ECG IN 100 STEPS

By

Dr. S. Aswini Kumar MD

1. ECG - Electro-cardio- gram

2. ECG - Graphical recording of electrical

activity of human heart

3. ECG - Does not always have a direct correlation with

mechanical activity of heart

4. ECG reading - not a Bali-kera-mala

5. ECG reading - simple arithmetic

6. ECG reading - requires logical sequence

+ x .

.

1 2 3 4

7. ECG Machine - Modified Galvanometer

8. Recording : produced by vertical movt. of heated Stylus

across paper moving horizontally

9. The principle :

+

Current Electrode +ve Deflection

Electrode Current

- ve Deflection

+

10. ECG paper - Black Background

- Heat sensitive

- Grey substance coated

- Erased by heated stylus

11. ECG paper - moves at a constant speed

- 25 mm per second

- can be increased to

- 50 mm per second

12. ECG paper - has horizontal and vertical lines

- I mm apart

- just as in a graph paper

13. Every 5th Horizontal line - Thicker

14. Every 5th Vertical line - Thicker

15. Every 25th Vertical line - Extended up

16. Measured in horizontal direction

1 small division (S.D.) = 1mm = 0.04 sec

17. 1 Big division (B.D.) = 5mm = 0.20 sec

18. 1 Extended division (E.D.) = 25 mm = 1 sec

- 2 SD = 0.08 sec

- 2 BD = 0.40 sec

- 2 ED = 2.00 sec

19. Measured in vertical direction

Principle : 1 mv of current produces a deflection of 10 sd

20. 1 small division (s.d) of height of wave

is = 0.1 millivolt. (ie, isd = 0.1 mv)

21. However the amplitude or voltage of defections

is expressed in mm of height or depth of waves

r

s

r = 6mm

s = 12mm

CONVENTIONAL 12 LEAD ECG

has three types of leads :

22. Standard Limb Leads I II III

23. Augmented Unipolar Limb Leads aVR aVL aVF

24. Unipolar chest leads V1 V2 V3 V4 V5 V6

II III

++

RL

Earth

LL

27. Positive electrodes placed in LA and LL why ?

Because current moving towards

a + electrodes produces a + deflection.

And that is what we want.

aVR aVL

+-

--

STANDARD LIMB LEADS

25. Recorded by placing (+) electrodes

in Right Arm (RA), Left Arm (LA), Left Leg (LL)

26. Recording ECG with

RA - + LA +

I

1200 III

I 0o

aVF 900

II 600

-300

RA LA

CTW

LL

Neutral Electrode

named

Central Terminal of Wilson

29. Another electrode placed on RA, LA & LL (Named Exploring Electrode)

I + VL

IIIII

+ VF

VR. VL. VF

50 %

30. Disconnecting corresponding leads from CTW Augments current by 50 %

aVR aVL aVF

VR

AUGMENTED UNIPOLAR LIMB LEADS

28. Electrode made by connecting RA, LA&LL through 5000 Ohm resistance

32. Similar exploring electrode placed over the chest at

4 Rt IC space near RSB - V1

4 Lt IC space near LSB - V2

Between V2 and V4 - V3

5 Lt IC space in MCL - V4

Same plane as V4 in AAL - V5

Same plane as V5 in MAL - V6

V1 V2

V3V4

V5 V6

V3R

V4R

33. Rt sided chest leads obtained in place of V3 & V4 on Rt - V3R V4 R

UNIPOLAR CHEST LEADS

31. Similar nutral electrode CTW

Apex AAL MAL

RA LA

CTW

LL

NORMAL WAVE PATTERN

34. Each heart beat represented by

a regular sequence of wave patterns

35. These waves were named by Einthoven

as P.Q.R.S.T and U waves.

36. For convenience these waves can be regrouped

as P wave

QRS complex,

T wave and

u wave

ELECTRICAL CORRELATION

37. P wave - Atrial depolarisation

38. QRS complex - Ventricular depolarisation

39. T wave - Ventricular repolarisation

Atrial repolarisation : some where within - PR- QRS

Too small to be seen.

ABOUT EACH WAVE (Definition)

40. P wave - initial wave of heart beat complex

- upward and convex

41. Q wave - initial negative deflection

following a P wave

42. R wave - initial positive deflection

following a Q wave

or the - first positive

deflection of QRS complex

ABOUT EACH WAVE (Definition) (Contd.)

43. S wave - negative deflection

following R wave

OR - second negative deflection

44. T wave - upward convex wave

following QRS

45. U wave - Small upward convex

wave following T wave

Not always seen.

INTERVALS (Definition)

46. PR interval

measured from beginning of P

to beginning of initial wave of

QRS complex Q,R or QS.

47. QRS duration

measured from beginning of

initial wave of QRS complex to the

end of last wave of QRS complex

48. RR interval

from tallest point of R

to tallest point of next R

LEAD SELECTION

49. All leads need through scrutiny before final interpretation

50. For rhythm assessment - lead II and V1 ( P waves best seen)

51. For Axis assessment I II III a VR aVL aVF

aVR aVL

1200 III

I 0o

aVF 900

II 600

-300-1500

NOW START READING ECG IN 12 MAJOR STEPS

I. STANDARDISATION

52. Standardisation : standard against

standard lead - which other leads are read

53. Normal Standardisation

1mv current - produces deflection of 10 sd.

.

. . Std: 1 mv = 10 sd.

54. Half standard ECG

Reduce deflections to 1/2

.

. . Std: 1 mv = 5 sd.

.

. . To calculate voltage X2

Always look for the label 1/2 V1 1/2 V2 etc.

}

II RATE ( Heart Rate)

55. Calculate the rate : 300/ No BD in RR ; III ly 2 BD - 150

Simple method 3 BD - 100

Look for R falling on Bid Divisions 4 BD - 75

If RR = 1 BD, HR = 300/mt. 5 BD - 60

6 BD - 50

56. For more accurate value

1500/ No of Small divisions

between adjacent RR

57. If rhythm is irregular

Count QRS within 6 sec of ECG paper

Multiply by 10 to get HR in 60 sec.

III RHYTHM

58. Rhythm - is said to be Normal Sinus Rhythm (NSR) if

- HR 60-100/mt. - Each P - QRS - T.

- PR interval -Normal - QRS duration - Normal

59. Normally slight variation during respiration

HR with inspiration with expiration

Sinus Arrhythmia

Exp Insp Exp

60. Abnormal Rhythm

- Arrhythmia

- Study lead II & V1 - (Rhythm Strip)

- P waves best seen in II & V1

Criteria - Difference between shortest & widest RR

should be > 0.12 sec.

IV AXIS:

61. Axis - means electrical axis of heart

Normal

Rt axis deviation

Lt axis deviation

Rt

62. Determination of axis - Crude but simple method

study lead I and III alone

63. I

III(N)

Converge Diverge

(LAD)(RAD)

Lt

Net -ve

V P WAVE

64. P Wave - normally upward convex

- normally inverted in aVR may be in V1

- abnormally inverted in Junctional Rhythm

- replaced by fibrillary waves in AF.

65. P wave - normally not > 2.5 mm in width

- if 3 mm or more in width & notched

- called P mitrale - Left Atrial Enlargement - Mitral Stenosis

66. P wave - normally not > 2.5 mm in height

- if 3 mm or more in height and peaked

- called P. pulmonale - Right Atrial Enlargement - Cor pulmonale

VI PR INTERVAL (PQ)

67. PR Interval - Measure from

Beginning of P wave to

Beginning of QRS complex

Normal Range 0.12 - 0.20 sec ie 3-5 sd.

68. PR Interval - Prolonged

- More than 0.20 sec.

- I0 Heart Block as in

- Rheumatic Carditis.

69. PR Interval - Shorter

- less than 0.12 seconds

- Wolff Parkinson White Syndrome

- Junctional Rhythm

VII Q WAVE

70. Normally. No significant Q in any lead.

may be Small q in III, II, V5 V6

71. Q present & more than .04 sec ie, 1 sd. in width

It is is significant or pathological

It indicates an Electrical Window in myocardium

due to Myocardial Infarction ( AMI).

72. Before saying a Q as pathological make doubly sure

Because you are diagnosing

Transmural Myocardial Infarction

In that case Q will be present in more than one lead

representing the particular wall of heart.

Q .04 sec.

VIII QRS DURATION

73. QRS Duration - measured from

- initial wave of QRS

- to the last wave of QRS

- Normal < 2 sd. 0.08 sec.

74. QRS Duration - Prolonged

- > 2 sd

- ventricular Conduction Defect:

- RBBB or LBBB or VCD

75. QRS Patterns - Numerous

- Vary from lead to lead

- Person to person

IX ST SEGMENT

76. ST Segment - From End of S wave ( J point)

- To beginning of T. wave

Normally - ST same plane as baseline or Isoelectric line

77. ST Segment Elevation

in comparison

to Isoelectric line

78. ST Segment Depression

Pericarditis (Concave) myocardial injury in AMI (Convex)

(Square wave)

(Slanting)

Angina Pectoris Ventricular Strain pattern in LVH or RVH

( J point elevation of 1mm or more from baseline )

Coving ST

X . T WAVE

79. T wave normally upright in all leads except

in AVR and some times in V1

80. T wave tall and peaked

Hyperacute phase of Infarction, Hyperkalemia

81. T wave Symmetrically inverted

in Ischaemia of Myocardium

T wave Asymmetrically inverted

In strain pattern of LVH ( V5 V6) & RVH ( V1)

Symmetrically AssymetricallyPeaked Flat Inverted InvertedBiphasic N

XI R/S IN V1

82. Amplitude of R in V1 ie R/S ratio in V1

Amplitude of S in V1

Normally R in V1 is smaller than S in V1

Therefore R/s Ratio in V1 is <1

83. If R/S ratio in V1 is > 1 ie R is > S in V1

Voltage Criteria for Right ventricular Hypertrophy ( RVH)

Other Criteria for RVH:

QR pattern in V1,ST dep. & T inv in V1, Persistent Deep S in V5 or V6

84. Other conditions where R> S in V1

True Posterior Wall Infarction

Right Bundle Branch Block.

XII SV1 + RV6

85. Add Amplitude of S wave in V1 +

R wave in V6 or V5 whichever is taller

Normal < 35mm

86. If SV1 + RV6 is > 35 mm

in a person above 35 yrs

It forms the voltage criteria for

Left Ventricular Hypertrophy (LVH)

87. Other criteria for LVH are : RV5 or RV6 > 26 mm

R1 + SIII > 26mm ST depression T inversion V5 V6

STAGE OF EVOLUTION OF IHD

88.

ST depression Disappears

during chest pain after chest pain

89.

Ventricluar Tall peaked

Activation time Elevation T wave

90.

Path Q ST Elevation T Inversion

Angina Pectoris

Hyper Acute

Phase of Infarction

Acute

myocardial Infarction

WALL OF INFARCTION

91.

Inferior

Wall

Infarction

92. Anterior

Wall

Infarction

93.

Lateral

Wall

Infarction

AGE OF INTERACT

94. If all changes of Acute MI ( ST , T , path Q)

are present simultaneously: Recent Infarction

95. If ST becomes Isoelectric

but T and Q changes persist: Healing Infarct.

96. If only Q or QS persist

long after chest pain : Old Infarct .

MISCELLANEOUS CONDITIONS

97. Acute Pericarditis : ST elevation in all leads

Concordant ST elevation

98. Hyperkalemia : Tall peaked T Prolonged PR Flat P

Wide QRS Conduction abnormalities

99. Hypokalemia : Flat or inverted T, Depressed ST

Pathological u wave

100. FINAL IMPRESSION - Eg: NORMAL ECG

I. Standardisation 1 mv = 10 sd

II. Heart Rate : 75/mt

III. Rhythm : NSR

IV. Axis : Normal ECG dt 1-11-99

V. P : Normal Normal Sinus Rhythm

VI. PR : 0.16 sec No evidence of IHD

VII. Q wave : Nil pathological No evidence of chamber

VIII. QRS duration : 0. 06 sec enlargement.

IX. ST segment : Isoelectric Imp: Normal ECG

X. T wave : in all leads

XI. R/S V1 : 3 / 6 mm

XII. SV1 + RV6 : 30 mm

100. FINAL IMPRESSION - Eg : ABNORMAL ECG

I. Standardisation : 1 mv = 10 sd

II. Heart Rate : 54/mt

III. Rhythm : Sinus Bradycardia ECG dt 2-1-99

IV. Axis : Left Axis Deviation Sinus Bradycardia

I0 Heart Block

V. P : Wide and notched Acute Inferior Wall

Myocardial Infarction

VI. PR : 0.28 sec

VII. Q wave : path Q in II III aVF Lt Atrial Enlargement

VIII. QRS duration : 0.06 in V1 Lt Ventricular Hypertrophy

IX. ST segment : Elevation II III aVF with strain

Slanting ST in V5 V6

X. T wave : Inverted II III aVF V5 V6

XI. R/S V1 : 3/20 MM

XII. SV1 + RV6 : 20+26 = 46 mm