesintentionalbrosisintheleftatrium;iftheinjuryissignicant,itcancausemechanicaldysfunction.Also,thereisriskofperiproceduralstroke,inparticularsubclinicalstroke,whichasofyetisnotfullyunderstoodandquantiTheserisksarelikelymodiablebylimitingtheextentoftheablationperformedandbycarefulandcontinuoususeofanticoagulation.Anotherpotentialadvantagewithcatheterablationisreducingdependencyonantiarrhythmicmedicationsforlong-termrhythmcontrol.Long-termpharmacologicman-agementcanbechallenging,particularlyasthepatientTherearechangesinmetabolism,drugclearance,and,withtheacquisitionofadditionalcardiovasculardis-eases,thepotentialfordrug-to-druginteractions.Thesechangescanalterapatientsfunctionalstatusandalsotheriskfor,useof,andpatientselectionforanticoagulation.Assuch,althoughcatheterablationhassignicantrisks,theseriskstypicallyarerealizedupfrontwiththeprocedurewhereasthosewithmedicationsareobservedcontinuallyovertime.AnotherpossibilityisthatpatientswhohaveablationmaybemoreaggressiveaboutaddressingtheirAFriskandassucharemorelikelytoalsoreceivetreatmentforotherriskfactorsofstroke,suchashypertension,diabetes,andheartfailure.Forexample,thepresenceofheartfailure,apotentiallymodiableriskfactor,inpatientswithAFpresentingforablationwasthemostcommonlyassociatedvariablethatresultedinthepresenceofleftatrialappendagemechanicaldysfunction,appendageclot,andsludge.Thisislikelynottheonlymechanism,asweobservedabenetwithAFablationacrosstheentirespectrumofCHADS2riskscores,includingpatientswhohadacquiredmanydiseasestates.ThereisalsothepossibilitythatmoretorhealthypatientsarechosenforAFablation.Assuch,theyarelesslikelytoexperiencemorbidityandmortalityassociatedwiththedisease.Forthisreason,weperformedthisrisk-stratistudyandfoundthattherewasapervasivestroke-relatedtacrossallriskfactorsthatweassessed.Nonetheless,theobservationalstudydesignusedcannotcompletelyexcludethispossibilityasamechanismbehindtheobservedStudylimitationsOurstudyhasseveralimportantlimitations.Thestudyisobservationalandmaybesubjecttoincompletecorrectionforimportantcovariablesandconfounders.Thestudyis Table3Age-basedlong-termstrokeratesamongAFpatientswhounderwentablationcomparedtothoseAFpatientswhodidnotunderwentAgeAF,noablationAF,ablationUnivariateHRforablationMultivariateHRforablation60,n56383.6%1.3%.00010.38,.00010.38,69,n58045.6%2.9%.00010.50,.00010.59,79,n70828.7%3.8%.00010.42,.00010.50,80,n25368.6%5.8%.070.55,.0090.72,brillation;HRhazardratio. Table4CHADS-2scorebasedlong-termstrokeratesamongAFpatientswhounderwentablationcomparedtothoseAFpatientswhodidnotundergoablationCHADS2NoAFAF,noablationAF,ablation02.6%(178of6902)3.7%(220of6017)1.6%(26of1628)13.0%(144of4772)5.4%(243of4477)1.9%(20of1050)24.3%(129of3015)7.1%(217of3072)2.2%(15of696)37.4%(108of1452)9.0%(174of1939)6.1%(31of512).06410.7%(52of484)17.6%(152of864)9.1%(20of220)513.9%(31of223)18.6%(89of479)13.2%(14of106).18 BunchetalAFPatientswithLong-TermStrokeRates derivedfromalargeconsecutivepopulationofAFpatientsandnoAFpatientswithlong-termfollow-up.Inaddition,theonlyinclusioncriteriafortheAFablationpopulationwerethatwehadavailablelong-termfollow-upinformation.Allotherprocedurevariablesandfollow-upstrategieswereincluded,asweusedpatientsfromallmultiplecentersinwhichtheprocedurewasperformed.Forthecontrolpop-ulation,attemptsweremadetomatchvariablesinawaythatdemographicsweresimilarinordertoallowamorespeciunderstandingoftheroleofAFtreatmentandoutcomes.Anotherlimitationisthatwehavenodataavailableinthelargepopulationregardinganticoagulationstrategy,compli-ancetoanticoagulation,orphysicianadherencetoguidelinesregardinganticoagulation.Ithasbeenthegeneralpracticeintheseinstitutionstousewarfarinorasimilaranticoagulantlong-termiftheCHADS2scoreis2regardlessoftherhythmcontrolstrategy.Decisionstointerruptorchangeanticoagulationstrategiesoutsidethecurrentguidelinesshouldonlybemadeonthebasisofprospectiverandomizeddatawhenitbecomesavailable.Finally,weuseddiagnosiscodestodetermineCVA,andassuchwerecognizethatthiscanbesubjecttooccasionalmisdiagnosis.We Figure3Multivariatehazardratios(HRs)aredisplayedforpatientswithbrillation(AF)whodidnotundergoablationversuspatientswithnoknownhistoryofAF.AnHR1.0indicatesanincreasedriskofstrokeinAFpatientsnottreatedwithablation.HRsaredisplayedbyageandCHADS2riskscores.Acrossallcategoriesandsubcategories,HR1.0arenotedinAFablationpatientswhodidnotundergoablation. Figure1Kaplan-Meiersurvivalestimatesaredisplayed.Thesurvivalcurvesaredisplayedin3groups(atrialbrillation[AF]noablation,AFablation,andnoAF)andcomparedbyCHADS2riskscore(01,2Inallcomparisons,patientswithAFwhodidnotundergoablationhadearlyandpersistentlowersurvivalfreeofcerebralvascularaccident(stroke)comparedtoAFablationpatientsandpatientswithoutAF.AFablationandnoAFpatientshadsimilarsurvivalcurves.CVAcerebrovascular Figure2Multivariatehazardratios(HRs)aredisplayedforpatientswithbrillation(AF)whodidnotundergoablation(top3)andAFpatientswhounderwentablation(bottom3)versuspatientswithnoknownhistoryofAF.AnHR1.0indicatesanincreasedriskofstrokeinAFpatientsnottreatedwithablation.HRsaredisplayedbyCHADS2riskscores.Acrossallcategoriesandsubcategories,HR1.0arenotedinAFablationpatientswhodidnotundergoablationversusnoAFpatients.Acrossallcategoriesandsubcategories,HRcrossed1.0inAFablationpatientsversusnoAF Figure4Multivariatehazardratios(HRs)aredisplayedforpatientswithbrillation(AF)whounderwentablationversuspatientswithnoknownhistoryofAF.AnHR1.0indicatesanincreasedriskofstrokeinAFpatientstreatedwithablation.HRsaredisplayedbyageandCHADS2riskscores.Acrossallcategoriesandsubcategories,nosignicantincreaseinriskwasfoundfortransientischemicattackorstrokedespitethepresenceofAFintheablationgroup. HeartRhythm,Vol10,No9,September2013 attemptedtominimizethisbyusingdiagnosiscodesofCVAthatwereassociatedwiththeprimarydiagnosisonaninpatientadmission.Inourstudypopulations,AFablationpatientshaveacantlylowerriskofstrokecomparedtoAFpatientswhodonotundergoablationindependentofbaselinestrokerisk.Thelowerriskpersistsacrossallage-relatedstrataandisindependentoftheCHADS2riskscore.Theselong-termdatacoupledwiththeobservationthatrisksaresimilartopatientswithoutAFsuggestthatablationtreatmentfavorablyaffectsstrokeriskinAF.WolfPA,DawberTR,ThomasHEJr,KannelWB.Epidemiologicassessmentofchronicatrialbrillationandriskofstroke:theFraminghamstudy.Neurology1978;28:973WolfPA,AbbottRD,KannelWB.Atrialbrillationasanindependentriskfactorforstroke:theFraminghamStudy.Stroke1991;22:983SeetRC,FriedmanPA,RabinsteinAA.Prolongedrhythmmonitoringforthedetectionofoccultparoxysmalatrialbrillationinischemicstrokeofunknowncause.Circulation2011;124:477HealeyJS,ConnollySJ,GoldMR,etal.Subclinicalatrialbrillationandtheriskofstroke.NewEnglJMed2012;366:120GageBF,WatermanAD,ShannonW,BoechlerM,RichMW,RadfordMJ.Validationofclinicalclassicationschemesforpredictingstroke:resultsfromtheNationalRegistryofAtrialFibrillation.JAMA2001;285:2864CrandallMA,HorneBD,DayJD,etal.AtrialbrillationsignicantlyincreasestotalmortalityandstrokeriskbeyondthatconveyedbytheCHADS2riskfactors.PacingClinElectrophysiol2009;32:981BunchTJ,CrandallBG,WeissJP,etal.Patientstreatedwithcatheterablationforatrialbrillationhavelong-termratesofdeath,stroke,anddementiasimilartopatientswithoutatrialbrillation.JCardiovascElectrophysiol2011;22:ThemistoclakisS,CorradoA,MarchlinskiFE,etal.Theriskofthrombo-embolismandneedfororalanticoagulationaftersuccessfulatrialablation.JAmCollCardiol2010;55:735HusseinAA,SalibaWI,MartinDO,etal.Naturalhistoryandlong-termoutcomesofablatedatrialbrillation.CircArrhythmElectrophysiol2011;4:MullerH,NobleS,KellerPF,etal.Biatrialanatomicalreverseremodellingafterradiofrequencycatheterablationforatrialbrillation:evidencefromreal-timethree-dimensionalechocardiography.Europace2008;10:1073PuwanantS,VarrBC,ShresthaK,etal.RoleoftheCHADS2scoreintheevaluationofthromboembolicriskinpatientswithatrialbrillationundergoingtransesophagealechocardiographybeforepulmonaryveinisolation.JAmCollCardiol2009;54:2032AllessieM,AusmaJ,SchottenU.Electrical,contractileandstructuralremodelingduringatrialbrillation.CardiovascRes2002;54:230JahangirA,LeeV,FriedmanPA,etal.Long-termprogressionandoutcomeswithaginginpatientswithloneatrialbrillation:a30-yearfollow-upstudy.Circulation2007;115:3050DaccarettM,BadgerTJ,AkoumN,etal.Associationofleftatrialdetectedbydelayed-enhancementmagneticresonanceimagingandtheriskofstrokeinpatientswithatrialbrillation.JAmCollCardiol2011;57:BadgerTJ,OakesRS,DaccarettM,etal.Temporalleftatriallesionformationafterablationofatrialbrillation.HeartRhythm2009;6:161GibsonDN,DiBiaseL,MohantyP,etal.Stiffleftatrialsyndromeaftercatheterablationforatrialbrillation:clinicalcharacterization,prevalence,andpredictors.HeartRhythm2011;8:1364HaeuslerKG,KochL,HermJ,etal.3TeslaMRI-detectedbrainlesionsafterpulmonaryveinisolationforatrialbrillation:resultsoftheMACPAFstudy.JCardiovascElectrophysiol2013;24:14ChatapG,GiraudK,VincentJP.Atrialbrillationintheelderly:factsandmanagement.DrugsAging2002;19:819 BunchetalAFPatientswithLong-TermStrokeRates