2. INTRODUCTION
ECG stands for electrocardiogram: electro =
electrical; cardio = heart; gram = recording.
Therefore, the ECG records electrical activity
of the heart. When the heart beats, the cells
of the heart depolarize. When depolarization
occurs, positively and negatively charged ions
(Na+, Ca2+, K+, and Cl-) move in and out of the
heart cells. This movement of ions creates
electrical changes on the surface of each cell.
3. At any given time, one could imagine that the
myocytes that are depolarizing are causing
microscopic electrical charges at each individual
cell.
Adding up all those microscopic charges, you get a
total electrical charge. It is this total charge that
can be measured from the skin as an ECG. The
“size” of this charge will be determined by how
many microscopic charges are being added up at a
given time.
The position in space of the total charge moves as
the wave of depolarization moves through the
heart. The ECG measures movement of the
electrical charge.
4. 12 lead Ecg: examines the electrical
activity of the heart from 12 points of
view. Only uses 10 electrodes.
Two types of leads – unipolar and bipolar
5. CONTD
• ECG paper divided in to horizontal lines and
vertical lines, large square and small square
• Voltage is represented in the vertical axis of the
ECG paper .
• Each small square is 1 mm in height 1largee square
is 5mm which is equivalent to 0.5mv.
• Time is measure on the horizontal axis .each small
square signifies the passage of 0.04 sec
• Each large square indicate the passage of 0.20
sec.
6. THE ECG PAPER
Horizontally
One small box - 0.04 s
One large box - 0.20 s
Vertically
One large box - 0.5 mV
7. BASIC PRINCIPLES OF ECG
It is the record of electrical impulse generated
in the heart by depolarization and repolarization
of the myocardium.
These impulses are transmitted to the surface
of the body where they are detected and picked
up by the electrodes and measured by
galvanometer (electrocardiograph).
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8. CLINICAL USES
The ECG is a useful tool in the diagnosis of conditions :
♪ MI and other types of CAD such as
angina.
♪ Cardiac dysrhythmias.
♪ Cardiac enlargement.
♪ Electrolyte disturbances (calcium,
potassium, magnesium, and phosphorous).
♪ Inflammatory diseases of the heart.
♪ Effects on the heart by drugs, such as
antiarrhythmics and tricyclic
antidepressants. 6/4/2018 Cardio Diagnostics 8
9. LEAD PLACEMENT
Bipolar limb leads (frontal plane):
Lead I
Lead II
Lead III
Augmented unipolar limb leads (frontal plane):
Lead aVR
Lead aVL
Lead aVF
Unipolar chest leads (horizontal plane):
Leads V1, V2, V3: (Posterior Anterior)
Leads V4, V5, V6:(Right Left, or lateral)
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10. Bipolar limb leads (frontal)
Measure electric potentials of 2 of 3
electrodes
Lead I: from Right arm to left arm (left view
of heart)
Lead II: from Right arm to Left leg (inferior
left view)
Lead III: from Left arm to Left leg (inferior
right view)
13. Augmented Limb Leads (Unipolar)
Use one limb electrode as positive pole
and take average of inputs of the other
2 limb leads
AVR: Upper right side of heart
AVL: Upper left side of heart
AVF: Inferior wall of heart
15. LEAD PLACEMENT
V1: 4th intercostal space to the right of
sternum
V2: 4th intercostal space to the left of
sternum
V3: half way between v2 and V4
V4: 5th intercostal space in the mid-clavicular
line
V5: 5th intercostal space in the anterior axillary
line
V6: 5th intercostal space in the mid axillary line
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18. P WAVE
It is the first positive deflection, smoothly
rounded.
Presence of P wave indicates that the
stimulus began in the S.A. node and
subsequently spreads through both atria
causing atrial contraction.
It has a duration of less than 0.12 seconds
And a height of 2.5mm.
(3 small squares in width and height)6/4/2018 Cardio Diagnostics 18
19. Characteristics of a normal p wave:
The maximal height of the P wave is 2.5
mm in leads II and / or III
The p wave is positive in II and AVF, and
biphasic in V1
The p wave duration is shorter than 0.12
seconds
20. QRS COMPLEX
Q-wave; initial downward deflection
R-wave; a large upward deflection
S-wave; a second downward deflection
It represents the depolarization of
ventricles, time required for the impulse
to spread through ventricles and complete
ventricular contraction.
Normal QRS complex measures 0.08-0.11
sec or less than 3 small squares in width.
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21. P-R INTERVAL
It measures from the beginning of P
wave to the beginning of QRS complex.
It represents the time duration the
wave of contraction passes through the
entire conduction system from AV node
to the purkinje fibres in the
myocardium.
Normally, it measures less than 0.20
seconds
(5 small squares in width)6/4/2018 Cardio Diagnostics 21
22. S-T SEGMENT
It begins at the end of S wave and terminates at the
beginning of T-wave.
It correlates with the period between the
ventricular depolarization and repolarization.
Normally, S-T segment remains on the isoelectric
line.
If the S-T segment is more than 1 mm above or
below the base line, it indicates possible myocardial
ischemia or infarction.
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23. T-WAVE
It represents the electrical recovery of
ventricles (repolarization).
Normally, it appears upright and measures less
than 0.20 seconds in width and not more than
5mm in height.
Flat T waves indicate myocardial ischemia
Inverted T waves indicate myocardial infarction
Unusually tall T waves indicate elevated serum
potassium levels.
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24. U WAVE
It is the small upright wave of low voltage,
sometimes seen following T-wave.
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25. REPORTING OF THE ECG:-
1. heart rate
2. Rhythm
3. PR interval
4. QRS interval
5. QT interval
6. P wave
7. QRS complex
8. STsegment
9. T wave
10. U wave
30. CALCULATING RATE
Interpretation bpm Causes
Normal 60-99
Bradycardia <60 hypothermia, increased
vagal tone (due to vagal stimulation or e.g.
drugs), atheletes (fit people)
hypothyroidism, beta blockade, marked
intracranial hypertension, obstructive
jaundice, and even in uraemia, structural
SA node disease, or ischaemia.
31. Tachycardia >100 Any cause of adrenergic
stimulation (including pain);
thyrotoxicosis; hypovolaemia; vagolytic
drugs (e.g. atropine) anaemia, pregnancy;
vasodilator drugs, including many
hypotensive agents; FEVER, myocarditis
32. RHYTHM
Look at p waves and their relationship to QRS
complexes.
Lead II is commonly used
Regular or irregular?
If in doubt, use a paper strip to map out
consecutive beats and see whether the rate is
the same further along the ECG.
Measure ventricular rhythm by measuring the R-R
interval and atrial rhythm by measuring P-P
interval.
33.
34.
35.
36.
37.
38.
39.
40.
41.
42. CARDIAC AXIS
Electrical impulse that travels towards
the electrode produces an upright
(positive) deflection (of the QRS
complex) relative to the isoelectric
baseline. One that travels away produces
negative deflection. And one that travels
at a right angle to the lead, produces a
biphasic wave.
43.
44. Axis Lead I Lead II Lead III
Normal Positive Positive Positive/Negative
Right axis Negative Positive Positive
Left axis Positive Negative Negative
48. +90 to -30 – Normal
-30 to -90 – left axis deviation
+90 to +180 - Right axis deviation
49.
50.
51.
52. Cardiac Axis Causes
Left axis deviation Normal variation in
pregnancy, obesity; Ascites, abdominal
distention, tumour; left anterior
hemiblock, left ventricular hypertrophy,
Inferior MI
Right axis deviation normal finding in
children and tall thin adults, chronic lung
disease(COPD), left posterior hemiblock,,
anterolateral MI.
54. Normal P- wave
3 small square wide, and 2.5 small
square high.
Always positive in lead I and II in
NSR
Always negative in lead aVR in NSR
Commonly biphasic in lead V1
55. P PULMONALE
TALL PEAKED P WAVE. GENERALLY DUE TO ENLARGED
RIGHT ATRIUM- COMMONLY ASSOCIATED WITH
CONGENITAL HEART DISEASE, TRICUSPID VALVE
DISEASE, PULMONARYHYPERTENSION AND DIFFUSE
LUNG DISEASE
56. BIPHASIC P WAVE
ITS TERMINAL NEGATIVE DEFLECTION MORE
THAN 1 MM DEEP IS AN ECG SIGN OF LEFT
ATRIAL ENLARGEMENT.
57. P MITRALE
WIDE P WAVE, OFTEN BIFID, MAY BE DUE TO
MITRAL STENOSIS OR LEFT ATRIAL
ENLARGEMENT.
58.
59.
60.
61.
62.
63.
64.
65.
66. Left Bundle Branch Block (LBBB)
indirect activation causes left ventricle
contracts later than the right ventricle.
QS or rS complex in V1 - W-shaped
RsR' wave in V6- M-shaped
Mnemonics: WILLIAM
67.
68.
69. Right bundle branch block (RBBB)
indirect activation causes right ventricle
contracts later than the left ventricle
Terminal R wave (rSR’) in V1 - M-
shaped
Slurred S wave in V6 - W-shaped
Mnemonics: MARROW
70.
71.
72.
73.
74.
75.
76. LVH
Hypertension (most common cause)
Aortic stenosis
Aortic regurgitation
Mitral regurgitation
Coarctation of the aorta
Hypertrophic cardiomyopathy