ECG

1. Basics of ECG reading

2. What is a 12 lead
ECG?
Records the electrical activity of the heart (depolarisation and
repolarisation of the myocardium)
Views the surfaces of the left ventricle from 12 different angles

3. Why do a 12 lead
ECG?
Monitor patients heart rate and rhythm
Evaluate the effects of diseases or injury on heart function
Detect presence of electrolyte and other disturbances

4. Anatomical Position
of the Heart

5. Impulse Conduction & the ECG
Sinoatrial node
AV node
Bundle of His
Bundle Branches
Purkinje fibers

6. The “PQRST”
 P wave - Atrial
depolarization
• T wave - Ventricular
repolarization
• QRS - Ventricular
depolarization

7. Limb leads Chest Leads

8. Limb Leads
3 Unipolar leads
 avR - right arm (+)
 avL - left arm (+)
 avF - left foot (+)
 note that right foot is a ground lead

9. Limb Leads
3 Bipolar Leads
form (Einthovens Triangle)
Lead I - measures electrical potential
between right arm (-) and left arm (+)
Lead II - measures electrical potential
between right arm (-) and left leg (+)
Lead III - measures electrical potential
between left arm (-) and left leg (+)

10. Chest Leads
6 Unipolar leads
Also known as precordial leads
V1, V2, V3, V4, V5 and V6 - all positive

11. Chest Leads

13. Think of the positive electrode as an
‘eye’…
the position of the positive electrode on
the body determines the area of the
heart ‘seen’ by that lead.

14. ECG Waveforms
When an electrical impulse
travels towards a positive
electrode, there will be a
positive deflection on the ECG
If the impulse travels away
from the positive electrode, a
negative deflection will be
seen

15. The Normal EKG
P
Q
R
S
T
Right Arm
Left Leg
QTPR
0.12-0.2 s approx. 0.44 s
Atrial muscle
depolarization
Ventricular muscle
depolarization
Ventricular
muscle
repolarization
“Lead II”

16. Positive electrodes of limb leads
0o
30o
-30o
60o
-60o
-90o
-120o
90o120o
150o
180o
-150o
I
II
avF
avLavR
Limb leads
I = +0o
II = +60o
III = +120o
Augmented leads
avL = -30o
avF = +90o
avR = -150o
I
IIIII

17. AXIS DETERMINATION

18. AXIS
Axis refers to the mean QRS axis
(or vector) during ventricular
depolarization.

19. The QRS Axis
By near-consensus, the
normal QRS axis is defined
as ranging from -30° to +90°.
-30° to -90° is referred to as a
left axis deviation (LAD)
+90° to +180° is referred to as
a right axis deviation (RAD)

20. 0o
30o
-30o
60o
-60o
-90o
-120o
90o120o
150o
180o
-150o
AXIS
… if the QRS is negative in lead I and negative in lead II what is the QRS
axis? (normal, left, right or right superior axis deviation)
QRS Complexes
I
AxisI II
+ +
+ -
- +
- -
normal
left axis deviation
right axis deviation
right superior
axis deviation
0o
30o
-30o
60o
-60o
-90o
-120o
90o120o
150o
180o
-150o
II

21. AXIS
Is the QRS axis normal in this ECG? No, there is left axis
deviation.
The QRS is
positive in I and
negative in II.

22. The ECG Paper
 Horizontally
 One small box - 0.04 s
 One large box - 0.20 s
 Vertically
 One large box - 0.5 mV

23. The standard 12 Lead ECG
6 Limb Leads 6 Chest Leads (Precordial leads)
avR, avL, avF, I, II, III V1, V2, V3, V4, V5 and V6
Rhythm Strip

24. RHYTHM ANALYSIS

25. 69 year old man without symptoms. What is the rhythm?
Sinus rhythm with markedly prolonged PR interval.
(Also, LBBB.)

26. Normal Impulse Conduction
Sinoatrial node
AV node
Bundle of His
Bundle Branches
Purkinje fibers

27. Impulse Conduction & the ECG
Sinoatrial node
AV node
Bundle of His
Bundle Branches
Purkinje fibers

28. The “PQRST”
 P wave - Atrial
depolarization
• T wave - Ventricular
repolarization
• QRS - Ventricular
depolarization

29. Rhythm Analysis
 Step 1: Calculate rate.
 Step 2: Determine regularity.
 Step 3: Assess the P waves.
 Step 4: Determine PR interval.
 Step 5: Determine QRS duration.

30. Step 1: Calculate Rate
 Option 1
 Count the # of R waves in a 6 second rhythm strip, then multiply by 10.
 Reminder: all rhythm strips in the Modules are 6 seconds in length.
Interpretation?
9 x 10 = 90 bpm
3 sec 3 sec

31. Step 1: Calculate Rate
 Option 2
 Find a R wave that lands on a bold line.
 Count the # of large boxes to the next R wave. If the second R wave is 1
large box away the rate is 300, 2 boxes - 150, 3 boxes - 100, 4 boxes - 75,
etc. (cont)
R wave

32. Step 1: Calculate Rate
 Option 2 (cont)
 Memorize the sequence:
300 - 150 - 100 - 75 - 60 - 50
Interpretation?
3
0
0
1
5
0
1
0
0
7
5
6
0
5
0
Approx. 1 box less than
100 = 95 bpm

33. Step 2: Determine regularity
 Look at the R-R distances (using a caliper or
markings on a pen or paper).
 Regular (are they equidistant apart)?
Occasionally irregular? Regularly irregular?
Irregularly irregular?
Interpretation?
Regular
R R

34. Step 3: Assess the P waves
 Are there P waves?
 Do the P waves all look alike?
 Do the P waves occur at a regular rate?
 Is there one P wave before each QRS?
Interpretation?
Normal P waves with 1 P
wave for every QRS

35. Step 4: Determine PR interval
 Normal: 0.12 - 0.20 seconds.
(3 - 5 boxes)
Interpretation?
0.12 seconds

36. Step 5: QRS duration
 Normal: 0.04 - 0.12 seconds.
(1 - 3 boxes)
Interpretation?
0.08 seconds

37. Rhythm Summary
 Rate 90-95 bpm
 Regularity regular
 P waves normal
 PR interval 0.12 s
 QRS duration 0.08 s
Interpretation?
Normal Sinus Rhythm

38. ARRYTHMIAS

39.  Etiology: SA node is depolarizing faster than normal, impulse is
conducted normally.
 Remember: sinus tachycardia is a response to physical or
psychological stress, not a primary arrhythmia.

46. Ventricular Conduction
Normal
Signal moves rapidly
through the ventricles
Abnormal
Signal moves slowly
through the ventricles

47. EMO ASK ABOUT GIVING LIDOCAINE

48. FOLLOWING STRESS TEST RHYTHM SUDDENLY CHANGES PATIENT
ALERT AND DENIES CHEST PAIN

49. Man suddenly collapses while in the aerobic class

50. You are responding to middle aged female who suddenly
lost consciousness in delivery room during birth of the child

51. Motor vehicle accident victim pulse less not breathing

55. 2nd
Degree AV Block
Type 1
(Wenckebach)
EKG Characteristics: Progressive prolongation of the PR interval until a P
wave is not conducted.
As the PR interval prolongs, the RR interval actually
shortens
EKG Characteristics: Constant PR interval with intermittent failure to conduct
Type 2

58. Remember
 When an impulse originates in a ventricle, conduction through the
ventricles will be inefficient and the QRS will be wide and bizarre.

59. Rhythm Analysis
 Step 1: Calculate rate.
 Step 2: Determine regularity.
 Step 3: Assess the P waves.
 Step 4: Determine PR interval.
 Step 5: Determine QRS duration.

60. Normal Impulse Conduction
Sinoatrial node
AV node
Bundle of His
Bundle Branches
Purkinje fibers

61. Bundle Branch Blocks
So, depolarization of
the Bundle Branches
and Purkinje fibers are
seen as the QRS
complex on the ECG.
Therefore, a conduction
block of the Bundle
Branches would be
reflected as a change in
the QRS complex.
Right
BBB

62. Left Bundle Branch Block
Criteria
 QRS duration ≥ 120ms
 Broad R wave in I and V6
 Prominent QS wave in V1
 Absence of q waves (including physiologic q waves) in I and V6

63. Left Bundle Branch Block

64. Right Bundle Branch Block
Criteria
 QRS duration ≥ 110ms
 rSR’ pattern or notched R wave in V1
 Wide S wave in I and V6

65. Right Bundle Branch Block

66. ISCHEAMIA

67. ISCHEMIC CHANGES
 S-T segment elevationS-T segment elevation
 S-T segment depressionS-T segment depression
 Hyper-acute T-wavesHyper-acute T-waves
 T-wave inversionT-wave inversion
 Pathological Q-wavesPathological Q-waves
 Left bundle branch blockLeft bundle branch block

68. ST ELEVATION
One way to diagnose anOne way to diagnose an
acute MI is to look foracute MI is to look for
elevation of the STelevation of the ST
segment.segment.

69. ST-ELEVATION

72. Inferior
II, III, AVF
Septal-Anterior
V1,V2, V3,V4
Lateral
I, AVL, V5,
V6
Posterior
V1,
V2, V3
RIGHT LEFT

73. ST-DEPRESSION
Can be characterised as:-Can be characterised as:-
DownslopingDownsloping
UpslopingUpsloping
HorizontalHorizontal

74. Horizontal ST depression

76. Hyperacute T waves

77. Q Waves
Non Pathological Q wavesNon Pathological Q waves
Q waves of less than 2mm are normalQ waves of less than 2mm are normal
Pathological Q wavesPathological Q waves
Q waves of more than 2mmQ waves of more than 2mm
indicate full thickness myocardialindicate full thickness myocardial
damage from an infarctdamage from an infarct
Late sign of MI (evolved)Late sign of MI (evolved)

78. CHAMBER
ENLARGEMENT

79. Left Atrial Enlargement
Criteria
P wave duration in II ≥120ms
or
Negative component of
biphasic P wave in V1 ≥ 1 “small
box” in area

80. Right Atrial Enlargement
Criteria
P wave height in II ≥ 2.4mm
or
Positive component of
biphasic P wave in V1 ≥ 1
“small box” in area

81. Left Ventricular Hypertrophy
Many sets of criteria for diagnosing LVH have been
proposed:
Sensitivity Specificity
The sum of the S wave in V1 and
the R wave in either V5 or V6 > 35
mm
43% 95%
Sum of the largest precordial R
wave and the largest precordial S
wave > 45 mm
45% 93%
Romhilt-Estes Point System 50-54% 95-97%

82. Left Ventricular Hypertrophy

83. RVH
V1 Lead:
- R/S ratio > 1 and negative T wave
V5 or V6
- R/S ratio in V5 or V6 < 1

84. Right Ventricular Hypertrophy

85. Conclusion
Reading ECG is not difficult
but mastering needs
persistent reading with
sequence.
For diagnoses and
management one has to
combine ECG findings with
patients clinical status.

86. Why do a 12 lead
ECG?
Monitor patients heart rate and rhythm
Evaluate the effects of diseases or injury on heart function
Detect presence of electrolyte and other disturbances

87. ARRYTHMIAS

88. Rhythm assessment
In ACLS recognizing and
treating arrhythmias saves
life.
In chronic rhythm disorder
timely diagnosis guide
major treatment decisions

89. Case-1
60 years man with 2
hours of crushing
chest pain suddenly
collapse

90. ECG - 1

91. Case-2
50 yrs well controlled
HTNsive female on
amlodipine 5mg having
palpitation for last 1 week.

92. ECG – 2
50 yrs well controled hypertensive female on amlodipine 5mg having
palpitation for last 1 week

93. Case-3
70 years old man
with weakness,
lethargy and
exercise intolerance.

94. ECG - 3

95. Case-4
55 yrs male H/O of
Inf. MI 10 yrs back lost
to follow up came to
ER with 2 hours of
palpitations.

96. ECG-4
55 yrs male H/O of Inf. MI 10 yrs back lost to follow up came to
ER with 2 hours of palpitations.

97. Case-5
72 yrs male having
H/O two episodes of
syncope in last two
weeks.

98. ECG – 5
72 yrs male having H/O two episodes of syncope in last two weeks.

99. Clues of cardiac
and non-cardiac
diseases

100. Effects of disease or Injury
Timely diagnosis of acute
diseases guide to specific
life saving treatment.
Chronic disease indicators
provides clues towards
number of cardiac and
non-cardiac diseases.

101. Case-6
40 years female
with 2 hours of
pleuritic chest pain
breathlessness.

102. ECG - 6

103. Case-7
76 years male SOB
for few months
severe for last two
days with
palpitation.

104. ECG - 7

105. Case-8
63 yrs diabetic male
with no other co-
morbids going for
cataract surgery.

106. ECG-863 yrs diabetic male with no other co-morbids going for
cataract surgery.

107. Case-9
A 56 years male
with breathlessness
and raised JVP.

108. ECG - 9

109. ECG - 10

110. ECG- 11
58 yrs diabetic female sudden severe central chest discomfort
for last 15 minutes.

111. ECG- 12
66 yrs male with SOB on minimal exertion since last 1 month.66 yrs male with SOB on minimal exertion since last 1 month.

112. ECG – 13
22 yrs male visited ER for the first time with headache found to have BP of 190/110

113. ECG -14
55 years male, smoker with prolong history of SOB and cough ,
increased in last three month.

114. ECG - 15

115. Conclusion
Reading ECG is not difficult
but mastering needs
persistent reading with
sequence.
For diagnoses and
management one has to
combine ECG findings with
patients clinical status.