Methodological ECG Interpretation | Learn ECG Interpretation Online Methodological ECG Interpretation The ECG must always be interpreted systematically. Failure to perform

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    ECGWAVES.COM

    POCKETGUIDETO

    ECGINTERPRETATION

    DrArazRawshani,MD,PhDUniversityofGothenburg2017

    PP

    R R

    Q QS S

    TU

    P-wave duration

    PR interval

    QRS duration

    J pointJ 60 point

    ST segment

    TP intervalST-T segment

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    MethodologicalECGInterpretationTheECGmustalwaysbeinterpretedsystematically.FailuretoperformasystematicinterpretationoftheECGmaybedetrimental.Theinterpretationalgorithmpresentedbelowiseasytofollowanditcanbecarriedoutbyanyone.ThereaderwillgraduallynoticethatECGinterpretationismarkedlyfacilitatedbyusinganalgorithm,asitminimizestheriskofmissingimportantabnormalitiesandalsospeedsuptheinterpretation.

    1.RhythmASSESSMENTS EVALUATIONAssessventricular(RRintervals)andatrial(PPintervals)rateandrhythm.Isventricularrhythmregular?Whatistheventricularrate(beats/min)?Isatrialrhythmregular?Whatistheatrialrate(beats/min)?P-wavesshouldprecedeeveryQRScomplexandtheP-waveshouldbepositiveinleadII.

    Sinusrhythm(whichisthenormalrhythm)hasthefollowingcharacteristics:(1)heartrate50100beatsperminute;(2)P-waveprecedeseveryQRScomplex;(3)theP-waveispositiveinleadIIand(4)thePRintervalisconstant.Causesofbradycardia:sinusbradycardia,sinoatrialblock,sinoatrialarrest/inhibition,second-degreeAVblock,third-degreeAVblock.Notethatescaperhythmsmayariseduringbradycardia.Alsonotethatbradycardiaduetodysfunctioninthesinoatrialnodeisreferredtoassinusnodedysfunction(SND).IfapersonwithECGsignsofSNDissymptomatic,theconditionisclassifiedassicksinussyndrome(SSS).Causesoftachycardia(tachyarrhythmia)withnarrowQRScomplexes(QRSduration

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    P-waveamplitudeshouldbe2,5mm(allleads).PRintervalmustbe0,120,22s(allleads).

    Pmitrale:increasedP-waveduration,enhancedsecondhumpinleadIIandenhancednegativedeflectioninV1.Ppulmonale:increasedP-waveamplitudesinleadIIandV1.IfP-wavenotclearlyvisible:lookforretrograde(inverted)P-waves,whichcanbelocatedanywherebetweentheJpointandtheterminalpartoftheT-wave.PRinterval>0,22s:first-degreeAVblock.PRinterval

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    Istheelectricalaxisnormal?Electricalaxisisassessedinlimbleadsandshouldbebetween30to90.

    fascicularblock.Pre-excitation.Ventricularhypertrophy.Acutecorpulmonale.Myxoma.FragmentedQRScomplexesindicatesmyocardialscarring(mostlyduetoinfarction).AbnormalR-waveprogression:Myocardialinfarction.Rightventricularhypertrophy(reversedR-waveprogression).Leftventricularhypertrophy(amplifiedR-waveprogression).Cardiomyopathy.Chroniccorpulmonale.Leftbundlebranchblock.Pre-excitation.DominantR-waveinV1/V2:Misplacedchestelectrodes.Normalvariant.Situsinversus.Posterolateralinfarction/ischemia(ifpatientexperienceschestdiscomfort).Rightventricularhypertrophy.Hypertrophiccardiomyopathy.Rightbundlebranchblock.Pre-excitation.Rightaxisdeviation:Normalinnewborns.Rightventricularhypertrophy.Acutecorpulmonale(pulmonaryembolism).Chroniccorpulmonale(COPD,pulmonaryhypertension,pulmonaryvalvestenosis).Lateralventricularinfarction.Pre-excitation.Switchedarmelectrodes(negativePandQRS-TinleadI).Situsinversus.Leftposteriorfascicularblockisdiagnosedwhentheaxisisbetween90and180withrScomplexinIandaVLaswellasqRcomplexinIIIandaVF(withQRSduration

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    CausesofST-segmentelevation:Ischemia.STsegmentelevationmyocardialinfarction(STEMI/STE-AKS).Prinzmetal'sangina(coronaryvasospasm).Male/femalepattern.Earlyrepolarization.Perimyocarditis.Leftbundlebranchblock.Nonspecificintraventricularconductiondisturbance.Leftventricularhypertrophy.Brugadasyndrome.Takotsubocardiomyopathy.Hyperkalemia.Postcardioversion.Pulmonaryembolism.Pre-excitation.Aorticdissectionengagingthecoronaryarteries.Leftventricularaneurysm.

    CausesofST-segmentdepression:Ischemia.Non-STsegmentelevationmyocadialinfarction(NSTEMI/NSTE-AKS).PhysiologicalST-segmentdepression.Hyperventilation.Hypokalemia.Highsympathethictone.Digoxin.Leftbundlebranchblock.Rightbundlebranchblock.Pre-excitation.Leftventricularhypertrophy.Rightventricularhypertrophy.Heartfailure.Tachycardia.

    Causesofwaves/deflectionsintheJpoint(Jwavesyndromes):Brugadasyndrome.Earlyrepolarization.

    5.T-waveASSESSMENTS EVALUATION

    ShouldbeconcordantwiththeQRScomplex.Shouldbepositiveinmostleads.

    T-waveprogressionshouldbenormalinchestleads.

    InlimbleadstheamplitudeishighestinleadII,andinthechestleadstheamplitudeishighestinV2V3.

    Normalvariants:Anisolated(single)T-waveinversionisacceptedinleadV1andleadIII.InsomeinstancestheT-waveinversionsfromchildhoodmaypersistinV1V3(V4),whichiscalledpersistentjuvenileT-wavepattern.Rarely,allT-wavesremaininverted,whichiscalledglobalidiopathicT-waveinversion(V1V6).

    T-waveinversionwithoutsimultaneousST-segmentdeviation:Thisisnotasignofongoingischemia,butmaybepost-ischemic.Onetypeofpost-ischemicT-waveinversionisespeciallyacute,namelyWellen'ssyndrome(characterizedbydeepT-waveinversionsinV1V6inpatientwithrecentepisodesofchestpain).Cerebrovascularinsult(bleeding).Pulmonaryembolism.Perimyocarditis(afternormalizationoftheST-segmentelevation,T-wavesbecomeinvertedinperimyocarditis).Cardiomyopathy.

    T-waveinversionwithsimultaneousST-segmentdeviation:acute(ongoing)myocardialischaemia.

    HighT-waves:Normalvariant.Earlyrepolarization.Hyperkalemia.Leftventricularhypertrophy.Leftbundlebranchblock.Occasionallyperimyocarditis.High(hyperacute)T-wavesmaybeseenintheveryearlyphaseofSTEMI.

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    6.QTcintervalandU-waveASSESSMENTS EVALUATIONQTcdurationmen0,45s.QTcdurationwomen0,46s.ProlongedQTcdurationmaycausemalignantarrhythmias(torsadedepointes,whichisatypeofventriculartachycardia).ShortenedQTcduration(0.32s)israre,butmayalsocausemalignantventriculararrhythmias.TheU-waveisseenoccasionally,especiallyinwell-trainedindividuals,andduringlowheartrate.ItislargestinV3V4.AmplitudeisonefourthofT-waveamplitude.

    AcquiredQTprolongation:antiarrhythmicdrugs(procainamide,disopyramide,amiodarone,sotalol),psychiatricmedications(tricyclicantidepressants,SSRI,lithiumetc);antibiotics(macrolides,kinolones,atovaquone,klorokine,amantadin,foscarnet,atazanavir);hypokalemia,hypocalcemia,hypomagnesemia;cerebrovascularinsult(bleeding);myocardialischemia;cardiomyopathy;bradycardia;hypothyroidism;hypothermia.AcompletelistofdrugscausingQTprolongationcanbefoundhere.

    CongenitalQTprolongation:geneticdiseaseofwhichthereareapproximately15variants.

    ShortQTcsyndrome(0,32s):causedbyhyperkalcemiaanddigoxintreatment.Maycausemalignantventriculararrhythmia.

    NegativeU-wave:highspecificityforheartdisease(includingischemia).

    7.ComparewithearlierECGtracingsItisfundamentaltocomparethecurrentECGwithpreviousrecordings.Allchangesareofinterestandmayindicatepathology.

    8.ClinicalcontextECGchangesshouldbeputintoaclinicalcontext.Forexample,ST-segmentelevationsarecommoninthepopulationandshouldnotraisesuspicionofmyocardialischemiaifthepatientdonothavesymptomssuggestiveofischemia.

    Theguidecontinuesonthenextpage.

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    Thecardiacconductionsystem

    Waves,intervalsanddurationsontheECG

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    Thewallsoftheleftventricleandtheleadsthatviewthesewalls

    TheECGleads

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    P-wavechanges

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    STsegmentdepressions

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    STsegmentelevations

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    T-wavechanges

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    Electricalaxisoftheheart

    Asevidentfromthefigureabove,thenormalheartaxisisbetween30and90.Iftheaxisismorepositivethan90itisreferredtoasrightaxisdeviation.Iftheaxisismorenegativethan30itisreferredtoasleftaxisdeviation.Theaxisiscalculated(tothenearestdegree)bytheECGmachine.TheaxiscanalsobeapproximatedmanuallybyjudgingthenetdirectionoftheQRScomplexinleadsIandII.Thefollowingrulesapply:

    Normalaxis:NetpositiveQRScomplexinleadsIandII. Rightaxisdeviation:NetnegativeQRScomplexinleadIbutpositiveinleadII. Leftaxisdeviation:NetpositiveQRScomplexinleadIbutnegativeinleadII. Extremeaxisdeviation(90to180):NetnegativeQRScomplexinleadsIandII.

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    Pro-arrhythmicECGchangesduringsinusrhythm

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    AssessmentofRPintervalfortachyarrhythmias

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    DiagnosisandmanagementoftachyarrhythmiaswithnarrowQRScomplex

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    DiagnosisandmanagementoftachyarrhythmiaswithwideQRScomplex

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    Intraventricularconductiondefects

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    Hypertrophyanddilatation

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    Classificationofacutecoronarysyndromes(ACS)

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    Criteriaforacutemyocardialinfarction(AMI)

    STE-ACS(STEMI)STelevationacutemyocardialinfarction

    CriteriaforSTEMINewSTsegmentelevationsinatleasttwoanatomicallycontiguousleads:

    Menage40years:2mminV2-V3and1mminallotherleads.

    Menage