BASIC OF ECG

1. Basics of
Electrocardiography

2. Outline
1. Review of the conduction system
2. ECG leads and recording
3. ECG waveforms and intervals
4. Normal ECG and its variants
5. Interpretation and reporting of an ECG

4. What is an ECG?
The electrocardiogram (ECG) is a
representation of the electrical events of the
cardiac cycle.
Each event has a distinctive waveform, the
study of which can lead to greater insight
into a patient’s cardiac pathophysiology.

5. Useful in diagnosis of…
Cardiac Arrhythmias
Myocardial ischemia and infarction
Pericarditis
Chamber hypertrophy
Electrolyte disturbances
Drug effects and toxicity

6. Waveforms and Intervals

7. Recording an ECG

8. Basics
ECG graphs:
–1 mm squares
–5 mm squares
Paper Speed:
–25 mm/sec standard
Voltage Calibration:
–10 mm/mV standard

9. ECG Paper: Dimensions
5 mm
1 mm
0.1 mV
0.04 sec
0.2 sec
Speed = rate
Voltage
~Mass

10. ECG Leads
Leads are electrodes which measure the
difference in electrical potential between either:
1. Two different points on the body (bipolar
leads)
2. One point on the body and a virtual reference
point with zero electrical potential, located in
the center of the heart (unipolar leads)

11. +
-
RA
RA
LL
+
+
-
-
LA
LL
LA
LEAD II
LEAD I
LEAD III
Remember, the RL
is always the ground
• By changing the
arrangement of which
arms or legs are
positive or negative,
three unipolar leads
(I, II & III ) can be
derived giving three
"pictures" of the
heart's electrical
activity from 3 angles.
The Concept of a “Lead”
Leads I, II, and III
I
II III

12. ECG Leads
The standard ECG has 12 leads: 3 Standard Limb Leads
3 Augmented Limb Leads
6 Precordial Leads
The axis of a particular lead represents the viewpoint from
which it looks at the heart.

13. Einthoven’s triangle

17. Standard Limb Leads

18. Standard Limb Leads

19. Augmented Limb Leads

20. All Limb Leads

21. Precordial Leads

22. Precordial Leads

23. Summary of Leads
Limb Leads Precordial Leads
Bipolar I, II, III
(standard limb leads)
-
Unipolar aVR, aVL, aVF
(augmented limb leads)
V1-V6

25. Hexaxial Reference system in
frontal plane

26. Arrangement of Leads on the EKG

27. Anatomic Groups
(Septum)

28. Anatomic Groups
(Anterior Wall)

29. Anatomic Groups
(Lateral Wall)

30. Anatomic Groups
(Inferior Wall)

31. Anatomic Groups
(Summary)

32. Localising the arterial territory
Inferior
II, III, aVF
Lateral
I, AVL,
V5-V6
Anterior /
Septal
V1-V4

33. Interpretation of an ECG

34. Steps involved
Heart Rate
Rhythm
Axis
Wave morphology
Intervals and segments analysis
Chamber enlargement
Specific changes

35. Determining the Heart Rate
Rule of 300
10 Second Rule

36. Rule of 300
Take the number of “big boxes” between
neighboring QRS complexes, and divide this
into 300. The result will be approximately
equal to the rate
Although fast, this method only works for
regular rhythms.

37. The Rule of 300
It may be easiest to memorize the following table:
# of big
boxes
Rate
1 300
2 150
3 100
4 75
5 60
6 50

38. 10 Second Rule
As most ECGs record 10 seconds of rhythm per
page, one can simply count the number of beats
present on the ECG and multiply by 6 to get the
number of beats per 60 seconds.
This method works well for irregular rhythms.

39. The QRS Axis
The QRS axis represents the net overall
direction of the heart’s electrical activity.
Abnormalities of axis can hint at:
Ventricular enlargement
Conduction blocks (i.e. hemiblocks)

40. 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)

41. Determining the Axis
The Quadrant Approach
The Equiphasic Approach

42. Determining the Axis
Predominantly
Positive
Predominantly
Negative
Equiphasic

43. The Quadrant Approach
1. Examine the QRS complex in leads I and aVF to determine
if they are predominantly positive or predominantly
negative. The combination should place the axis into one
of the 4 quadrants below.

44. The Quadrant Approach
2. In the event that LAD is present, examine lead II to
determine if this deviation is pathologic. If the QRS in II is
predominantly positive, the LAD is non-pathologic (in other
words, the axis is normal). If it is predominantly negative, it
is pathologic.

46. Example 1
Negative in I, positive in aVF  RAD

47. Example 2
Positive in I, negative in aVF  Predominantly positive in II 
Normal Axis (non-pathologic LAD)

48. The Equiphasic Approach
1. Determine which lead contains the most equiphasic
QRS complex.
2. The overall QRS axis is perpendicular to the axis of
this particular lead
3. Examine the QRS complex in whichever lead lies 90°
away from the lead identified in step 1
4. If the QRS complex in this second lead is
predominantly positive, than the axis of this lead is
approximately the same as the net QRS axis
5. If the QRS complex is predominantly negative, than
the net QRS axis lies 180° from the axis of this lead.

49. -90°
-60°
-30°
0°
aVL
I
30°
60°
aVR
II
90°
120°
III
150°
180°
-150°
-120°
aVF
Marked RAD
LAD
RAD
Normal Axis
-30° to +100°

50. Example 1
Equiphasic in aVF  Predominantly positive in I  QRS axis ≈ 0°

51. Example 2
Equiphasic in II  Predominantly negative in aVL  QRS axis ≈ +150°

52. Using leads I, II, III
LEAD 1 LEAD 2 LEAD 3
Normal UPRIGHT UPRIGHT UPRIGHT
Physiologic
al Left Axis
UPRIGHT
UPRIGHT /
BIPHASIC
NEGATIVE
Pathological
Left Axis
UPRIGHT NEGATIVE NEGATIVE
Right Axis NEGATIVE
UPRIGHT
BIPHASIC
NEGATIVE
UPRIGHT
Extreme
Right Axis
NEGATIVE NEGATIVE NEGATIVE

53. Common causes of LAD
May be normal in the elderly and very obese
Due to high diaphragm during pregnancy,
ascites, or ABD tumors
Inferior wall MI
Left Anterior Hemiblock
Left Bundle Branch Block
WPW Syndrome
Congenital Lesions
RV Pacer or RV ectopic rhythms
Emphysema

54. Common causes of RAD
Normal variant
Right Ventricular Hypertrophy
Anterior MI
Right Bundle Branch Block
Left Posterior Hemiblock
Left Ventricular ectopic rhythms or pacing
WPW Syndrome

55. Normal Axis
Normal Axis = -30 to +120
RAD =+120 to +180
LAD = -30 to -90
• LAD
• Anterior Hemiblock
• Inferior MI
• WPW – right pathway
• Emphysema
• RAD
• Children, thin adults
• RVH
• Chronic Lung Disease
• WPW – left pathway
• Pulmonary emboli
• Posterior Hemiblock
• No Man’s Land
• Emphysema
• Hyperkalemia
• Lead Transposition
• V-Tach
No Man’s Land Axis
= -90 to +- 180

56. The Normal ECG

57. Normal Sinus Rhythm
Originates in the sinus node
Rate between 60 and 100 beats per min
P wave axis of +45 to +65 degrees, ie.
Tallest p waves in Lead II
Monomorphic P waves
Normal PR interval of 120 to 200 msec
Normal relationship between P and QRS
Some sinus arrhythmia is normal

58. Sinus Arrhythmia
ECG Characteristics: Presence of sinus P waves
Variation of the PP interval which cannot be
attributed to either SA nodal block or PACs
When the variations in PP interval occur in phase with respiration, this is
considered to be a normal variant. When they are unrelated to respiration,
they may be caused by the same etiologies leading to sinus bradycardia.

59. Normal P wave
Atrial depolarisation
Duration 80 to 100 msec
Maximum amplitude 2.5 mm
Axis +45 to +65
Biphasic in lead V1
Terminal deflection should not exceed 1
mm in depth and 0.03 sec in duration

60. Normal QRS complex
Completely negative in lead aVR , maximum
positivity in lead II
rS in right oriented leads and qR in left oriented
leads (septal vector)
Transition zone commonly in V3-V4
RV5 > RV6 normally
Normal duration 50-110 msec, not more than
120 msec
Physiological q wave not > 0.03 sec

61. Normal T wave
Same direction as the preceding QRS
complex
Blunt apex with asymmetric limbs
Height < 5mm in limb leads and <10 mm
in precordial leads
Smooth contours
May be tall in athletes

62. ST segment
Merges smoothly with the proximal limb of
the T wave
Does not ‘hug’ the baseline
No true horizontality

63. Normal u wave
Best seen in midprecordial leads
Height < 10% of preceding T wave
Isoelectric in lead aVL (useful to measure
QTc)
Rarely exceeds 1 mm in amplitude
May be tall in athletes (2mm)

64. QT interval
Normally corrected for heart rate
Bazett’s formula
Normal 350 to 430 msec
With a normal heart rate (60 to 100), the
QT interval should not exceed half of the
R-R interval roughly

65. Normal Variants in the ECG

66. Sinus arrhythmia
Persistent juvenile pattern
Early repolarisation syndrome
Non specific T wave changes

67. Features of ERPS
Vagotonia / athletes’ heart
Prominent J point
Concave upwards, minimally elevated ST segments
Tall symmetrical T waves
Prominent q waves in left leads
Tall R waves in left oriented leads
Prominent u waves
Rapid precordial transition
Sinus bradycardia
Early Recognition Prevents Streptokinase infusion !

68. Normal T wave changes
Inverted in V1-V3: Persistent juvenile
pattern
Inverted normally in
Anxiety
Hyperventilation
Orthostatic
Postprandial

69. Reporting an ECG

70. 1. Patient Details
“ Whose ECG is it ?!”

71. 2. Standardisation and lead
placement
“Is it properly taken ?”
Look for technical Dextrocardia
LV or RV leads?

72. 3. Analysis of Rate, Rhythm
and Axis

73. 4. Segment and wave form
analysis

74. 5. Chamber enlargements

75. 6. Other specific points of
interest based on case history

76. Final Impression
“ Does the ECG correlate with
the clinical scenario ?”

77. Treat the patient and not the
ECG !

78. Thank you !

79. Rajiv Gandhi University of Health Sciences
D.M. Degree Examination - JULY-2018
[Time: 3 Hours] [Max. Marks: 100]
Cardiology - PAPER – I
Basics Sciences
QP Code: 9111
Your answers should be specific to the questions asked.
Draw neat, labeled diagrams wherever necessary. Answer all questions
LONG ESSAY (These questions carry 10 marks each) 10 X 10 = 100 Marks
1. Briefly discuss S2 in health and disease.
2. Pulsus Alternans and Pulsus Bisifierens
3. ECG in Chamber enlargement
4. ECG abnormalities in Electrolyte Abnormalities
5. Assessment of RV function
6. Ankle Brachial Index
7. Myocardial Hibernation
8. Dynamic Auscultation
9. ECHO assessment of Restrictive Cardiomyopathy
10. Abdomino Jugular Reflux

80. Rajiv Gandhi University of Health Sciences D.M Degree
Examination – JULY-2018 Time: Three Hours Max. Marks:
100 Marks Cardiology - PAPER – III Congenital and
Rheumatic Heart Diseases QP Code: 9113 Your answers
should be specific to the questions asked. Draw neat, labeled
diagrams wherever necessary. Answer all questions LONG
ESSAY (These questions carry 10 marks each) 10 x 10 =
100 Marks 1. Diagnosis and management of MVP with MR 2.
Multisystem involvement in CCHD 3. Long term
complications after TOF repair 4. Assessment of operability in
shunt lesions with PH 5. Peripheral pulmonary stenosis –
causes diagnosis and management 6. Paradoxical low flow
low gradient AS – criteria, causes and management 7.
Natural history of biscuspid AV 8. Management of
Multivalvular disease 9. Follow up of a patient with
mechanical prosthetic valve 10. Homograft and autograft
valves * * *

81. Cardiology - PAPER – II Coronary Artery Disease QP Code: 9112 Your
answers should be specific to the questions asked. Draw neat, labeled
diagrams wherever necessary. Answer all questions LONG ESSAY
(These questions carry 10 marks each) 10 x 10 = 100 Marks 1.
Physiologic assessment of coronary artery stenosis 2. Coronary
minovascular dysfunction and its management 3. Approach to acute
chest pain 4. Clinical utility of troponins 5. Universal definitions and
classifications of acute MI 6. Current status of non culprit vessel PCI
acute MI 7. Indications and contraindications thrombolytic therapy 8.
Antiplatelet therapy in a non ST elevation ACS 9. Natural history and
risk stratification in stable angina 10. Thrombus aspiration during PCI –
Current status