Methodological ECG Interpretation€¦ · Methodological ECG Interpretation The ECG must always be...

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POCKETGUIDETO

ECGINTERPRETATION

DrArazRawshani,MD,PhD

UniversityofGothenburg

2017

P

P

R

QS

TU

P-wave duration

PR interval

QRS duration

J point

J 60 point

ST segment

TP intervalST-T segment


MethodologicalECGInterpretationTheECGmustalwaysbeinterpretedsystematically.Failuretoperformasystematicinterpretationof

theECGmaybedetrimental.Theinterpretationalgorithmpresentedbelowiseasytofollowandit

canbecarriedoutbyanyone.ThereaderwillgraduallynoticethatECGinterpretationismarkedly

facilitatedbyusinganalgorithm,asitminimizestheriskofmissingimportantabnormalitiesandalso

speedsuptheinterpretation.

1.Rhythm

ASSESSMENTS EVALUATION

Assessventricular(RRintervals)

andatrial(PPintervals)rateand

rhythm.

♥Isventricularrhythmregular?

Whatistheventricularrate

(beats/min)?

♥Isatrialrhythmregular?What

istheatrialrate(beats/min)?

♥P-wavesshouldprecedeevery

QRScomplexandtheP-wave

shouldbepositiveinleadII.

♥Sinusrhythm(whichisthenormalrhythm)hasthe

followingcharacteristics:(1)heartrate50–100beatsper

minute;(2)P-waveprecedeseveryQRScomplex;(3)theP-

waveispositiveinleadIIand(4)thePRintervalisconstant.

♥Causesofbradycardia:sinusbradycardia,sinoatrialblock,

sinoatrialarrest/inhibition,second-degreeAVblock,third-

degreeAVblock.Notethatescaperhythmsmayariseduring

bradycardia.Alsonotethatbradycardiaduetodysfunctionin

thesinoatrialnodeisreferredtoassinusnodedysfunction

(SND).IfapersonwithECGsignsofSNDissymptomatic,the

conditionisclassifiedassicksinussyndrome(SSS).

♥Causesoftachycardia(tachyarrhythmia)withnarrowQRS

complexes(QRSduration<0,12s):sinustachycardia,

inappropriatesinustachycardia,sinoatrialre-entry

tachycardia,atrialfibrillation,atrialflutter,atrialtachycardia,

multifocalatrialtachycardia,AVNRT,AVRT(pre-excitation,

WPW).Notethatnarrowcomplextachyarrhythmiararely

causescirculatorycompromiseorcollapse.

♥Causesoftachycardia(tachyarrhythmia)withwideQRS

complexes(QRSduration≥0,12s):ventriculartachycardiais

themostcommoncauseanditispotentiallylife-threatening.

Notethat10%ofwidecomplextachycardiasactuallyoriginate

fromtheatriabuttheQRScomplexesbecomewidedueto

abnormalventriculardepolarization(e.gsinustachycardia

withsimultaneousleftbundlebranchblock).

2.P-waveandPRinterval


♥P-wavealwayspositiveinlead

II(actuallyalwayspositiveinleads

II,IIIandaVF).

♥P-wavedurationshouldbe

<0,12s(allleads).

♥P-wavemustbepositiveinleadII,otherwisetherhythm

cannotbesinusrhythm.

♥P-wavemaybebiphasic(diphasic)inV1(thenegative

deflectionshouldbe<1mm).Itmayhaveaprominent

secondhumpintheinferiorlimbleads(particularlyleadII).


♥P-waveamplitudeshouldbe

≤2,5mm(allleads).PRinterval

mustbe0,12–0,22s(allleads).

♥Pmitrale:increasedP-waveduration,enhancedsecond

humpinleadIIandenhancednegativedeflectioninV1.

♥Ppulmonale:increasedP-waveamplitudesinleadIIand

V1.

♥IfP-wavenotclearlyvisible:lookforretrograde(inverted)

P-waves,whichcanbelocatedanywherebetweentheJpoint

andtheterminalpartoftheT-wave.

♥PRinterval>0,22s:first-degreeAVblock.

♥PRinterval<0,12s:Pre-excitation(WPWsyndrome).

♥Second-degreeAV-blockMobitztypeI(Wenckebach

block):repeatedcyclesofgraduallyincreasingPRinterval

untilanatrialimpulse(P-wave)isblockedinthe

atrioventricularnodeandtheQRScomplexdoesnotappear.

♥Second-degreeAV-blockMobitztypeII:intermittently

blockedatrialimpulses(noQRSseenafterP)butwith

constantPRinterval.

♥Third-degreeAV-block:Allatrialimpulses(P-waves)are

blockedbytheatrioventricularnode.Anescaperhythm

arises(cardiacarrestensuesotherwise),whichmayhave

narroworwideQRScomplexes,dependingonitsorigin.

ThereisnorelationbetweenP-wavesandtheescape

rhythm'sQRScomplexes,andatrialrhythmistypicallyfaster

thantheescaperhythm(bothrhythmsaretypicallyregular).

3.QRScomplex


♥QRSdurationmustbe<0,12s

(normally0,07-0,10s).

♥Theremustbeatleastone

limbleadwithR-waveamplitude

>5mmandatleastonechest

(precordial)leadwithR-wave

amplitude>10mm;otherwise

thereislowvoltage.

♥Highvoltageexistsifthe

amplitudesaretoohigh,i.eifthe

followingconditionissatisfied:S-

waveV1orV2+R-waveV5>35

mm.

♥LookforpathologicalQ-waves.

PathologicalQ-wavesare≥0,03s

and/oramplitude≥25%ofR-wave

amplitudeinsamelead,inatleast

2anatomicallycontiguousleads.

♥IstheR-waveprogressionin

thechestleads(V1–V6)normal?

♥WideQRScomplex(QRSduration≥0.12s):Leftbundle

branchblock.Rightbundlebranchblock.Nonspecific

intraventricularconductiondisturbance.Hyperkalemia.Class

Iantiarrhythmicdrugs.Tricyclicantidepressants.Ventricular

rhythmsandventricularextrasystoles(premature

complexes).Artificialpacemakerwhichstimulatesinthe

ventricle.Aberrantconduction(abberancy).Pre-excitation

(Wolff-Parkinson-Whitesyndrome).

♥ShortQRSduration:noclinicalrelevance.

♥Highvoltage:Hypertrophy(anylead).Leftbundlebranch

block(leadsV5,V6,I,aVL).Rightbundlebranchblock(V1–

V3).Normalvariantinyounger,well-trainedandslender

individuals.

♥Lowvoltage:Normalvariant.Misplacedleads.

Cardiomyopathy.Chronicobstructivepulmonarydisease.

Perimyocarditis.Hypothyreosis(typicallyaccompaniedby

bradycardia).Pneumothorax.Extensivemyocardialinfarction.

Obesity.Pericardialeffusion.Pleuraleffusion.Amyloidosis.

♥PathologicalQ-waves:Myocardialinfarction.Left-sided

pneumothorax.Dextrocadia.Perimyocarditis.

Cardiomyopathy.Amyloidosis.Bundlebranchblocks.Anterior


♥Istheelectricalaxisnormal?

Electricalaxisisassessedinlimb

leadsandshouldbebetween–30°

to90°.

fascicularblock.Pre-excitation.Ventricularhypertrophy.

Acutecorpulmonale.Myxoma.

♥FragmentedQRScomplexesindicatesmyocardialscarring

(mostlyduetoinfarction).

♥AbnormalR-waveprogression:Myocardialinfarction.

Rightventricularhypertrophy(reversedR-waveprogression).

Leftventricularhypertrophy(amplifiedR-waveprogression).

Cardiomyopathy.Chroniccorpulmonale.Leftbundlebranch

block.Pre-excitation.

♥DominantR-waveinV1/V2:Misplacedchestelectrodes.

Normalvariant.Situsinversus.Posterolateral

infarction/ischemia(ifpatientexperienceschestdiscomfort).

Rightventricularhypertrophy.Hypertrophiccardiomyopathy.

Rightbundlebranchblock.Pre-excitation.

♥Rightaxisdeviation:Normalinnewborns.Rightventricular

hypertrophy.Acutecorpulmonale(pulmonaryembolism).

Chroniccorpulmonale(COPD,pulmonaryhypertension,

pulmonaryvalvestenosis).Lateralventricularinfarction.Pre-

excitation.Switchedarmelectrodes(negativePandQRS-Tin

leadI).Situsinversus.Leftposteriorfascicularblockis

diagnosedwhentheaxisisbetween90°and180°withrS

complexinIandaVLaswellasqRcomplexinIIIandaVF

(withQRSduration<0.12seconds),providedthatother

causesofrightaxisdeviationhavebeenexcluded.

♥Leftaxisdeviation:Leftbundlebranchblock.Left

ventricularhypertrophy.Inferiorinfarction.Pre-excitation.

Leftanteriorfascicularblockisdiagnosediftheaxisis

between-45°and90°withqR-complexinaVLandQRS

durationis0,12s,providedthatothercausesofleftaxis

deviationhavebeenexcluded.

♥Extremeaxisdeviation:Rarelyseen.Probablymisplaced

electrodes.IftherhythmiswideQRScomplextachycardia,

thenthecauseisprobablyventriculartachycardia.

4.STsegment


♥TheST-segmentshouldbeflat

andisoelectric(inlevelwiththe

baseline).Itmaybeslightly

upslopingatthetransitionwith

theT-wave.

• ♥STsegmentdeviation

(elevationanddepression)

ismeasuredintheJpoint.

♥BenignSTsegmentelevationisverycommoninthe

population,particularlyintheprecordialleads(V2–V6).Upto

90%(insomeage-ranges)ofhealthymenandwomendisplay

concaveST-segmentelevationsinV2–V6(thisiscalled

male/femalepattern).ST-segmentelevationswhicharenot

benignnorduetoischemiaarerathercommon(listed

below).

• ♥ST-segmentdepressionisuncommonamonghealthy

individuals.ST-segmentdepressionisparticularlysuspicious

inthechestleads.Guidelinesrecommendthat<0.5mmST-

segmentdepressionbeacceptedinallleads.


• ♥CausesofST-segmentelevation:Ischemia.STsegment

elevationmyocardialinfarction(STEMI/STE-AKS).Prinzmetal's

angina(coronaryvasospasm).Male/femalepattern.Early

repolarization.Perimyocarditis.Leftbundlebranchblock.

Nonspecificintraventricularconductiondisturbance.Left

ventricularhypertrophy.Brugadasyndrome.Takotsubo

cardiomyopathy.Hyperkalemia.Postcardioversion.

Pulmonaryembolism.Pre-excitation.Aorticdissection

engagingthecoronaryarteries.Leftventricularaneurysm.

• ♥CausesofST-segmentdepression:Ischemia.Non-ST

segmentelevationmyocadialinfarction(NSTEMI/NSTE-AKS).

PhysiologicalST-segmentdepression.Hyperventilation.

Hypokalemia.Highsympathethictone.Digoxin.Leftbundle

branchblock.Rightbundlebranchblock.Pre-excitation.Left

ventricularhypertrophy.Rightventricularhypertrophy.Heart

failure.Tachycardia.

• ♥Causesofwaves/deflectionsintheJpoint(Jwave

syndromes):Brugadasyndrome.Earlyrepolarization.

5.T-wave


• ♥ShouldbeconcordantwiththeQRScomplex.Shouldbepositive

inmostleads.

• ♥T-waveprogressionshouldbe

normalinchestleads.

• ♥Inlimbleadstheamplitudeis

highestinleadII,andinthechest

leadstheamplitudeishighestin

V2–V3.

♥Normalvariants:Anisolated(single)T-waveinversionis

acceptedinleadV1andleadIII.InsomeinstancestheT-wave

inversionsfromchildhoodmaypersistinV1–V3(V4),whichis

calledpersistentjuvenileT-wavepattern.Rarely,allT-waves

remaininverted,whichiscalledglobalidiopathicT-wave

inversion(V1–V6).

• ♥T-waveinversionwithoutsimultaneousST-segment

deviation:Thisisnotasignofongoingischemia,butmaybe

post-ischemic.Onetypeofpost-ischemicT-waveinversionis

especiallyacute,namelyWellen'ssyndrome(characterizedby

deepT-waveinversionsinV1–V6inpatientwithrecent

episodesofchestpain).Cerebrovascularinsult(bleeding).

Pulmonaryembolism.Perimyocarditis(afternormalizationof

theST-segmentelevation,T-wavesbecomeinvertedin

perimyocarditis).Cardiomyopathy.

• ♥T-waveinversionwithsimultaneousST-segment

deviation:acute(ongoing)myocardialischaemia.

• ♥HighT-waves:Normalvariant.Earlyrepolarization.

Hyperkalemia.Leftventricularhypertrophy.Leftbundle

branchblock.Occasionallyperimyocarditis.High(hyperacute)

T-wavesmaybeseenintheveryearlyphaseofSTEMI.


6.QTcintervalandU-wave


♥QTcdurationmen≤0,45s.

♥QTcdurationwomen≤0,46s.

♥ProlongedQTcdurationmay

causemalignantarrhythmias

(torsadedepointes,whichisa

typeofventriculartachycardia).

♥ShortenedQTcduration(≤0.32

s)israre,butmayalsocause

malignantventricular

arrhythmias.

♥TheU-waveisseen

occasionally,especiallyinwell-

trainedindividuals,andduring

lowheartrate.ItislargestinV3–

V4.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.Acompletelistof

drugscausingQTprolongationcanbefoundhere.

• ♥CongenitalQTprolongation:geneticdiseaseofwhich

thereareapproximately15variants.

• ♥ShortQTcsyndrome(≤0,32s):causedbyhyperkalcemia

anddigoxintreatment.Maycausemalignantventricular

arrhythmia.

• ♥NegativeU-wave:highspecificityforheartdisease

(includingischemia).

•

7.ComparewithearlierECGtracings

ItisfundamentaltocomparethecurrentECGwithpreviousrecordings.Allchangesareofinterest

andmayindicatepathology.

8.ClinicalcontextECGchangesshouldbeputintoaclinicalcontext.Forexample,ST-segmentelevationsarecommon

inthepopulationandshouldnotraisesuspicionofmyocardialischemiaifthepatientdonothave

symptomssuggestiveofischemia.

Theguidecontinuesonthenextpage.


Thecardiacconductionsystem

Waves,intervalsanddurationsontheECG


Thewallsoftheleftventricleandtheleadsthatview

thesewalls

TheECGleads


P-wavechanges


STsegmentdepressions


STsegmentelevations


T-wavechanges


Electricalaxisoftheheart

Asevidentfromthefigureabove,thenormalheartaxisisbetween–30°and90°.Iftheaxisismore

positivethan90°itisreferredtoasrightaxisdeviation.Iftheaxisismorenegativethan–30°itis

referredtoasleftaxisdeviation.Theaxisiscalculated(tothenearestdegree)bytheECGmachine.

TheaxiscanalsobeapproximatedmanuallybyjudgingthenetdirectionoftheQRScomplexinleads

IandII.Thefollowingrulesapply:

• Normalaxis:NetpositiveQRScomplexinleadsIandII.

• Rightaxisdeviation:NetnegativeQRScomplexinleadIbutpositiveinleadII.

• Leftaxisdeviation:NetpositiveQRScomplexinleadIbutnegativeinleadII.

• Extremeaxisdeviation(–90°to180°):NetnegativeQRScomplexinleadsIandII.


Pro-arrhythmicECGchangesduringsinusrhythm


AssessmentofRPintervalfortachyarrhythmias


Diagnosisandmanagementoftachyarrhythmiaswith

narrowQRScomplex


Diagnosisandmanagementoftachyarrhythmiaswith

wideQRScomplex


Intraventricularconductiondefects


Hypertrophyanddilatation


Classificationofacutecoronarysyndromes(ACS)


Criteriaforacutemyocardialinfarction(AMI)

STE-ACS(STEMI)–STelevationacutemyocardialinfarction

CriteriaforSTEMINewSTsegmentelevationsinatleasttwoanatomicallycontiguousleads:

• Menage≥40years:≥2mminV2-V3and≥1mminallotherleads.

• Menage<40years:≥2,5mminV2-V3and≥1mminallotherleads.

• Women(anyage):≥1,5mminV2-V3and≥1mminallotherleads.

• Men&womenV4RandV3R:≥0,5mm,exceptfrommen<30yearsinwhomthecriteriais≥1mm.

• Men&womenV7-V9:≥0,5mm.

NSTE-ACS(NSTE-ACS)–NonSTelevationacutemyocardial

infarction:NSTEMIandunstableangina

• NewhorizontalordownslopingSTsegmentdepressions≥0,5mminatleasttwoanatomically

contiguousleads.

• Twaveinversion≥1mminatleasttwoanatomicallycontiguousleads.Theseleadsmusthave

evidentR-waves,orR-waveslargerthanS-waves.

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