Basic Electrocardiography: Normal and Abnormal ECG Patterns

180 Pages·2007·6.05 MB·English

by  A. Bayes de Luna(auth.)

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Basic
Electrocardiography
NORMAL AND ABNORMAL
ECG PATTERNS
i
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Basic
Electrocardiography
NORMAL AND ABNORMAL
ECG PATTERNS
A. Bayés de Luna,MD, FESC, FACC
ProfessorofMedicine,UniversidadAutonomaBarcelona
DirectorofInstitutCataladeCardiologia
HospitalSantaCreuISantPau
St.AntoniM.Claret167
DirectorCardiacDepartment–H.Quiron.Barcelona
ES-08025
Barcelona
Spain
iii
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(cid:2)
C 2007A.BayésdeLuna
PublishedbyBlackwellPublishing
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Firstpublished2007
1 2007
ISBN:978-1-4051-7570-8
LibraryofCongressCataloging-in-PublicationData
BayesdeLuna,Antonio.
Basicelectrocardiography:normalandabnormalECGpatterns/AntoniBayesdeLuna.
p.;cm.
Includesbibliographicalreferencesandindex.
ISBN978-1-4051-7570-8
1.Electrocardiography. 2.Heart–Diseases–Diagnosis. I.Title.
[DNLM:1.Electrocardiography. 2.Electrocardiography–methods.
WG140B357b2007]
RC683.5.E5B3242007
616.1(cid:3)207547–dc22
2007006646
AcataloguerecordforthistitleisavailablefromtheBritishLibrary
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Contents
Foreword,vii
1 Introduction,1
2 Usefulnessandlimitationsofelectrocardiography,4
3 Electrophysiologicalprinciples,6
TheoriginofECGmorphology,6
4 ECGmachines:howtoperformandinterpretECG,19
5 NormalECGcharacteristics,21
Heartrate,21
Rhythm,21
PRintervalandsegment,21
QTinterval,23
Pwave,24
QRScomplex,24
STsegmentandTwave,24
AssessmentoftheQRSelectricalaxisinthefrontalplane,26
Rotationsoftheheart,26
Electrocardiographicchangeswithage,30
6 Electrocardiographicdiagnosticcriteria,32
7 Atrialabnormalities,35
Rightatrialenlargement,35
Leftatrialenlargement,35
Biatrialenlargement,37
Interatrialblock,37
8 Ventricularenlargement,39
Rightventricularenlargement,40
Electrocardiographicsignsofrightacuteoverload,44
Leftventricularenlargement,44
Biventricularenlargement,48
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vi Contents
9 Ventricularblocks,50
Completerightbundlebranchblock(RBBB),53
Partialrightbundlebranchblock,55
Completeleftbundlebranchblock(LBBB),57
Partialleftbundlebranchblock,58
Zonal(divisional)leftventricularblock,58
Bifascicularblocks,59
Trifascicularblocks,60
10 Ventricularpre-excitation,61
WPW-typepre-excitation,61
ShortPRtypepre-excitation(Lown–Ganong–Levine
syndrome),67
11 Electrocardiographicpatternofischaemia,injury
andnecrosis,68
Anatomicintroduction,68
Electrophysiologicalintroduction,69
Electrocardiographicpatternofischaemia,73
Electrocardiographicpatternofinjury,80
Electrocardiographicpatternofnecrosis,97
12 Miscellaneous,117
ValueofECGinspecialconditions,117
ECGpatternofpoorprognosis,117
ECGofelectricalalternans,117
Self-assessment,121
References,165
Index,169
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Foreword
BasicElectrocardiography:NormalandAbnormalECGPatternsisnotanadditional
regulartextbookonelectrocardiography.ProfessorAntoniBaye´sdeLuna,the
authorofthepresenttextbookisaworld-widerenownedelectrocardiographer
and clinical cardiologist who has contributed to our knowledge and under-
standingofelectrocardiologyovertheyears.Inthepresenttextbook,heshares
withushisvastexperienceandknowledge,summarisingthetraditionalcon-
ceptsofelectrocardiographyandvectrocardiographycombinedwithcurrent
updatesonthemostrecentdevelopmentscorrelatingelectrocardiographicpat-
terns with magnetic resonance imaging. This textbook is of particular value
totheAmericanphysiciansandhealthcareproviders,asitexposesthereader
to the Mexican, Argentinean and European schools of electrocardiography,
whichsomeoftheearliertextbookshavetendedtooverlook.
Thepresenttextbookprovidesaconcisesummaryoftheclassicalandmod-
ernconceptsofelectrocardiologyandprovides22casescoveringawidespec-
trum of normal variations and abnormal electrocardiographic findings. In
thesecasesDr.Baye´sdeLunaexplainshisapproachforinterpretingtheelec-
trocardiogramandintegratingitwiththeclinicalfindings.
In conclusion, this textbook is an asset for every cardiologist, internist,
primary care physician, as well as medical students and other healthcare
providersinterestedinbroadeningtheirskillsinelectrocardiography.
YochaiBirnbaum,MD
EdwardD.andSallyM.FutchProfessorofMedicine
BiochemistryandMolecularBiology
MedicalDirector,CardiacIntensiveCareUnit
MedicalDirector,theHeartStation
TheDivisionofCardiology
TheUniversityofTexasMedicalBranch
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CHAPTER 1
Introduction
Theelectrocardiogram(ECG),introducedintoclinicalpracticemorethan100
yearsagobyEinthoven,constitutesalinealrecordingoftheheart’selectrical
activity that occurs successively over time. An atrial depolarisation wave (P
wave), a ventricular depolarisation wave (QRS complex) and a ventricular
repolarisationwave(Twave)aresuccessivelyrecordedforeachcardiaccycle
(Figures 1A–C). As these different waves are recorded from different sites
(leads)themorphologyvaries(Figure2).Nevertheless,thesequenceisalways
P–QRS–T.AnECGcurverecordedfromanelectrodefacingtheleftventricleis
showninFigure1D.Dependingontheheartrate,theintervalbetweenwaves
ofonecycleandanotherisvariable.
Other different forms of recording cardiac activity (vectorcardiography,
bodymapping,etc.)exist[1].Vectorcardiography(VCG)representselectrical
activitybydifferentloopsoriginatingfromtheunionoftheheadsofmultiple
vectorsofatrialdepolarisation(Ploop),ventriculardepolarisation(QRSloop),
andventricularrepolarisation(Tloop).AclosecorrelationexistsbetweenVCG
loopsandtheECGcurve.Therefore,onemaydeductECGmorphologyonthe
basis of the morphology of VCG loop and vice versa. This is due to loop–
hemifieldcorrelationtheory(seep.10).Accordingtothiscorrelation(Figures
16,18and21),themorphologyofdifferentwaves(P,QRSandT)recordedfrom
differentsides(leads)varies(Figure2).Astheheartisathree-dimensionalor-
gan,projectionoftheloopswiththeirmaximumvectorsintwoplanes,frontal
and horizontal, on the positive and the negative hemifield∗ of each lead is
required to ascertain exactly the loop’s location and allow deducting ECG
morphology(Figures3and4).ThemorphologyofECGdependsnotonlyon
the maximum vector of a given loop butalso onitsrotation (Figure 4).This
representstheimportanceofconsideringtheloopandnotonlyitsmaximum
vectortoexplaintheECGmorphology.
∗Thepositiveandthenegativehemifieldofeachleadareobtainedbydrawinglines
perpendiculartoeachlead,passingthroughthecentreoftheheart.Thepositivehemifield
islocatedintheareaofpositivepartofthelead,andthenegativehemifieldinthenegative
part.InFigure4thepositivehemifieldisthearealocatedbetween−90◦and+90◦passing
through0◦,andthepositivehemifieldofleadVFisthearealocatedbetween0◦and180◦
passingthrough+90◦.Theotherpartoftheelectricalfieldcorrespondstothenegative
hemifieldofeachlead(seep.10).
1
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2 Chapter1
A B
1
1 3
+1
3
+1 2
2
2
VF 1 3
C D
+1 P T
+1
QRS
VF VF
Figure1 Three-dimensionalperspectiveofthePloop(A),QRSloopwithitsthreerepresentative
vectors(B)andTloop(C),andtheirprojectiononthefrontalplanewiththecorrelationloop–ECG
morphology.(D)GlobalcorrelationbetweentheP,QRSandTloopsandECGmorphologyonthe
frontalplanerecordedinaleadfacingtheleftventriclefreewall(leadI).
A
rS RS Rs QS R R slurred
rSr´ rSR´ rsr’s´ Qr QR Q slurred R
qR qRs qRS qrS Q slurred
B
Flat Peaked Bimodal
Positive
Negative
Diphasic
+ − − + + − − + + − − + + − − +
Isodiphasic
Figure2 ThemostfrequentQRScomplexmorphologies(A),PandTwavesmorphologies(B).
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Introduction 3
A B C D
FP FP FP FP
I I
V
6
HP HP HP HP
V V
1 2
Figure3 Aloopwithitsmaximumvectordirecteddownwards,totheleftandforwards(A)and
anotherwithitsmaximumvectordirecteddownwards,totheleftandbackwards(B)havethesame
projectionsonthefrontalplane(FP)butdifferentprojectionsonthehorizontalplane(HP).Onthe
otherhand,aloopwiththemaximumvectordirectedupwards,totheleftandforwards(C)and
anotherwiththemaximumvectordirecteddownwards,totheleftandforwards(D)producethe
sameprojectionontheHP,butdifferentprojectionsontheFP.
A B C
A B
B
I I
A
B A
VF VF VF
Figure4 Ifthemaximumvectorofaloopfallsinthelimitofpositiveandnegativehemifieldsofa
certainlead,anisodiphasicdeflectionisrecorded.However,accordingtothedirectionofloop
rotationtheQRScomplexmaybepositive–negativeornegative–positive(seeexamplesforleads
VFandIinthecaseofmaximumvectordirectedto0◦(B)and+90◦(C)).Theloopwithmaximum
vectorat45◦(A)alwaysfailsinthepositivehemifieldofIandVF,independentlyofthesenseof
rotation.
VCGisrarelyusedincurrentclinicalpractice;however,itishighlyusefulin
understandingECGmorphologiesandinteachingelectrocardiography.Later
inthisbookwewillexplaininmoredetailhowtheloopsoriginateandhow
theirprojectioninfrontalandhorizontalplanesexplainstheECGmorpholo-
giesindifferentleads.
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CHAPTER 2
Usefulness and limitations
of electrocardiography
ECGisthetechniqueofchoiceinthestudyofpatientswithchestpain,syncope,
palpitations and acute dyspnoea, and is crucial for the diagnosis of cardiac
arrhythmias, conduction disturbances, pre-excitation syndromes and chan-
nelopathies.Itisalsoveryimportantforassessingtheevolutionandresponse
totreatmentofalltypesofheartdiseasesandotherdiseases,anddifferentsit-
uationssuchaselectrolyticdisorders,drugadministration,athletes,surgical
evaluation,etc.Additionally,itisusefulforepidemiologicstudiesandscreen-
ing(check-up).
Despiteitsinvaluableusefulnessifusedcorrectly,electrocardiographymay
inducemistakesifoneexcessivelytrustsonanECGrecordingofnormalap-
pearance.Sometimes,bowingtothe‘magical’powerofECG,physicianscaring
forapatientwithchestpainofdoubtfuloriginmaystate:‘Let’shaveanECG
recording done so that we may solve the problem’. It must be remembered
thatahighpercentageofpatientswithcoronaryheartdisease,intheabsence
ofchestpain,showanormalECGrecordingandthateveninacutecoronary
syndromesECGisnormalorborderlineinapproximately5–10%ofcases,and
without symptoms especially in its early phase. Furthermore, ECG may be
normalmonthsoryearsafteramyocardialinfarction.Fromtheabove,itcan
beinferredthatanormalECGdoesnotimplyany‘lifeinsurance’asapatient
maydiefromcardiaccausesevenonthesamedayanormalrecordingistaken.
However,itisevidentthatintheabsenceofclinicalfindingsorfamilyhistory
ofsuddendeath,thepossibilityofthisoccurringis,infact,veryremote.
On the other hand, on occasions some subtle ECG abnormalities with no
evidence of heart disease may be observed. Clearly, in such cases one must
becautious,andbeforeconsideringthistobeanon-specificabnormality,is-
chaemicheartdisease,channelopathies(longQT,Brugada’ssyndrome,etc.)or
pre-excitationsyndromesshouldberuledout.Therefore,itisnecessarytoread
theECGrecordingswhilebearinginmindtheclinicalsettingand,ifnecessary,
takingsequentialrecordings.
Inaddition,normalvariantsmaybeobservedintheECGrecording,which
arerelatedtoconstitutionalhabits,chestmalformations,age,etc.Eventran-
sientabnormalitiesmaybedetectedowingtoanumberofcauses(hyperven-
tilation,hypothermia,glucoseoralcoholintake,ionicabnormalities,effectof
certaindrugs,etc.).
Electrocardiography has become even more important than it was at the
beginning. In the twenty-first century, ECG is not only a technique used to
4