Ebook The only EKG book you’ll ever need (9/E): Part 1

TheOnly

EKG
BOOK
You’llEverNeed
NINTHEDITION

MALCOLMS.THALER,M.D.
Physician,InternalMedicine,OneMedical
ClinicalInstructorinMedicine,WeillCornellMedicalCollege
MedicalStaff,NewYorkPresbyterianHospital
NewYork,NewYork


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Ninthedition
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Names:Thaler,MalcolmS.,author.
Title:TheonlyEKGbookyou’lleverneed/MalcolmS.Thaler.
Description:Ninthedition.|Philadelphia:WoltersKluwer,[2019]|Includesindex.
Identifiers:LCCN2017053867|eISBN9781975106072
Subjects:|MESH:Electrocardiography|HeartDiseases—diagnosis|CaseReports
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Dedication

ForNancy,Ali,Jon,andTraceytoo–aswellasforeveryonetoilinginthehealth
careprofession,tryingtomakepeople’sliveshappierandhealthier.


Preface

Thetorridpaceoftechnologicandscientificevolutionshowsnosignsofletting
up,andclinicalmedicineisbothitsbeneficiaryand,conspicuously,itsvictim,
too,asweseemtohavelessandlesstimetoactuallyspendwithourpatients.It
isthereforecomfortingtoknowthatatleastoneoldfriendstillstandstall—the
EKG.Almost30yearshavepassedsincethefirsteditionofthislittlebook,and
nothinghasyetsupplantedtheEKGastheessentialtoolfordiagnosingmany
cardiacdisorders(andmanynoncardiaconesaswell).Doesyourpatienthave
chestpain?—getanEKG!Doesyourpatienthavepalpitations?—getanEKG!
Syncopeordizziness?—yougetthepoint.
Thesethreedecadeshavenotdimmedtheprinciplesoutlinedintheprefaceto
thefirstedition:
Thisbookisaboutlearning.It’saboutkeepingsimplethingssimple,and
complicatedthingsclear,conciseand,yes,simple,too.It’saboutgettingfrom
heretotherewithoutscaringyoutodeath,boringyoutotears,orintimidating

yoursocksoff.It’saboutturningignoranceintoknowledge,knowledgeinto
wisdom,andallwithabitoffun.
IfIwerewritingthistoday,Iwouldprobablyrewordthatbusinessaboutthe
socks,butthesentimentsremainandare,Ihope,onesyoushare.Newmaterial
hasbeenaddedasnewdevelopments—andtherehavebeenmany—havecalled
forit,andeverythingisalwaysdiscussedwithinitsproperclinicalcontextby
puttingyou,thereader,rightinthemiddleofreallifesituations.EKG’sarenot
usedinisolation;theyarejustonepiece—albeitanimportantpiece—ofthe
puzzlethateverypatientpresentsandthatyouandIhavetofigureoutoverand
overagain.
IwanttoofferaveryspecialthankstoDr.AdamSkolnick,M.D.,Associate
ProfessorofMedicine,LeonH.CharneyDivisionofCardiology,NYULangone
MedicalCenter,whosekeeneditorialeye,incisiveanalysis,andunsurpassed
expertisearethebestguaranteethatyouwillbereadingthemostcurrent,clear,
andaccuratetextthatanyonecouldhopefor.Andallowmetoaddashoutoutto


Dr.JeffreyLorin,AssistantProfessorofMedicineatNYUMedicalCenter,who
graciouslyopeneduphisworld-classcollectionofEKG’ssothatweallcould
benefit.
AspecialthankyouasalwaystothewonderfulfolksatWoltersKluwer—let
megiveaverypersonalstandingovationtoKristinaOberleandRebecca
Gaertner—whoalwaysproduceabeautiful,polished,limpidbook(andhavethe
goodsensetoeditoutwordslikelimpidwhenwordssuchasclearandreadable
arefarmoreserviceableand,well,limpid).Theymakeeveryeditionajoyto
workon.
Forthoseofyoupickingupthisbookforthefirsttime—aswellasforthose
ofyoucomingbackforareturnvisit—IhopeTheOnlyEKGBookYouWillEver
NeedprovidesyouwitheverythingyouneedtostartreadingEKG’squicklyand
accurately.

MalcolmS.Thaler,M.D.


Contents
GettingStarted
Chapter1

TheBasics
ElectricityandtheHeart
TheCellsoftheHeart
TimeandVoltage
PWaves,QRSComplexes,TWaves,andSomeStraightLines
NamingtheStraightLines
Summary:TheWavesandStraightLinesoftheEKG
MakingWaves
The12ViewsoftheHeart
AWordAboutVectors
TheNormal12-LeadEKG
Summary:OrientationoftheWavesoftheNormalEKG
SomeReallyImportantStuffThatYouMayBeWondering:Part1:WhyNotJustLettheComputer
DoIt?
SomeReallyImportantStuffThatYouMayBeWondering:Part2:HowDoIGettheGoopOffMy
Patient’sChestOncetheEKGIsFinished?
ComingAttractions
Chapter2

HypertrophyandEnlargementoftheHeart
AFewIntroductoryRemarks
Definitions
Axis

Summary:Axis
AxisDeviation,Hypertrophy,andEnlargement
AtrialEnlargement
Summary:AtrialEnlargement


VentricularHypertrophy
SecondaryRepolarizationAbnormalitiesofVentricularHypertrophy
Summary:VentricularHypertrophy
CASE1
CASE2
Chapter3

Arrhythmias
TheClinicalManifestationsofArrhythmias
WhyArrhythmiasHappen
RhythmStrips
HowtoDeterminetheHeartRateFromtheEKG
TheFiveBasicTypesofArrhythmias
ArrhythmiasofSinusOrigin
Summary:ArrhythmiasofSinusOrigin
EctopicRhythms
ReentrantRhythms
TheFourQuestions
SupraventricularArrhythmias
Summary:SupraventricularArrhythmias
VentricularArrhythmias
Summary:VentricularArrhythmias
SupraventricularVersusVentricularArrhythmias
Summary:VentricularTachycardiaVersusSupraventricularTachycardiaWithAberrancy

ElectrophysiologyStudies(EPS)
ImplantableDefibrillators
ExternalDefibrillators
CASE3
CASE4
CASE5
Chapter4

ConductionBlocks
WhatIsaConductionBlock?
AVBlocks
Summary:AVBlocks


BundleBranchBlock
Summary:BundleBranchBlock
Hemiblocks
CombiningRightBundleBranchBlockandHemiblocks
BlocksThatUnderachieve
TheUltimateinPlayingWithBlocks:CombiningAVBlocks,RightBundleBranchBlock,and
Hemiblocks
Pacemakers
CASE6
CASE7
CASE8
Chapter5

PreexcitationSyndromes
WhatIsPreexcitation?
Wolff–Parkinson–White

AShortPRIntervalWithoutaDeltaWave
WhyDoWeCareAboutPreexcitation?
Summary:Preexcitation
CASE9
Chapter6

MyocardialIschemiaandInfarction
StableAnginaandAcuteCoronarySyndromes
HowtoDiagnoseaMyocardialInfarction
ST-SegmentElevationMyocardialInfarctions(STEMIs)
Summary:TheEKGChangesofanEvolvingSTEMI
LocalizingtheInfarct
Non–ST-SegmentMyocardialInfarctions(non-STEMIs)
TakotsuboCardiomyopathy
AnginaWithoutInfarction
SortingOuttheDifferentIschemicSyndromes
LimitationsoftheEKGinDiagnosinganInfarction
StressTesting
CASE10
CASE11


Chapter7

FinishingTouches
ElectrolyteDisturbances
Hypothermia
Drugs
MoreontheQTInterval
OtherCardiacDisorders

PulmonaryDisorders
CentralNervousSystemDisease
SuddenCardiacDeath
TheAthlete’sHeart
PreparticipationScreeningforAthletes
SleepDisorders
ThePreoperativeEvaluation
Summary:MiscellaneousConditions
CASE12
CASE13
Chapter8

PuttingItAllTogether
The9-StepMethodforReadingEKGs
Chapter9

HowDoYouGettoCarnegieHall?
Index


GettingStarted

Inthischapteryouwilllearn:

1| notathing,butdon’tworry.Thereisplentytocome.Hereisyour
chancetoturnafewpages,takeadeepbreathortwo,andget
yourselfsettledandreadytoroll.Relax.Poursometea.Begin.

Ontheoppositepageisanormalelectrocardiogram,orEKG.1Bythetimeyou
havefinishedthisbook—anditwon’ttakeverymuchtimeatall—youwillbe

abletorecognizeanormalEKGalmostinstantly.Perhapsevenmore
importantly,youwillhavelearnedtospotallofthecommonabnormalitiesthat
canoccuronanEKG,andyouwillbegoodatit!


SomepeoplehavecomparedlearningtoreadEKGswithlearningtoread
music.Inbothinstances,oneisfacedwithacompletelynewnotationalsystem
notrootedinconventionallanguageandfullofunfamiliarshapesandsymbols.
Buttherereallyisnocomparison.Thesimplelub–duboftheheartcannot
approachthesubtlecomplexityofaBeethovenstringquartet(especiallythelate
ones!),themultiplyingtonalitiesandpolyrhythmsofStravinsky’sRiteofSpring,
ortheextraordinaryjazzinterplayofKeithJarrett’sStandardsTrio.
There’sjustnotthatmuchgoingon.


TheEKGisatoolofremarkableclinicalpower,bothbecauseoftheeasewith
whichitcanbemasteredandbecauseoftheextraordinaryrangeofsituationsin
whichitcanprovidehelpfulandevencriticalinformation.Oneglanceatan
EKGcandiagnoseanevolvingmyocardialinfarction,identifyapotentiallylifethreateningarrhythmia,pinpointthechroniceffectsofsustainedhypertensionor
theacuteeffectsofamassivepulmonaryembolus,ordeterminethelikelihoodof
underlyingcoronaryarterydiseaseinapatientwithchestpain.


Remember,however,thattheEKGisonlyatooland,likeanytool,isonlyas
capableasitsuser.Putachiselinmyhandandyouareunlikelytoget
Michelangelo’sDavid.
Theninechaptersofthisbookwilltakeyouonanelectrifying
voyagefromignorancetodazzlingcompetence.Youwillamazeyour
friends(and,moreimportantly,yourself).Theroadmapyouwill
followlookslikethis:

Chapter1:Youwilllearnabouttheelectricaleventsthat
generatethedifferentwavesontheEKG,and—armedwiththis
knowledge—youwillbeabletorecognizeandunderstandthe
normal12-leadEKG.
Chapter2:Youwillseehowsimpleandpredictablealterations
incertainwavespermitthediagnosisofenlargementand
hypertrophyoftheatriaandventricles.
Chapter3:Youwillbecomefamiliarwiththemostcommon
disturbancesincardiacrhythmandlearnwhysomearelife
threatening,whereasothersaremerelynuisances.


Chapter4:Youwilllearntoidentifyinterruptionsinthenormal
pathwaysofcardiacconductionandbeintroducedto
pacemakers.
Chapter5:Youwillseewhathappenswhentheheart’selectrical
currentbypassestheusualchannelsofconductionandarrives
morequicklyatitsdestination.
Chapter6:Youwilllearntodiagnoseischemicheartdisease:
myocardialinfarctions(heartattacks)andangina(painthat
resultswhenregionsoftheheartaredeprivedofoxygen).
Chapter7:Youwillseehowvariousothercardiacand
noncardiacphenomenacanaltertheEKG.
Chapter8:Youwillputallyournewfoundknowledgetogether
intoasimplemethodforreadingallEKGs.
Chapter9:Afewpracticestripswillletyoutestyourknowledge
andrevelinyourastonishingskill.

Thewholeprocessisstraightforwardandshouldnotbetheleastbit
intimidating.Intricaciesofthoughtandgreatleapsofcreativelogicarenot

required.
Thisisnotthetimefordeepthinking.



1Ifyouaresuddenlyworriedthatyouhavepurchasedthewrongbook—“butIwantedtolearnabout

ECG’s,notEKG’s!”—restassuredthatanECGandEKGareoneandthesame.Asmuchaswecangive
credittoanyonepersonforinventingthisremarkabletool,thatcreditbelongstoWillemEinthoven,the
DutchNobelLaureatewhocreatedthefirstrealelectrokardiogrammachine.Noticethe“k”stuckinthe
middlethere?WhereasmostoftheworldhasconvertedtotheEnglishspelling—electrocardiogram,hence
ECG—inAmerica,whereobstinacyistoooftenavirtue,wehaveclungtotheEKGacronym,although
evenherethebondsoftraditionareslowlyloosening.Sopleasecalmdown.Youdon’tpanicwhenyouare
invitedtoabarbecueinsteadofabarbeque,doyou?


1. TheBasics
Foradditionalancillarymaterialsrelatedtothischapter.pleasevisit
thePoint.
Inthischapteryouwilllearn:

1|

howtheelectricalcurrentintheheartisgenerated

2|

howthiscurrentispropagatedthroughthefourchambersofthe
heart

3| thatthemovementofelectricitythroughtheheartproduces
predictablewavepatternsontheEKG
4| howtheEKGmachinedetectsandrecordsthesewaves
5| thattheEKGlooksattheheartfrom12differentperspectives,
providingaremarkablethree-dimensionalelectricalmapofthe
heart

6| thatyouarenowabletorecognizeandunderstandallthelines
andwavesonthe12-leadEKG
thattrustingtheEKGmachinetointerpretyourpatient’sEKGis


7| nothingbutaninvitationtotrouble!

ElectricityandtheHeart
Electricity,aninnatebiologicelectricity,iswhatmakestheheartgo.TheEKGis
nothingmorethanarecordingoftheheart’selectricalactivity,anditisthrough
perturbationsinthenormalelectricalpatternsthatweareabletodiagnosemany
differentcardiacandnoncardiacdisorders.

AllYouNeedtoKnowAboutCellularElectrophysiologyina
FewBriefParagraphs
Cardiaccells,intheirrestingstate,areelectricallypolarized;thatis,theirinsides
arenegativelychargedwithrespecttotheiroutsides.Thiselectricalpolarityis
maintainedbymembranepumpsthatensuretheappropriatedistributionofions
(primarilypotassium,sodium,chloride,andcalcium)necessarytokeepthe
insidesofthesecellsrelativelyelectronegative.Theseionspassintoandoutof
thecellthroughspecialionchannelsinthecellmembrane.

Therestingcardiaccellmaintainsitselectricalpolaritybymeansofamembrane
pump.Thispumprequiresaconstantsupplyofenergy,andthegentlemanabove,
wereherealratherthanametaphor,wouldsoonbeflatonhisback.

Sometimeslethaldisturbancesintheconductionofelectricity
throughtheheartoccurbecauseofaninheriteddisorderofthese
transmembraneionchannels.Fortunately,theseso-called
channelopathiesarequiterare.Manydifferentgeneticmutations
affectingthecardiacionchannelshavebeenidentified,andmore
arebeingdiscoveredeveryyear.
Cardiaccellscanlosetheirinternalnegativityinaprocesscalled
depolarization.Depolarizationisthefundamentalelectricaleventofthe
heart.Insomecells,knownaspacemakercells,itoccursspontaneously.In
others,itisinitiatedbythearrivalofanelectricalimpulsethatcausespositively
chargedionstocrossthecellmembrane.
Depolarizationispropagatedfromcelltocell,producingawaveof
depolarizationthatcanbetransmittedacrosstheentireheart.Thiswaveof
depolarizationrepresentsaflowofelectricity,anelectricalcurrent,thatcanbe
detectedbyelectrodesplacedonthesurfaceofthebody.
Afterdepolarizationiscomplete,thecardiaccellsrestoretheirrestingpolarity
throughaprocesscalledrepolarization.Repolarizationisaccomplishedbythe
membranepumps,whichreversetheflowofions.Thisprocesscanalsobe
detectedbyrecordingelectrodes.
AllofthedifferentwavesthatweseeonanEKGaremanifestationsofthese
twoprocesses:depolarizationandrepolarization.


In(A),asinglecellhasdepolarized.Awaveofdepolarizationthenpropagatesfrom
celltocell(B)untilallaredepolarized(C).Repolarization(D)thenrestoreseachcell’s
restingpolarity.

TheCellsoftheHeart
Fromthestandpointoftheelectrocardiographer,theheartconsistsofthreetypes
ofcells:
Pacemakercells—undernormalcircumstances,theelectricalpowersource
oftheheart
Electricalconductingcells—thehardwiringoftheheart
Myocardialcells—thecontractilemachineryoftheheart


PacemakerCells
Pacemakercellsaresmallcellsapproximately5to10μmlong,aboutthesame
asthewidthofasinglestrandofaspider’sweb.Thesecellsareableto
depolarizespontaneouslyoverandoveragain.Therateofdepolarizationis
determinedbytheinnateelectricalcharacteristicsofthecellandbyexternal
neurohormonalinput.Eachspontaneousdepolarizationservesasthesourceofa
waveofdepolarizationthatinitiatesonecompletecycleofcardiaccontraction
andrelaxation.

Apacemakercelldepolarizingspontaneously.

Ifwerecordoneelectricalcycleofdepolarizationandrepolarizationfroma


singlecell,weobtainanelectricaltracingcalledanactionpotential.Witheach
spontaneousdepolarization,anewactionpotentialisgenerated,whichinturn
stimulatesneighboringcellstodepolarizeandgeneratetheirownaction
potential,andsoonandon,untiltheentirehearthasbeendepolarized.

Atypicalactionpotential.

Theactionpotentialofacardiacpacemakercelllooksalittledifferentthanthe
genericactionpotentialshownhere.Apacemakercelldoesnothaveatrue
restingpotential.Itselectricalchargedropstoaminimalnegativepotentialof
approximately−60mV,whichitmaintainsforjustamoment(itdoesnotrest
there),andthengraduallyrisesuntilitreachesthethresholdforthesudden
depolarizationthatisanactionpotential.Theseeventsareillustratedonthe
followingtracing.

Theelectricaldepolarization–repolarizationcycleofacardiacpacemakercell.PointA
istheminimalnegativepotential.ThegentlerisingslopebetweenpointsAandB
representsaslow,gradualdepolarization.AtpointB,thethresholdiscrossedandthe
celldramaticallydepolarizes(asseenbetweenpointsBandC);thatis,anaction
potentialisproduced.ThedownslopebetweenpointsCandDrepresents
repolarization.Thiscyclewillrepeatoverandoverfor,letushope,many,manyyears.

Thedominantpacemakercellsintheheartarelocatedhighupintheright
atrium.Thisgroupofcellsiscalledthesinoatrial(SA)node,orsinusnodefor
short.Thesecellstypicallyfireatarateof60to100timesperminute,butthe
ratecanvarytremendouslydependingupontheactivityoftheautonomic


nervoussystem(e.g.,sympatheticstimulationfromcatecholamines,suchas
epinephrineandnorepinephrine,acceleratesthesinusnode,whereasvagal
stimulationslowsit)andthedemandsofthebodyforincreasedcardiacoutput
(exerciseraisestheheartrate,whereasarestfulafternoonnaplowersit).
Pacemakercellsarereallygoodatwhattheydo.Theywill
continuefiringinadonorheartevenafterithasbeenharvestedfor
transplantandbeforeithasbeenconnectedtothenewrecipient.
Thetransplantedheart,devoidofnormalvagalstimulation(the

nervesarecutwhenthenewheartisimplanted),beatsatan
averagerateof100beatsperminute(bpm).

Inarestingindividual,thesinusnodetypicallyfires60to100timesperminute,
producingaregularseriesofactionpotentials,eachofwhichinitiatesawaveof
depolarizationthatwillspreadthroughtheheart.

Actually,everycellinthehearthastheabilitytobehavelikea
pacemakercell.Thisso-calledautomaticabilityisnormally
suppressedunlessthedominantcellsofthesinusnodefailorif
somethingintheinternalorexternalenvironmentofacell
(sympatheticstimulation,cardiacdisease,etc.)stimulatesits
automaticbehavior.Thistopicassumesgreaterimportancelateron
andisdiscussedunderEctopicRhythmsinChapter3.


ElectricalConductingCells
Electricalconductingcellsarelong,thincells.Likethewiresofanelectrical
circuit,thesecellscarrycurrentrapidlyandefficientlytodistantregionsofthe
heart.Theyare,ineffect,theelectricalhighwayoftheheart.
Theelectricalconductingcellsoftheventriclesformdistinctelectrical
pathways.Theventricularconductingfibersconstitutewhatiscalledthe
Purkinjesystem.
Theconductingpathwaysintheatriahavemoreanatomicvariability;
prominentamongthesearefibersatthetopoftheintra-atrialseptuminaregion
calledBachmann’sbundlethatallowforrapidactivationoftheleftatriumfrom
theright.

Thehardwiringoftheheart.

MyocardialCells
Themyocardialcellsconstitutebyfarthelargestpartofthehearttissue.They
areresponsiblefortheheavylaborofrepeatedlycontractingandrelaxing,
therebydeliveringbloodtotherestofthebody.Thesecellsareabout50to100
μminlengthandcontainanabundanceofthecontractileproteinsactinand
myosin.