Fundamentals of ECG -Introduction

History of electrocardiogram
Indications of electrocardiogram
Electrocardiogram machine
Different types of electrocardiography
Procedure of electrocardiogram
Electrodes and leads
ECG paper
ECG reporting
Recent advancement of electrocardiogram

1. Fundamentals of ECG
Introduction of Electrocardiogram (ECG/EKG)
Dr. Md.ToufiqurRahman
MBBS, FCPS, MD, FACC, FESC, FRCP, FSCAI,
FCCP,FAPSC, FAPSIC, FAHA,FACP
Professor & head of Cardiology
CMMC, Manikganj
Ex professor of cardiology,
NICVD, Dhaka

2. History of electrocardiogram
Indications of electrocardiogram
Electrocardiogram machine
Different types of electrocardiography
Procedure of electrocardiogram
Electrodes and leads
ECG paper
ECG reporting
Recent advancement of electrocardiogram
Fundamentals of ECG
Introduction of Electrocardiogram(ECG/EKG)

3. History of electrocardiogram
Willem Einthoven 1860-1927, Inventor of the first practical ECG in 1903
In 1924, Einthoven was awarded theNobel Prize in Medicinefor his pioneering work
in developing the ECG.
Introduction of Electrocardiogram (ECG/EKG)

4. The first ECG machines were very large and bulky, weighing around 275 Kgs(600 lbs).
History of electrocardiogram
Introduction of Electrocardiogram (ECG/EKG)

5. Figure: ECG from 1957
In 1937,Taro Takemiinvented a new portable electrocardiograph machine
History of electrocardiogram
Introduction of Electrocardiogram (ECG/EKG)

6. Indications of an ECG
toobtaininformationabouttheelectricalfunctionoftheheart.
•Medicalusesforthisinformationarevaried
•oftenneedtobecombinedwithknowledgeofthestructureof
theheartand
•physicalexaminationsignstobeinterpreted.
SomeindicationsforperforminganECGincludethefollowing:
•Chestpainorsuspectedmyocardialinfarction(heartattack),
suchasSTelevatedmyocardialinfarction(STEMI)ornon-ST
elevatedmyocardialinfarction(NSTEMI)
•Symptomssuchasshortnessofbreath,murmurs,
fainting,seizures,funnyturns,orarrhythmiasincludingnew
onsetpalpitationsormonitoringofknowncardiacarrhythmias
•Medicationmonitoring(e.g.,drug-induced QT
prolongation,Digoxintoxicity)andmanagementofoverdose
(e.g.,tricyclicoverdose)
Introduction of Electrocardiogram (ECG/EKG)

7. •Electrolyteabnormalities,suchashyperkalemia
•Perioperativemonitoringinwhichanyformofanesthesiais
involved(e.g.,monitoredanesthesiacare,general
anesthesia).Thisincludespreoperativeasessmentand
intraoperativeandpostoperativemonitoring.
•Cardiacstresstesting
•Computedtomographyangiography(CTA)andmagnetic
resonanceangiography(MRA)oftheheart(ECGisusedto
"gate"thescanningsothattheanatomicalpositionofthe
heartissteady.
•Clinicalcardiacelectrophysiology,inwhichacatheteris
insertedthroughthefemoralveinandcanhaveseveral
electrodesalongitslengthtorecordthedirectionof
electricalactivityfromwithintheheart.
Indications of an ECG
Introduction of Electrocardiogram (ECG/EKG)

8. •ECGscanberecordedasshortintermittenttracings
orcontinuousECGmonitoring.
•Continuousmonitoringisusedforcriticallyill
patients,patientsundergoinggeneralanesthesia,and
patientswhohaveaninfrequentlyoccurringcardiac
arrhythmiathatwouldunlikelybeseenona
conventionalten-secondECG.Continuousmonitoring
canbeconductedbyusingHoltermonitors,internal
andexternaldefibrillatorsandpacemakers,
and/orbiotelemetry.
•Screening
Indications of an ECG
Introduction of Electrocardiogram (ECG/EKG)

9. Screening
•Evidence does not support the use of ECGs among those
without symptoms or at low risk ofcardiovascular
diseaseas an effort for prevention. This is because an ECG
may falsely indicate the existence of a problem, leading
tomisdiagnosis, the recommendation of invasive
procedures, andovertreatment.
•However, persons employed in certain critical occupations,
such as aircraft pilots,may be required to have an ECG as
part of their routine health evaluations.
•Hypertrophic cardiomyopathyscreening may also be
considered in adolescents as part of asports physicalout of
concern forsudden cardiac death.
Indications of an ECG
Introduction of Electrocardiogram (ECG/EKG)

10. Electrocardiogram machine
Introduction of Electrocardiogram (ECG/EKG)

11. •Electrocardiographsarerecordedbymachinesthat
consistofasetofelectrodesconnectedtoacentral
unit.
•EarlyECGmachineswereconstructedwithanalog
electronicswherethesignaldroveamotortoprint
outthesignalontopaper.
•Today,electrocardiographsuseanalog-to-digital
converterstoconverttheelectricalactivityofthe
hearttoadigitalsignal.
•ManyECGmachinesarenowportableandcommonly
includeascreen,keyboard,andprinteronasmall
wheeledcart.
Electrocardiogram machine
Introduction of Electrocardiogram (ECG/EKG)

12. •Recentadvancementsinelectrocardiographyinclude
developingevensmallerdevicesforinclusioninfitness
trackersandsmartwatches.
•Thesesmallerdevicesoftenrelyononlytwoelectrodesto
deliverasinglelead.
•RecordinganECGisasafeandpainlessprocedure.
•Themachinesarepoweredbymainspowerbuttheyare
designedwithseveralsafetyfeaturesincludinganearthed
(ground)lead.
•Otherfeaturesinclude:
Defibrillationprotection:anyECGusedinhealthcare
maybeattachedtoapersonwhorequiresdefibrillationand
theECGneedstoprotectitselffromthissourceofenergy.
Electrocardiogram machine
Introduction of Electrocardiogram (ECG/EKG)

13. •Electrostaticdischargeissimilartodefibrillation
dischargeandrequiresvoltageprotectionupto
18,000volts.
•Additionallycircuitrycalledtherightlegdrivercanbe
usedtoreducecommon-modeinterference(typically
the50or60Hzmainspower).
•ECGvoltagesmeasuredacrossthebodyarevery
small.Thislowvoltagenecessitatesalownoisecircuit
andinstrumentationamplifiers.
•Simultaneousleadrecordings:Earlierdesigns
recordedeachleadsequentially,butcurrentmodels
recordmultipleleadssimultaneously.
Electrocardiogram machine
Introduction of Electrocardiogram (ECG/EKG)

14. •MostmodernECGmachinesincludeautomated
interpretationalgorithms.
•ThisanalysiscalculatesfeaturessuchasthePR
interval,QTinterval,correctedQT(QTc)interval,
PRaxis,QRSaxis,rhythmandmore.
•Theresultsfromtheseautomatedalgorithmsare
considered"preliminary"untilverifiedand/or
modifiedbyexpertinterpretation.
•Despite recent advances,computer
misinterpretationremainsasignificantproblem
andcanresultinclinicalmismanagement.
Electrocardiogram machine
Introduction of Electrocardiogram (ECG/EKG)

15. Telelectrocardiogram
Wireless ECG
12 lead ECG test -standard ECG machine
3 lead ECG monitoring
5 lead ECG monitoring
Cardiac Event Recorder
Cardiac Loop Recorder
Implantable Loop Recorder (ILR)
Stress ECG
Different types of electrocardiography
Introduction of Electrocardiogram (ECG/EKG)

16. Right: 5 lead wireless ECG sensor with sepratetransmitter and receiver. © LifeSync
Left: Low cost compact wireless ECG sensor. © IsansysLifecare.
This is a modern day innovation of the traditional clinical ECG machine with similar
functional capabilities.
Electrodes do not have wirers directly attached to the recording or monitoring machine.
These electrodes can transmit the signal wirelessly over to the receiver in the ECG machine.
•Wireless ECG machine
can offer more
flexibilityfor the
patients.
•useful when combined
with a treadmill test
where the lack of
cables can offer more
freedom of movement
during the test.
Wireless ECG
Introduction of Electrocardiogram (ECG/EKG)

17. •modern adaptation of the original Willem Einthoven ECG machine
based on the Einthoven’s Triangle principles.
•the standard ECG machine used in clinical settings today.
•In 1942 Emanuel Goldberger added 3 more leads know as
augmented limb leads (aVR, aVLand aVF) to Willem Einthoven's
limb leads (I, II & III) and six chest leads (V1, V2, V3, V4, V5 & V6)
forming the basis of the 12 lead ECG.
12 lead ECG test -standard ECG machine
Introduction of Electrocardiogram (ECG/EKG)

18. •used for continuous monitoring of heartbeat, heart rate, and heart
rhythmin critical situations like when the patient is under
anesthesia, in surgery or being transported in an ambulance to a
health center.
•requires the use of 4 electrodes that are placed on each of the
limbs.
•used in combination with other medical devices like an
echocardiogram.
3 lead ECG monitoring
Introduction of Electrocardiogram (ECG/EKG)

19. Occasionallya5leadECGisalsousedformonitoringpurposes.
Ituses4electrodeslikea3leadECGwithanadditional5thelectrode
placedonthechest.
Usuallythesedevicesdonotproduceaprintoutofthe
electrocardiogramandmaynotstoretheinformationforfurther
review.
5lead ECG monitoring
Introduction of Electrocardiogram (ECG/EKG)

20. •aportableECGmonitorthatcanbewornbyapatientforduration
of24to48hourswhilethedevicecontinuouslymonitorstheheart
rhythm.
•fewerleadsthananormalclinicalECGmachine.
•Thepatientisfreetomovearoundandgoaroundtheirusualdaily
routines.
•usefulfordetectingabnormalitiesinheartrhythmthatcouldbe
easilymissedduringaclinicalECGtest,whichlastlessthana
minute.
•Thedeviceisreturnedtothe
doctorattheendofthe
monitoringperiodandthedata
fromthedeviceisretrievedand
analyzed.
HolterMonitor Test
Introduction of Electrocardiogram (ECG/EKG)

21. the symptoms may not appear during the ECG and a HolterMonitor test.
In such cases, a Cardiac Event Recorder can be worn continuously for
an extended period of time (2-4 weeks).
the size of a deck of cards and cables to the recording device connect
the electrodes.
Unlike the HolterMonitor, it continuously record the heart rhythm.
When the patient is experiencing the symptoms, he or she can activate
the recorder and the device will record the incident.
Dependingonthemodelofthedevice,
multipleeventscanberecordedinthe
internalmemory.
Thedatacanbetransferredtothe
consultingdoctorfordetailedanalysisand
thedoctorcanmakeamoreanaccurate
diagnosisbasedondataobtainedduringthe
abnormalincident.
Cardiac event recorder
Introduction of Electrocardiogram (ECG/EKG)

22. •acompactUSBpendrivesizedmedicaldevicetomonitortheheartfunction.
•attachedtothesurfaceoftheskinaroundtheareaofthepatient'sheart.
•continuouslyrecordstheheartrhythmforacertainduration,dependingonthememory
capacityofthedeviceandwhenthedevicememoryisfull,itstartsoverwritingfromthe
beginningoftherecording,Hencethename,looprecorder.
•Aneventrecordercanmissthestartingofanabnormalheartactivityduetothedelayin
initiatingtherecordfunction,Alooprecorderhasarecordbuttonwhenpressedcansave
theimmediatefewminutespriortothestartoftheabnormalheartactivityandcontinue
recordingforfewadditionalminutesandthenstoprecording.Thiswaytheentireepisodeis
capturedandnotoverwritten.
•Whenthepatientexperiencesanabnormalitythe
recordercanbesettoautomaticallyrecordthe
incidentorcanmanuallyinstructthedeviceto
recordtheincident.
•Alooprecordercanbewornformanydaysor
weeks(upto30days),whilethepatientgoes
aroundtheirroutineday-to-dayactivities.Itcanbe
removedduringshoweringorswimming.
Cardiac loop recorder
Introduction of Electrocardiogram (ECG/EKG)

23. •miniaturelooprecorderthatcanbeimplantedbetweenthechestskinandtherib
cage,abovetheheart.
•Likethelooprecorderitcanbeprogrammedtoautomaticallystartrecording
whenanabnormalityisdetectedintheheartrhythm.
•activatedbyanexternaltriggerdevicethatthepatientcancarryaroundinthe
formofawristbandoraremotecontrol.
•moresuitableforpatientswho
experiencesymptomsthatcannotbe
monitoredeasilywithinthe30days’
periodofanormalexternalloop
recorder.
•haveabatterylifeofupto3years
andsuitableforlongtermcontinuous
monitoringinhigh-riskpatients.
Implantable Loop recorder(ILR)
Introduction of Electrocardiogram (ECG/EKG)

24. •alsoknownasCardiacstresstestortreadmilltest.
•Inpatientsthatcanwalk,thetestisconductedonatreadmill.
•ThepatientisconnectedtoanECGmonitoringmachineandisaskedtostart
walkingonthetreadmill.
•Asthetestprogresses,theintensityofthephysicalactivityisincreased.
•Patientswithwalkingdisabilitycanusehandpedalingstationarybike.
•Insomecases,apharmaceuticaldrugisusedtosimulatethesameeffectin
disabledpatients.
•designedthestudyhowthepatient'sheartcancopeupwithaddedexternal
stress.
•abnormalitiesonECGduringthetest
canbeanindicationofunderlying
heartdisease.
•Thetestisusefulforoverall
assessmentofaperson'shealthandis
oftenusedbyprofessionalslike
AviatorsandAstronautsduringtheir
routinehealthcheckups.
Stress ECG
Introduction of Electrocardiogram (ECG/EKG)

25. •safe,noninvasive,painlesstestsandhavenomajorrisks.
•Theelectrodes(stickypatches)thatconnectthesensorstothechestdonotsend
outelectricshocks.
•Theremaydevelopamildrashorskinirritationwheretheelectrodeswere
attached.
•Ifanypasteorgelwasusedtoattachtheelectrodes,theremaybeanallergic
reactiontoit.
•Thisirritationusuallygoesawayoncethepatchesareremoved,withoutrequiring
treatment.
•Ensurethatelectronicdevices(e.g.smartphone)
areremovedfromthepatient.
•Thesedevicescanproduceartifact
(interference)andcauseproblemswiththe
readings.
•PlacepatientinsupineorSemi-Fowler's
position.Ifbothpositionsareimpossible,
performECGwiththepatientinamore
elevatedposition.
Procedure of Electrocardiogram
Introduction of Electrocardiogram (ECG/EKG)

26. Witharmslyingflatontheside,askthepatienttorelaxtheshoulders
andkeepthelegsuncrossed.
Forpatientsthatdonotfitcomfortablyonthebedorexamtabledueto
size,askthemtocrosstheirarmsontheirstomachtoreducemuscle
tensionandmovement.
UnlessperformingastressECGtest,askthepatienttoliestilland
quietlyuntilthetestisdone.
AslightECGartifactisnotuncommon.However,furtherinterferencecan
bereducedthroughthefollowingsteps:
Switchoffnon-essentialelectricaldevicesandequipmentwithin
thevicinityifpossible.
Checkforcableloopsandavoidrunningcablesadjacentto
metallicobjectsastheycanaffectthesignal.
Inspectwiresandcablesforcracksorbreaks.Replaceasneeded.
Ifpossible,usesurgesuppressorswiththepowersupply.
Ensurethatfiltersandpreamplifiersareappropriatelyadjusted.
EnsuresecurelyconnectionbetweenpatientcableandtheECG
device.Doublecheckforgapsbetweenconnectors.
Procedure of Electrocardiogram
Introduction of Electrocardiogram (ECG/EKG)

27. •Anelectrodeisaconductivepadwhichisattachedtotheskinand
enablesrecordingofelectriccurrents.
•AnECGleadisagraphicaldescriptionoftheelectricalactivityofthe
heartanditiscreatedbyanalyzingtheelectricalcurrentsdetected
byseveralelectrodes.
•eachECGlead(equivalenttoadifferentvideocameraangle)
recordsadifferentviewofcardiacelectricalactivity.
•TheuseofmultipleECGleadsisnecessitatedbytherequirementto
generateasfullapictureofthethree-dimensionalelectricalactivity
oftheheartaspossible.
•The12ECGleadsaredividedintotwo
sets:the6extremityleads(3unipolar
and3bipolar),whichrecordvoltages
onthefrontalplaneofthebody;and
the6chest(precordial)leads,which
recordvoltagesonthehorizontalplane.
Electrodes and leads
Introduction of Electrocardiogram (ECG/EKG)

28. •Togetherthese12leadsprovideathree-dimensionalpictureof
atrialandventriculardepolarizationandrepolarization.
•Thereasonforexactly12leadsispartlyhistorical,amatterofthe
waytheECGhasevolvedovertheyearssinceEinthoven'soriginal3
limbleads
•Theheart,afterall,isathree-dimensionalstructure,andits
electricalcurrentsspreadoutinalldirectionsacrossthebody
•heartvoltagesdirectedupwardanddownwardandtotherightand
leftarerecordedbythefrontalplaneleads.
•The six chest leads (V
1through V
6) record
heart voltages transmitted onto
thehorizontalplane of the body
•the chest leads record heart voltages
directed anteriorly (front) and posteriorly
(back), and to the right and left.
Electrodes and leads
Introduction of Electrocardiogram (ECG/EKG)

29. •ThestandardECGhas12leads.Sixoftheleadsareconsidered“limbleads”becausethey
areplacedonthearmsand/orlegsoftheindividual.
•Theothersixleadsareconsidered“precordialleads”becausetheyareplacedonthetorso
(precordium).
•ThesixlimbleadsarecalledleadI,II,III,aVL,aVRandaVF.Theletter“a”standsfor
“augmented,”astheseleadsarecalculatedasacombinationofleadsI,IIandIII.
•ThesixprecordialleadsarecalledleadsV1,V2,V3,V4,V5andV6.
Electrodes and leads
Introduction of Electrocardiogram (ECG/EKG)

30. Electrodes and leads
Introduction of Electrocardiogram (ECG/EKG)

31. Electrodes and leads
Introduction of Electrocardiogram (ECG/EKG)

32. Anatomical relations of leads in a standard 12 lead electrocardiogram
II, III, and aVF: inferior surface of the heart
V1 to V4: anterior surface
I, aVL, V5, and V6: lateral surface
V1 and aVR: right atrium and cavity of left ventricle
Electrodes and leads
Introduction of Electrocardiogram (ECG/EKG)

33. Right sided lead
Electrodes and leads
Introduction of Electrocardiogram (ECG/EKG)

34. Posterior lead
Electrodes and leads
Introduction of Electrocardiogram (ECG/EKG)

35. Lewis lead (S5-lead) placement
•The Lewis lead configuration can help to detect atrial activity and its relationship
to ventricular activity.
•Named after Welsh cardiologistSir Thomas Lewis(1881-1945) who first
described in 1913.
•Useful in:
Observing flutter waves in atrial flutter
Detecting P waves in wide complex tachyarrhythmia
to identify atrioventriculardissociation
Lewis lead placement
Right Arm (RA)electrode on manubrium
Left Arm (LA) electrode over 5th ICS,right sternal border.
Left Leg (LL) electrode over right lower costal margin.
Monitor Lead I
Electrodes and leads
Introduction of Electrocardiogram (ECG/EKG)

36. Colorcoding of 12 lead ECG
IEC (International ElectrotechnicalCommission) system and AHA (American Heart Association) system
If usingAHA's system, use this mnemonic to easily recall limb electrode placement:
smoke over fire (black lead above the red lead) & snow over grass (white lead above the
green lead)
Introduction of Electrocardiogram (ECG/EKG)

37. Electrodes and leads
Electrode Reversal
Introduction of Electrocardiogram (ECG/EKG)

38. Electrodes and leads
FILTERING
•Anelectrocardiogram(ECG)isobtainedanalogand,incurrent
machines,isconvertedintoadigitalsignal,whereitisfilteredto
blockoutsomeofthe“noise”whilekeepingrelevantpartsofthe
“signal.”
•Lowfrequencysignalssuchasrespirationareeliminatedusinga
highpassfilter.
•Highfrequencysignalssuchasnoncardiacmusclepotentialsare
attenuatedusingalowpassfilter.
•Specific“notch”filtersthateliminateelectromagnetic
interferenceat50to60Hzmayalsobeused.
•DigitalECGdatamayalsobecompressedwhensenttoa
databasetoberetrievedforlateruse.
•Therefore,theremaybeasmalldifferenceinappearanceofan
ECGprintedatthebedsideversusonedownloadedfroman
electronicmedicalrecord.
Introduction of Electrocardiogram (ECG/EKG)

39. ECG paper
Introduction of Electrocardiogram (ECG/EKG)

40. ECG paper
The electrocardiogram (ECG) is a plot of voltage on the
vertical axis against time on the horizontal axis.
The electrodes are connected to a galvanometerthat
records a potential difference.
The needle (or pen) of the ECG is deflected a given
distance depending upon the voltage measured.
The ECG waves are recorded on special graph paper
that is divided into 1 mm
2
grid-like boxes .
The ECG paper speed is ordinarily 25 mm/sec. As a
result, each 1 mm (small) horizontal box corresponds
to 0.04 second (40 ms), with heavier lines forming
larger boxes that include five small boxes and hence
represent 0.20 sec (200 ms) intervals.
Introduction of Electrocardiogram (ECG/EKG)

41. ECG paper
On occasion, the paper speed is increased to 50 mm/sec to
better define waveforms. In this situation, there are only six
leads per sheet of paper. Each large box is therefore only
0.10 sec and each small box is only 0.02 sec. In addition, the
heart rate appears to be one-half of what is recorded at 25
mm/sec paper speed, and all of the ECG intervals are twice
as long as normal.Other paper speeds are occasionally
used.
Vertically, the ECG graph measures the height (amplitude) of
a given wave or deflection.
The standard calibration is 10 mm (10 small boxes), equal to
1 mV. On occasion, particularly when the waveforms are
small, double standard is used (20 mm equals 1 mv).
When the wave forms are very large, half standard may be
used (5 mm equals 1 mv). Paper speed and voltage are
usually printed on the bottom of the ECG for reference.
Introduction of Electrocardiogram (ECG/EKG)

42. ECG paper

43. ECG reporting
The ECG ‘Rule of Fours’
Four Initial Features
Four Waves
Four Intervals
The key is to read each ECG methodically, following
the basic structure, looking at all leads.
Introduction of Electrocardiogram (ECG/EKG)

44. TheFOURINITIALFEATUREStolookforonanECG
(1)History/ClinicalPicture
•ThisisTHEMOSTIMPORTANTthingtolookaton
ANYECG.
•ECGisjustlikeanyothertest,andshouldalways
beinterpretedintheclinicalcontext,perhaps
evenmoreso.
•Simplethingsneedtoberecorded,likethename,
age,time,patientsymptoms(e.g.chestpain)and
otherclinicalfeatures.
Introduction of Electrocardiogram (ECG/EKG)
ECG reporting

45. A quick check for lead placement errors:
Limb leads: (a) check aVRfor upside down P, QRS and T waves,
(b) aVLand aVRshould generally be mirror images.
Chest leads: look for RS pattern in V1 –changing progressively
to QR pattern in V6.
(2) Rate
•The normal value is between 60-100/min. Lower than this is
bradycardia, higher is tachycardia.
(3) Rhythm
•Is the rhythm sinus or is it another rhythm? If so, what?
(4) Axis
Introduction of Electrocardiogram (ECG/EKG)
ECG reporting

46. Introduction of Electrocardiogram (ECG/EKG)
ECG reporting