This document provides an agenda and materials for an ECG workshop. The agenda covers anatomy and physiology of the heart, understanding the ECG, and ischaemia and myocardial infarction. The materials go into detail on heart anatomy, blood flow, the conduction system, lead placement, understanding the PQRST complex, and analyzing ECGs. Key points covered include the chambers and layers of the heart, coronary arteries, electrical events in the cardiac cycle, and identifying normal vs. pathological features on an ECG such as the ST segment and Q waves.

1. An ECG WorkshopAn ECG Workshop
Dr Shibu Chacko MBEDr Shibu Chacko MBE
Email:shibu.chacko@nhs.netEmail:shibu.chacko@nhs.net

2. AGENDAAGENDA
 Anatomy and physiology of the heartAnatomy and physiology of the heart
 Understanding the ECGUnderstanding the ECG
 Ischaemia and myocardial infarctionIschaemia and myocardial infarction

3. Anatomy And Physiology OfAnatomy And Physiology Of
The HeartThe Heart

4. The Chambers Of The HeartThe Chambers Of The Heart

5. Blood Flow Through the HeartBlood Flow Through the Heart
•Blood flows from Superior andBlood flows from Superior and
Inferior Vena Cava to the RightInferior Vena Cava to the Right
AtriumAtrium
•Flows through the TricuspidFlows through the Tricuspid
(AV) Valve to the Right Ventricle(AV) Valve to the Right Ventricle
•Blood leaves the RV throughBlood leaves the RV through
the pulmonary trunkthe pulmonary trunk
•Enters lungs via the Right andEnters lungs via the Right and
Left pulmonary arteriesLeft pulmonary arteries

6. Blood Flow Through TheBlood Flow Through The
HeartHeart
•After gas exchange in theAfter gas exchange in the
lungs, blood is transported tolungs, blood is transported to
the left atrium through thethe left atrium through the
Right and Left pulmonaryRight and Left pulmonary
veinsveins
•Blood flows through the MitralBlood flows through the Mitral
Valve into the Left VentricleValve into the Left Ventricle
•The Left Ventricle is the mainThe Left Ventricle is the main
pump that pumps the blood topump that pumps the blood to
the body via the aortathe body via the aorta

7. The Layers Of The Heart WallThe Layers Of The Heart Wall
 EpicardiumEpicardium – outer layer, also called the– outer layer, also called the
visceral layervisceral layer
 MyocardiumMyocardium – middle layer, composed– middle layer, composed
of cardiac muscle tissue, thicker at theof cardiac muscle tissue, thicker at the
left ventricle to give more pumpingleft ventricle to give more pumping
powerpower
 EndocardiumEndocardium – inner layer, lines the– inner layer, lines the
heart chambers and the valvesheart chambers and the valves

8. The Coronary ArteriesThe Coronary Arteries

9. The Coronary ArteriesThe Coronary Arteries
 Right Coronary Artery –Right Coronary Artery –
supplies the RA, RV and asupplies the RA, RV and a
portion of the LVportion of the LV
 Left Main Coronary Artery –Left Main Coronary Artery –
divides into:divides into:
 Left Anterior Descending –Left Anterior Descending –
supplies the anterior part ofsupplies the anterior part of
the LV and the septumthe LV and the septum
 Circumflex – supplies the LACircumflex – supplies the LA
and posterior LVand posterior LV

10. The Conduction SystemThe Conduction System
•Heart is an efficient pumpHeart is an efficient pump
because it is co-ordinated bybecause it is co-ordinated by
the conduction systemthe conduction system
•It controls the heart via aIt controls the heart via a
network of specialised fibresnetwork of specialised fibres
which initiate and conduct thewhich initiate and conduct the
electrical impulse that results inelectrical impulse that results in
muscle contractionmuscle contraction

11. Understanding The ECGUnderstanding The ECG

12. Lead PlacementLead Placement
 Limb leads – Ride YourLimb leads – Ride Your
Green Bike!Green Bike!
 V1- 4V1- 4thth
intercostal spaceintercostal space
to the right of sternumto the right of sternum
 V2- As above but to theV2- As above but to the
leftleft
 V3- Midway between V2V3- Midway between V2
and V4 (do V4 first)and V4 (do V4 first)
 V4- Mid clavicular, 5V4- Mid clavicular, 5thth
intercostal spaceintercostal space
 V5- Anterior axillaryV5- Anterior axillary
line, horizontal to V4line, horizontal to V4
 V6- Mid axillary line,V6- Mid axillary line,
horizontal to V4 and V5horizontal to V4 and V5
 Shave excess hair
 For limb leads place at
wrists and close to ankle
 If patient shaking go for
bony areas

13. ArtifactArtifact
 It is important that an ECG is free from any artefactIt is important that an ECG is free from any artefact
when using it to make a diagnosis.when using it to make a diagnosis.
 Causes of artefact can be:Causes of artefact can be:
 Poor application of ECG electrodes (Dried out gel, air trappedPoor application of ECG electrodes (Dried out gel, air trapped
under electrode & patient hair preventing good skin contactunder electrode & patient hair preventing good skin contact
 Patient’s movementPatient’s movement
 Electrical interferenceElectrical interference
 Cable movementCable movement
 Vehicle movementVehicle movement

14. ECG Showing ArtifactECG Showing Artifact
The following ECG demonstrates what can happen withThe following ECG demonstrates what can happen with
poor preparationpoor preparation
This ECG has a wandering baseline in V1, V4 & V5
and no data from V6

15. Lead ViewsLead Views
 Limb leads look from aLimb leads look from a
‘vertical plane’‘vertical plane’
 I and AVL look from the leftI and AVL look from the left
side - lateral wallside - lateral wall
 II, III and AVF look up fromII, III and AVF look up from
the bottom of the heart –the bottom of the heart –
inferior wallinferior wall
 AVR looks from the right,AVR looks from the right,
but use that to tell you if thebut use that to tell you if the
leads are on wrong!leads are on wrong!

16. Lead ViewsLead Views
 V1 + V2 – SeptalV1 + V2 – Septal
 V3 + V4 – Anterior viewV3 + V4 – Anterior view
 V5 + V6 – Lateral viewV5 + V6 – Lateral view

17. R Wave ProgressionR Wave Progression
1
r
2
S V1
1
2
V6
1
q
R
2
V1 V2 V3
V4 V5 V6

18. Right Sided and PosteriorRight Sided and Posterior
ECGsECGs
 Right sided should beRight sided should be
done if patient is havingdone if patient is having
an Inferior MIan Inferior MI
 Could changeCould change
management ofmanagement of
hypotension in post MIhypotension in post MI
patientpatient
 Look for ST elevation inLook for ST elevation in
rV4rV4
 Ensure is clearly labelledEnsure is clearly labelled
 Posterior ECG – may notPosterior ECG – may not
change treatmentchange treatment

19. ECG PaperECG Paper
•Paper speed should be set to
25mm/sec
•Each small square = 0.04 sec
•Each large square = 0.20 sec
•5 small squares = 0.20 sec
denoted by a heavy line

20. ECG Electrical DeflectionECG Electrical Deflection
 When an electrical impulse travels towards anWhen an electrical impulse travels towards an
electrode the ECG will record aelectrode the ECG will record a positivepositive or upwardor upward
deflection (A)deflection (A)
 When an electrical impulse travels away from anWhen an electrical impulse travels away from an
electrode the ECG will record aelectrode the ECG will record a negativenegative oror
downward deflection (B)downward deflection (B)
A
B
Current Electrode Deflection

21. Electrical Events Of TheElectrical Events Of The
Cardiac CycleCardiac Cycle
 Resting Heart MuscleResting Heart Muscle ==
PolarisedPolarised
 Contraction caused byContraction caused by
stimulation =stimulation =
DepolarisationDepolarisation
 Heart muscle cellsHeart muscle cells
return to resting statereturn to resting state
following stimulation =following stimulation =
RepolarisationRepolarisation
 Resultant depolarisationResultant depolarisation
and repolarisation areand repolarisation are
represented on therepresented on the
ECG by characteristicECG by characteristic
waveforms: Thewaveforms: The
PQRST ComplexPQRST Complex

22. The ECG ComplexThe ECG Complex
 P wave = AtrialP wave = Atrial
DepolarisationDepolarisation
 QRS complex =QRS complex =
VentricularVentricular
DepolarisationDepolarisation
 ST segment = timeST segment = time
between Ventricularbetween Ventricular
Depolarisation andDepolarisation and
VentricularVentricular
RepolarisationRepolarisation
 T wave = VentricularT wave = Ventricular
RepolarisationRepolarisation

23. The PQRST ComplexThe PQRST Complex
 The Isoelectric lineThe Isoelectric line
is the flat line -is the flat line -
baselinebaseline
Isoelectric line

24. The P WaveThe P Wave
 RepresentsRepresents
depolarisation of atrialdepolarisation of atrial
muscle cellsmuscle cells
 Precedes each QRSPrecedes each QRS
complexcomplex
 Normally positiveNormally positive
 Gently roundedGently rounded
 Height <3mmHeight <3mm
 Width <0.11secWidth <0.11sec
 Measured from veryMeasured from very
beginning to the end ofbeginning to the end of
the waveformthe waveform

25. The PR IntervalThe PR Interval
 Measured from theMeasured from the
beginning of the P wavebeginning of the P wave
to the beginning of theto the beginning of the
QRS complexQRS complex
 Represents totalRepresents total
amount of time requiredamount of time required
for depolarisation offor depolarisation of
atria and for impulse toatria and for impulse to
travel through the AVtravel through the AV
nodenode
 Normal width = 0.12-Normal width = 0.12-
0.20 sec (3-5 small0.20 sec (3-5 small
squares)squares)
PR interval

26. The QRS ComplexThe QRS Complex
 Represents ventricularRepresents ventricular
depolarisationdepolarisation
 Results of simultaneousResults of simultaneous
depolarisation of bothdepolarisation of both
ventriclesventricles
 Follows each P waveFollows each P wave
 Q wave not normallyQ wave not normally
present, but small Qspresent, but small Qs
maybe visiblemaybe visible
 Predominantly positivePredominantly positive
 Width <0.11 secWidth <0.11 sec

27. The ST SegmentThe ST Segment
 Interval between theInterval between the
end of the QRS andend of the QRS and
beginning of the T wavebeginning of the T wave
 Represents beginningRepresents beginning
of ventricularof ventricular
repolarisationrepolarisation
 Normally Isoelectric –Normally Isoelectric –
neither above or belowneither above or below
the baselinethe baseline
 Shape and postion mayShape and postion may
be altered due tobe altered due to
ischaemia, drug orischaemia, drug or
metabolic effectsmetabolic effects

28. ST SegmentST Segment
Normal ST
Depression
ST Elevation

29. The T WaveThe T Wave
 Normally follows a QRSNormally follows a QRS
complexcomplex
 Represents the end ofRepresents the end of
repolarisation of therepolarisation of the
ventriclesventricles
 Should be a positiveShould be a positive
deflectiondeflection

30. The QT IntervalThe QT Interval
 Represents the timeRepresents the time
from start of ventricularfrom start of ventricular
depolarisation to end ofdepolarisation to end of
ventricularventricular
repolarisationrepolarisation
 QT interval variesQT interval varies
depending on rate. Isdepending on rate. Is
longer with bradycardialonger with bradycardia
and shorter withand shorter with
tachycardiatachycardia
 Is influenced byIs influenced by
electrolyte imbalance,electrolyte imbalance,
ischaemia and drugsischaemia and drugs
QT interval

31. The J PointThe J Point

32. J Point ExamplesJ Point Examples

33. Pathological Q WavesPathological Q Waves
> 0.04 sec wide
>25% of R wave

34. Pathological Q WavesPathological Q Waves
 The following factors must be taken into considerationThe following factors must be taken into consideration
when assessing the Q wave significance in AMIwhen assessing the Q wave significance in AMI
 The presence of associated LBBBThe presence of associated LBBB
 The width and depth of the Q waveThe width and depth of the Q wave
 The specific leads in which the Q wave appearThe specific leads in which the Q wave appear
 The number of leads in which the Q wave appearThe number of leads in which the Q wave appear
 Other ECG evidence of a MIOther ECG evidence of a MI

35. Calculation of Heart RateCalculation of Heart Rate

36. ““Big Square Method”Big Square Method”
 Easy but only accurate if rhythm is regularEasy but only accurate if rhythm is regular
 Count the number of large squares between twoCount the number of large squares between two
QRS complexes (R wave to R wave)QRS complexes (R wave to R wave)
 Divide the number of large squares into 300Divide the number of large squares into 300

37. 1500 Method1500 Method
 Most precise way to determine rateMost precise way to determine rate
 Can only be used if rhythm is regularCan only be used if rhythm is regular
 Count number of small squares between twoCount number of small squares between two
QRS complexes (R wave to R wave)QRS complexes (R wave to R wave)
 Divide the number of small squares into 1500Divide the number of small squares into 1500

38. 6 Second Method6 Second Method
 Not very accurate, but easyNot very accurate, but easy
 Useful when rhythm is irregularUseful when rhythm is irregular
 Note the small vertical lines at the top of the ECGNote the small vertical lines at the top of the ECG
paper. These represent 3 second intervalspaper. These represent 3 second intervals
 Count the number of QRS complexes in 6 secondsCount the number of QRS complexes in 6 seconds
and multiply by tenand multiply by ten

39. 7 Point Analysis of An ECG7 Point Analysis of An ECG
1. Rhythm1. Rhythm Regular?Regular?
Irregular?Irregular?
Irregularly irregular?Irregularly irregular?
2. Rate2. Rate Normal?Normal?
Bradycardic? <60Bradycardic? <60
Tachycardic? >100Tachycardic? >100
3. P Waves3. P Waves Present/absent?Present/absent?
A P wave for every QRS complex?A P wave for every QRS complex?
Same size and shape?Same size and shape?

40. 7 Point Analysis Of An ECG7 Point Analysis Of An ECG
4. PR Interval4. PR Interval Normal? (0.12-0.20sec)Normal? (0.12-0.20sec)
Too short or too long?Too short or too long?
5. QRS Comlexes5. QRS Comlexes Normal? (<0.11sec)Normal? (<0.11sec)
Too wide?Too wide?
6. ST segment6. ST segment Normal?Normal?
Elevated/depressedElevated/depressed
7. T Wave7. T Wave Normal?Normal?
Unusually raised?Unusually raised?
Inverted?Inverted?

41. A Normal 12 Lead ECGA Normal 12 Lead ECG
 All ST segments remain on the isoelectric line.All ST segments remain on the isoelectric line.
 aVR should always be negative.aVR should always be negative.
 ST elevation in V1-V2 may be a normal variant.ST elevation in V1-V2 may be a normal variant.
 T wave inversion in V1-V2 may be a normal variant.T wave inversion in V1-V2 may be a normal variant.

42. Ischaemia and MyocardialIschaemia and Myocardial
InfarctionInfarction

43. Coronary Heart Disease ProcessCoronary Heart Disease Process

44. IschaemiaIschaemia
 Inadequate myocardial oxygen supply.Inadequate myocardial oxygen supply.
 Can present with ST depression or T wave inversion.Can present with ST depression or T wave inversion.

45. Myocardial InfarctionMyocardial Infarction
 An MI occurs when an area of myocardiumAn MI occurs when an area of myocardium
becomes irreversibly necroticbecomes irreversibly necrotic
 Most common cause is thromboembolicMost common cause is thromboembolic
occlusion of a coronary arteryocclusion of a coronary artery

46. Myocardial InfarctionMyocardial Infarction
 An atheroscleroticAn atherosclerotic
plaque ruptures theplaque ruptures the
intima of an arteryintima of an artery
causing it to come intocausing it to come into
contact with thecontact with the
circulating bloodcirculating blood
 The uneven surfaceThe uneven surface
allows platelets toallows platelets to
adhere to it. Thereforeadhere to it. Therefore
forming a clot, blockingforming a clot, blocking
the artery and stoppingthe artery and stopping
blood flowblood flow

47. Acute Myocardial InfarctionAcute Myocardial Infarction
 ST elevation >2mm in V1-V3 and >1mm in all other leads in >2ST elevation >2mm in V1-V3 and >1mm in all other leads in >2
contiguous leadscontiguous leads11
..
 Myocardial injury presents as raised STMyocardial injury presents as raised ST11
..
 Infarction can present as Q waveInfarction can present as Q wave11
..
I Lateral
aVL LateralII Inferior
III Inferior aVF Inferior
aVR V1 Septal
V2 Septal
V3 Anterior
V4 Anterior
V5 Lateral
V6 Lateral
1. The Task Force on the management of acute myocardial infarction of the

48. Evolution Of An Acute MIEvolution Of An Acute MI
Onset 15 Minutes > 1 Hour
> 24 Hours
Days
Later
Months
later

49. Inferior AMI
II, III, AVF
Septal AMI
V1, V2
Anterior AMI
V3, V4
Lateral AMI
V5, V6 - ( I, AVL )
Location Of Infarctions

50. Acute Myocardial InfarctionAcute Myocardial Infarction
DiagnosisDiagnosis
 Patient storyPatient story
 ECG changesECG changes
 Raised cardiacRaised cardiac
enzymesenzymes
SymptomsSymptoms
 Central chestCentral chest
pain/tightness orpain/tightness or
pressurepressure
 Severe prolongedSevere prolonged
painpain
 Cold and clammyCold and clammy
 Nausea andNausea and
vomitingvomiting
 ArrhythmiasArrhythmias

51. Assessment of Pain - PQRSTAssessment of Pain - PQRST
 Position – where is it?Position – where is it?
 Qualities – what is it like?Qualities – what is it like?
what makes it start and stop?what makes it start and stop?
 Radiation – does it go anywhere else?Radiation – does it go anywhere else?
 Symptoms – are there any other symptoms?Symptoms – are there any other symptoms?
 Timing – when did it start?Timing – when did it start?
how long has it lasted?how long has it lasted?

52. III
aVF
II
I aVR V1 V4
II aVL V2 V5
III aVF V3 V6
Inferior MI

53. I
II
III
aVR
aVL
aVF
V1
V2
V3
V4
V5
V6
V1
V2
V3
V4
Antero-Septal MI

54. V1 V2
V3
V4
V5
V6
aVL
I
I
II
III
aVR
aVL
aVF
V1
V2
V3
V4
V5
V6
Antero-Lateral MI

55. aVL
I
I
II
III
aVR
aVL
aVF
V1
V2
V3
V4
V5
V6
Lateral MI

56. ? Posterior MI – ST Depression V1-V4

57. Dynamic Changes In AMIDynamic Changes In AMI
Pre-hospital ECG showing possible hyperacute
S-T changes in anterior leads

58. Dynamic Changes in AMIDynamic Changes in AMI
2nd ECG taken 20mins later, showing established
antero-lateral S-T elevation

59.  Normally both bundle branches transmit aNormally both bundle branches transmit a
stimulus to the 2 ventricles simultaneously.stimulus to the 2 ventricles simultaneously.
 The QRS duration will be less than 0.12 secondsThe QRS duration will be less than 0.12 seconds
(3 small squares).(3 small squares).
 If one of the bundle branches is blocked, aIf one of the bundle branches is blocked, a
ventricle may be depolarised through an abnormalventricle may be depolarised through an abnormal
pathway outside the main conduction systempathway outside the main conduction system
causing the QRS duration to be greater than 0.12causing the QRS duration to be greater than 0.12
seconds.seconds.
Bundle Branch
Block

60.  To be able to identify which bundle branch is blocked, youTo be able to identify which bundle branch is blocked, you
will need to know which leads best show the resultingwill need to know which leads best show the resulting
abnormality.abnormality.
 The leads looking directly at the right ventricle are V1 & V2.The leads looking directly at the right ventricle are V1 & V2.
 The leads looking at the left ventricle are V5,V6 & leadThe leads looking at the left ventricle are V5,V6 & lead I.I.
V1 V2
V5
V6
I
Left Limb
Lead
ECG Leads

61. V1
QS
 LBBB produces a QS (negative complex) inLBBB produces a QS (negative complex) in
V1 and wide notched complexes in the LeftV1 and wide notched complexes in the Left
limb / chest leads (limb / chest leads (II, V5 & V6)., V5 & V6).
I V5 V6
Left Bundle Branch Block

62. Left Bundle Branch Block

63. Left Bundle Branch BlockLeft Bundle Branch Block
 This can be a pre-existing condition but is alwaysThis can be a pre-existing condition but is always
pathological.pathological.
 Causes include either a new or old MI. Can also beCauses include either a new or old MI. Can also be
a degenerative change.a degenerative change.
 It also causes ST / T wave changes, with T waveIt also causes ST / T wave changes, with T wave
inversion in the left ventricular leads.inversion in the left ventricular leads.
A new LBBB caused by an Acute Coronary
Syndrome identifies a very high risk patient
associated with > 40% mortality without
treatment

64. Right Bundle Branch BlockRight Bundle Branch Block

65. R
R
RBBB
VI-V2 V5-V6
LBBB
Use V1 to identify the terminal force to determine if it
is positive or negative.
RBBB V LBBB

66. AMI ECG Imitators
“Caution” The following ECGs can show
ST segment changes
– Left Bundle Branch Block
– Left Ventricular Hypertrophy
– Paced Rhythm
– Ventricular Rhythms
– Early Repolarisation
– Pericarditis
– Ventricular Aneurysm
This shows the importance of using an ECG along
with the clinical findings & not in isolation.

67. Left Ventricular Hypertrophy
Recognition:
• Compare V1 & V2, determine which has the deeper S
wave & measure the depth in mm (1mm = 1 small square).
• Compare V5 & V6, determine which has the taller R wave
& measure the height (mm).
• Add together the depth & height (mm). If the sum equals
35mm or more, then suspect LVH.

68. Paced Rhythm

69. Pericarditis

70. Early Repolarisation

71. Ventricular Rhythm

72. Ventricular Aneurysm

73. Summary
There are a number of ECGs that can
mimic ST segment changes as seen in
acute coronary syndrome (ACS). This
shows that it is important to evaluate the
clinical signs and symptoms first, then
follow up with confirmation from the ECG

74. Case Study 1 ECGCase Study 1 ECG

75. Case Study 2 ECGCase Study 2 ECG

76. Case Study 3 ECGCase Study 3 ECG

77. Case Study 4 ECGCase Study 4 ECG

78. Case Study 5 ECGCase Study 5 ECG

79. Case Study 6 ECGCase Study 6 ECG

80. Case Study 7 ECGCase Study 7 ECG