ECG IN 100 STEPS
By
Dr. S. Aswini Kumar MD
WHAT IS ECG ?
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
ECG READING
4. ECG reading - not a Bali-kera-mala
5. ECG reading - simple arithmetic
6. ECG reading - requires logical sequence
+ x ..
1 2 3 4
ECG MACHINE
7. ECG Machine - Modified Galvanometer
8. Recording : produced by vertical movt. of heated Stylusacross paper moving horizontally
9. The principle :
+
Current Electrode +ve Deflection
Electrode Current
- ve Deflection
+
ECG PAPER
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
THICKNESS OF LINES
13. Every 5th Horizontal line - Thicker
14. Every 5th Vertical line - Thicker
15. Every 25th Vertical line - Extended up
DURATION
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
AMPLITUDE
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
AUGMENTED UNIPOLAR LIMB LEADS
28. Electrode made by connecting RA, LA&LL through 5000 Ohm resistance
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
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 V
3 V4 V
5V6
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
P Q RS
T U
P QRS T U
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.
T
QRS
P
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
P Q
P
R
P
Q
R
P
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.
R
QRS
OR
QS
R
T
U T
S
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
R
P
R
Q
P P QS
Q S
P RR
PP
SS
Q S
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 ArrhythmiaExp 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
P Q
P Q
P
Q
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
rR
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
J
IEL
Pericarditis (Concave) myocardial injury in AMI (Convex)
(Square wave)
(Slanting)
Q S
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)
T
Symmetrically AssymetricallyN Peaked Flat Inverted InvertedBiphasic
R T
R
R T
R
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.
r 6
s 13
rR’
s
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 Vetricular Hypertrophy (LVH)
87. Other criteria for LVH are : RV5 or RV6 > 26 mm
R1 + SIII > 26mm ST depression T inversion V5 V6
+
15
V6V1 10
+
25
V6
V1
20
R
STAGE OF EVOLUTION OF IHD
88.
S TST depression Disappears during chest pain after chest pain
89.
Ventricluar ST Tall peaked Activation time Elevation T wave
90.
Path Q ST Elevation T Inversion
T
Angina Pectoris
Hyper Acute
Phase of Infarction
Acute
myocardial Infarction ST
QT
WALL OF INFARCTION
91.
Inferior Wall
Infarction
92. Anterior
WallInfarction
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 .
QT
ST
Q T
Q QS
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
Thank You
And…
We thank the author for the valuable contribution!