Objective:Toinvestigatetheinfluenceofdifferentrightventricular(RV)pacingsitesonQRSwidth,andtoprovideapotentialreferencesiteforpermanentrightventricularpacinginpatientsimplantedwithpermanentpacemakers.PacingatthesitewiththeshortestQRSdurationmayreducethedeleteriouseffectsofRVpacingonLVfunction,andthushavingbeneficialeffectsonpatient’soutcome.Methods:AllconsecutivepatientswhowereplannedtohavepermanentpacemakerimplantationforaClassIorIIaindicationatourdepartmentfromOctober2010toJuly2012werescreenedfortheparticipationinthisprospective,singlecenter,non-randomizedstudy.ThebaselinesurfaceECGwasanalyzedforQRSwidthandmorphology,respectively.DuringtheimplantationprocedurepatientsweretransientlypacedatdifferentRVlocations(rightventricularapex,rightventricularinflowtract[RVIT],midseptum,highseptumandrightventricularoutflowtract[RVOT])beforetheleadwasplacedatitsfinalposition.Duringpacingatthedifferentpositionsthesurface12-leadsECGwasrecorded.BasedonthesurfaceofECGQRSdurationandmorphologyofthedifferentrightventricularpacingsiteswereanalyzedandcomparedwithbaselineandtoeachother.Results:Atotalof216patients(39%female,meanage69±13years,higherdegreeAVblock30.5%)wasenrolledinthestudy.PacedQRSdurationwassignificantlydifferentbetweenallrightventricularpacingsitescomparedwiththebaselineECG(baseline:106ms±21ms;meanpaced:158ms±16ms;p<0.001).RVApacingshowedthewidestQRS(168ms±16ms).QRSdurationwithRVITpacingwas166ms±15ms,andthatwithRVOTpacingwas165ms±15ms,respectively.QRSdurationwasnotsignificantlydifferentbetweenthesethreepositions.Mid-septalpacingshowedthenarrowestQRS(139ms±19ms)comparedtoallotherpacingsites(p<0.001).Pacingatthehigh-septumshowedabroaderQRS(153ms±14ms)thanthatpacingatthemid-septum.Comparedtootherrightventricularpacingsites
