心电图学ppt课件

Electrocardiography ArecordingoftheelectricalactivityoftheheartovertimeGoldstandardfordiagnosisofcardiacarrhythmiasHelpsdetectelectrolytedisturbances hyper hypokalemia AllowsfordetectionofconductionabnormalitiesScreeningtoolforischemicheartdiseaseduringstresstestsHelpfulwithnon cardiacdiseases e g pulmonaryembolismorhypothermia Electrocardiogram ECG EKG Isarecordingofelectricalactivityofheartconductedthruionsinbodytosurface Fig13 22a 13 60 ECGGraphPaperRunsatapaperspeedof25mm secEachsmallblockofECGpaperis1mm2Atapaperspeedof25mm s onesmallblockequals0 04sFivesmallblocksmakeup1largeblockwhichtranslatesinto0 20s 200msec Hence thereare5largeblockspersecondVoltage 1mm 0 1mVbetweeneachindividualblockvertically Normalconductionpathway SAnode atrialmuscle AVnode bundleofHis LeftandRightBundleBranches Ventricularmuscle RecordingoftheECG Leadsused LimbleadsareI II II Socalledbecauseatonetimesubjectshadtoliterallyplacearmsandlegsinbucketsofsaltwater Eachoftheleadsarebipolar i e itrequirestwosensorsontheskintomakealead Ifoneconnectsalinebetweentwosensors onehasavector Therewillbeapositiveendatoneelectrodeandnegativeattheother ThepositioningforleadsI II andIIIwerefirstgivenbyEinthoven FormthebasisofEinthoven striangle TypesofECGRecordings Bipolarleadsrecordvoltagebetweenelectrodesplacedonwrists legs rightlegisground LeadIrecordsbetweenrightarm leftarmLeadII rightarm leftlegLeadIII leftarm leftleg Fig13 23 13 61 Fig 13 22b 3distinctwavesareproducedduringcardiaccyclePwavecausedbyatrialdepolarizationQRScomplexcausedbyventriculardepolarizationTwaveresultsfromventricularrepolarization ECG Fig13 24 13 63 ElementsoftheECG Pwave Depolarizationofbothatria RelationshipbetweenPandQRShelpsdistinguishvariouscardiacarrhythmiasShapeanddurationofPmayindicateatrialenlargementPRinterval fromonsetofPwavetoonsetofQRSNormalduration 0 12 2 0sec 120 200ms 3 4horizontalboxes Representsatriatoventricularconductiontime throughHisbundle ProlongedPRintervalmayindicatea1stdegreeheartblockQRScomplex VentriculardepolarizationLargerthanPwavebecauseofgreatermusclemassofventriclesNormalduration 0 08 0 12secondsItsduration amplitude andmorphologyareusefulindiagnosingcardiacarrhythmias ventricularhypertrophy MI electrolytederangement etc Qwavegreaterthan1 3theheightoftheRwave greaterthan0 04secareabnormalandmayrepresentMI STsegment ConnectstheQRScomplexandTwaveDurationof0 08 0 12sec 80 120msecTwave RepresentsrepolarizationorrecoveryofventriclesIntervalfrombeginningofQRStoapexofTisreferredtoastheabsoluterefractoryperiodQTIntervalMeasuredfrombeginningofQRStotheendoftheTwaveNormalQTisusuallyabout0 40secQTintervalvariesbasedonheartrate Fig 13 24b Fig 13 24c Fig 13 24d ElementsoftheECG PwaveDepolarizationofbothatria RelationshipbetweenPandQRShelpsdistinguishvariouscardiacarrhythmiasShapeanddurationofPmayindicateatrialenlargement QRScomplex RepresentsventriculardepolarizationLargerthanPwavebecauseofgreatermusclemassofventriclesNormalduration 0 08 0 12secondsItsduration amplitude andmorphologyareusefulindiagnosingcardiacarrhythmias ventricularhypertrophy MI electrolytederangement etc Qwavegreaterthan1 3theheightoftheRwave greaterthan0 04secareabnormalandmayrepresentMI PRinterval FromonsetofPwavetoonsetofQRSNormalduration 0 12 2 0sec 120 200ms 3 4horizontalboxes Representsatriatoventricularconductiontime throughHisbundle ProlongedPRintervalmayindicatea1stdegreeheartblock Fig 13 24g Twave RepresentsrepolarizationorrecoveryofventriclesIntervalfrombeginningofQRStoapexofTisreferredtoastheabsoluterefractoryperiod STsegment ConnectstheQRScomplexandTwaveDurationof0 08 0 12sec 80 120msecQTIntervalMeasuredfrombeginningofQRStotheendoftheTwaveNormalQTisusuallyabout0 40secQTintervalvariesbasedonheartrate IschemicHeartDisease IsmostcommonlyduetoatherosclerosisincoronaryarteriesIschemiaoccurswhenbloodsupplytotissueisdeficientCausesincreasedlacticacidfromanaerobicmetabolismOftenaccompaniedbyanginapectoris chestpain 13 78 ClickheretoplayMyocardialInfarctionRealMediaMovie IschemicHeartDisease DetectablebychangesinS TsegmentofECGMyocardialinfarction MI isaheartattackDiagnosedbyhighlevelsofcreatinephosphate CPK lactatedehydrogenase LDH Fig13 34 13 79 ArrhythmiasDetectedonECG ArrhythmiasareabnormalheartrhythmsHeartrate100 ministachycardia Fig13 35 13 80 ArrhythmiasDetectedonECGcontinued Influttercontractionratescanbe200 300 minInfibrillationcontractionofmyocardialcellsisuncoordinated pumpingineffectiveVentricularfibrillationislife threateningElectricaldefibrillationresynchronizesheartbydepolarizingallcellsatsametime Fig13 35 13 81 AVnodeblockoccurwhennodeisdamagedFirst degreeAVnodeblockiswhenconductionthroughAVnode 0 2secCauseslongP RintervalSecond degreeAVnodeblockiswhenonly1outof2 4atrialAPscanpasstoventriclesCausesPwaveswithnoQRSInthird degreeorcompleteAVnodeblocknoatrialactivitypassestoventriclesVentriclesdrivenslowlybybundleofHisorPurkinjes ArrhythmiasDetectedonECGcontinued 13 82 AVnodeblockoccurswhennodeisdamagedFirst degreeAVnodeblockiswhenconductionthruAVnode 0 2secCauseslongP Rinterval ArrhythmiasDetectedonECGcontinued Fig13 36 13 83 Second degreeAVnodeblockiswhenonly1outof2 4atrialAPscanpasstoventriclesCausesPwaveswithnoQRS ArrhythmiasDetectedonECGcontinued Fig13 36 13 84 Inthird degreeorcompleteAVnodeblock noatrialactivitypassestoventriclesVentriclesaredrivenslowlybybundleofHisorPurkinjes ArrhythmiasDetectedonECGcontinued Fig13 36 13 85 RepresentationincultureInTVmedicaldramas anisoelectricECG nocardiacelectric