ECG Interpretation: From Pathophysiology to Clinical Application

288 Pages·2009·13.53 MB·English

by  Fred M. Kusumoto (auth.)

ECG INTERPRETATION:
FROM PATHOPHYSIOLOGY
TO CLINICAL APPLICATION
ECG INTERPRETATION:
FROM PATHOPHYSIOLOGY
TO CLINICAL APPLICATION
by
Fred Kusumoto, MD
Electrophysiology and Pacing Service
Division of Cardiovascular Diseases
Department of Medicine
Mayo Clinic
Jacksonville, Florida, USA
123
FredKusumoto,MD
DivisionofCardiovascularDiseases
DepartmentofMedicine
MayoClinic
Jacksonville,Florida,USA
[email protected]
ISBN978-0-387-88879-8 e-ISBN978-0-387-88880-4
DOI10.1007/978-0-387-88880-4
LibraryofCongressControlNumber:2008937757
(cid:2)c SpringerScience+BusinessMedia,LLC2009
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Preface
Why write another book on ECG analysis and interpretation? Although there
areanumberofsuperbintroductoryandcomprehensivebooksonECGinterpreta-
tion,thereareveryfewbooksthatprovidethereaderinformationbeyondthebasics,
otherthanencyclopedictexts.Inaddition,ECGreadinghasbeentraditionallytaught
using “pattern recognition.” However, over the past two decades there has been a
tremendous explosion of basic research that has transformed our understanding of
thebasisoftheECG.Finally,teachingECGshasoftenbeendoneby“stand-alone”
lecturesthathavelittleclinicalcontext;orworse,noorganizedteachingofECGsis
available because of the tremendous demands of the increasing depth and breadth
of medical knowledge that must be mastered during medical school, training, and
beyondtobecomeaconsumateclinician.
This book has been written to fill these gaps. Although this book provides
basicinformationonECGanalysisitalsoattemptstoexplaintheelectrophysiologic
underpinnings for the ECG.Traditional findings such as ST segment elevation are
explained with a “framing” case for each chapter with a series of clinically based
questionsattheenddesignedtohelpthestudentunderstandtheimportanceofthe
ECG in clinical medicine. Finally, the book ends with a discussion and series of
clinicalproblemsthatwillhelpthereaderdevelopapersonalstyleforECGanalysis.
IntheendIhopethereaderfindsthistextusefulforlearninghowtointerpretECGs
inthecontextofpatientcare.
This book grew out of a series of lectures on ECG analysis I have given at
theUniversityofCalifornia,SanFrancisco;theUniversityofNewMexico;andthe
MayoClinic,Jacksonville.Iwouldliketothankthemany students,residents,and
colleaguesthatcontributedtothisproject.Iwouldalsoliketothankmythreemen-
tors that taught me ECG analysis over the years: Nora Goldschlager, Mel Schein-
man, and Tom Evans. I appreciate the patience of Melissa Ramondetta for letting
thisprojectevolveoveraverylongtime.FinallyIwouldliketothankmyfamilyfor
puttingupwiththeconstanttypingandthemissedsoccergamesandschoolplays
thatatasklikethisinevitablyrequires.
vii
Table of contents
PartI: Basicelectrophysiologyandelectrocardiography................. 1
1. Cardiacanatomyandelectrophysiology................................ 3
2. Physicsofelectrocardiography........................................ 11
3. Thenormalelectrocardiogram......................................... 21
PartII: Abnormaldepolarization....................................... 35
4. Chamberenlargement................................................ 37
5. ConductionabnormalitiesintheHis-Purkinjetissue..................... 49
PartIII: Abnormalrepolarization...................................... 63
6. Ventricularrepolarization:TwavesandUwaves........................ 65
7. STsegmentelevationandotherECGfindingsinmyocardialinfarction.... 81
8. STsegmentelevationnotassociatedwithmyocardialinfarction...........111
PartIV: Arrhythmias..................................................127
9. Prematurebeats......................................................129
10.Bradycardia.........................................................139
11.Supraventriculartachycardia..........................................155
12.Widecomplextachycardia............................................183
13.Pacemakers ......................................................... 205
ix
x Tableofcontents
PartV: “Puttingitalltogether” ....................................... 215
14.AnalyzingECGs:Methods,techniques,andidentifyingabnormalities.....217
15.AnalyzingECGs:Puttingittogetherwithcasestudies...................225
16.Electrolytedisorders................................................. 249
17.Orphans.............................................................259
Appendix...............................................................277
Extrapractice“Soyou’reagluttonforpunishment”.........................283
Index .................................................................. 293
Part I
Basic electrophysiology and electrocardiography
Chapter 1
Cardiac anatomy and electrophysiology
Sinceitsdevelopmentintheearly1900sbyEinthoven,theelectrocardiogram
(usually referred to by its acronym, ECG) has become an important tool for eval-
uatingtheheart.Duringthelasttwentyyears,ourunderstandingofthebasicelec-
trophysiology of the heart has dramatically increased, which has provided further
insightintothephysiologicbasisoftheelectrocardiogram.Inthisfirstchapterbasic
electrophysiologyandcardiacanatomywillbereviewed.Althoughtheseprinciples
canbedifficulttounderstand,theyprovideanimportantfoundationforunderstand-
ingthephysiologicandpathophysiologicbasisfortheECG.Inthisway,ratherthan
evaluatingtheECGusing“patternrecognition,”themechanismsforECGchanges
canbeunderstoodandhopefullymoreeasilyremembered.Readersareencouraged
to refer back to this chapter as they read about specific conditions observed in an
ECGinlaterchapters.
ECG:electrocardiogram;EKG:elektrokardiogramm
AlthoughEinthovenperfectedthestringgalvanometerinLeiden,TheNether-
lands,andusedtheacronymEKGtodescribehistracings,asEnglishhasbecome
moredominantintoday’sworld,theacronymECGhasnowbecomemorecommon.
Cardiacelectrophysiology
All cells have a cell membrane that separates the interior and exterior of the
cell.Thecellmembraneallowsdifferentionconcentrationstobemaintainedinthe
intracellular space and extracellular space. The cell membrane is composed of a
phospholipid bilayer, within which cholesterol molecules and proteins are found.
Proteinsareacriticalcomponentofthecellmembrane;theyallowselectivemove-
ment of different ions at different times in the cardiac cycle. For the cardiac cells,
voltage differences between the inside and outside of the cell are generated by
sequential opening and closing of different ion channels. Ion channels are simply
“pores” that, when open, allow passive movement of ions across the cell mem-
brane down the electrical or concentration gradient of the ion. The concentration
differencesofionsbetweentheinsideandoutsideofthecellareformedandmain-
+ +
tainedbytheactionofproteinpumpsandchannels,includingtheNa -K -ATPase
F.Kusumoto,ECGInterpretation:FromPathophysiologytoClinicalApplication, 3
DOI10.1007/978-0-387-88880-4_1,(cid:2)C SpringerScience+BusinessMedia,LLC2009