The document provides an overview of electrocardiography (ECG). It discusses the history of ECG development. It then covers how to perform an ECG, how an ECG works by detecting electrical changes during heartbeats, ECG paper calibration, the 12 leads, and how to interpret various ECG components like rate, rhythm, axes, waves, intervals, and segments. Key points about normal ECG readings are also presented along with 10 interpretation rules.

2. Presented by:
‫فیصل‬ ‫محمد‬
‫معاون‬‫ین‬:‫نزیر،وسیم‬ ‫،جنید‬ ‫اختر‬ ‫دانش‬‫احمد‬
P.G Scholars
 DEPARTMENT OF ILMUL JARAHAT
 NATIONAL INSTITUTE OF UNANI MEDICINE, KOTTIGEPALYA, MAGADI
MAIN ROAD.
 BANGALORE-91.

3. 1. History
2. What is an ECG?
3. HOW TO DO ELECTROCARDIOGRAPHY
4. How does an ECG work?
5. ECG Paper
6. Calibration of ECG
7. LEADS
8. Rate
9. Rhythm
10.Cardiac Axis
11.P – wave
12.PR - interval
13.QRS Complex
14.ST Segment
15.QT interval (Include T and U wave)

4. • 1842- Italian scientist Carlo Matteucci realizes that
electricity is associated with the heart beat
• 1876- Irish scientist Marey analyzes the electric pattern of
frog’s heart
• 1895 - William Einthoven , credited for the invention of
EKG
• 1906 - using the string electrometer EKG,
William Einthoven diagnoses some heart problems

5. • 1924 - the noble prize for physiology or medicine is
given to William Einthoven for his work on EKG
• 1938 -AHA and Cardiac society of great Britan
defined and position of chest leads
• 1942- Goldberger increased Wilson’s Unipolar lead
voltage by 50% and made Augmented leads
• 2005- successful reduction in time of onset of chest
pain and PTCA by wireless transmission of ECG on
his PDA.

7. MODERN ECG INSTRUMENT

8. It can provide evidence to support a
diagnosis, but remember…..
LOOK AT THE PATIENT NOT JUST THE
PAPER

9. •The electrocardiogram (ECG) is a representation
of the electrical events of the cardiac cycle.
•Each event has a distinctive waveform
•the study of waveform can lead to greater insight into a
patient’s cardiac pathophysiology.

10. •Chamber hypertrophy
•Arrhythmias
•IHD
•Pericarditis
•Electrolyte disturbances (i.e. hyperkalemia,
hypokalemia)
•Drug toxicity (i.e. digoxin and drugs which prolong the
QT interval)

11. 1. Place the patient in a position. If
the patient cannot tolerate being
flat, you can do the ECG in a more
upright position.
2. Instruct the patient to place their
arms down by their side and to
relax their shoulders.
3. Make sure the patient's legs are
uncrossed.
4. Remove any electrical devices, such
as cell phones, away from the
patient as they may interfere with
the machine.
5. If you're getting artifact in the limb
leads, try having the patient sit on
top of their hands.
6. Causes of artifact: patient
movement, loose/defective
electrodes/apparatus, improper
grounding.
HOW TO DO ELECTROCARDIOGRAPHY
An ECG with artifacts.
Patient, supine position

12. The ECG works mostly by detecting and
amplifying the tiny electrical changes on the
skin that are caused when the heart muscle
"depolarizes" during each heart beat.
Simply Electrical stimulation through the atria and ventricles--
----depolarization
Return to resting state after stimulation (depolarization) is
called repolarization.

14. ▪ P wave—atrial depolarization (stimulation)
▪ QRS complex—ventricular depolarization (stimulation)
▪ ST segment, T wave, and U wave—ventricular
repolarization (recovery)

15. • Horizontally
– One small box - 0.04 s
– One large box - 0.20 s
• Vertically
– One large box - 0.5 Mv
– One page of ECG - 10 sec

16. The electrocardiograph must be properly calibrated so
that a 1-mV signal produces a 10-mm deflection.
ECG paper (25 mm/sec, 10 mm/mV).
A, Electrocardiograph set at normal standardization. B, One half standardization.
C, Two times normal standardization.

17. ECG illustrating the 12 leads. The leads can be subdivided
into two groups:
The six limb(extremity) leads
And the six chest (precordial) leads
The six limb leads—I, II, III, aVR, aVL, and
They can be further divided into two subgroups
Three standard “bipolar” limb leads (I, II, and III), and three
augmented “unipolar” limb leads
(aVR, aVL, and aVF).

18. Lead I, for example, records the difference in voltage
between the left arm (LA) and right arm (RA) electrodes:
Lead I = LA – RA
Lead II records the difference between the left leg (LL) and
right arm (RA) electrodes:
Lead II = LL – RA
Lead III records the difference between the left leg (LL) and
left arm (LA) electrodes:
Lead III = LL – LA

19. Einthoven's triangle
Lead I + Lead III = Lead II
I =LA-RA
III=LL-LA
I+III=LL-RA=II
Einthoven’s equation

20. A, Einthoven's triangle.
B, The triangle is converted to a triaxial diagram by shifting leads I,
II, and III so that they intersect at a common point.

21. Nine leads have been added to the original three “bipolar” extremity
leads.
In the 1930s, Dr. Frank N. Wilson and his colleagues at the University of
Michigan invented the “unipolar” limb leads and also introduced the six
“unipolar” chest leads, V1 through V6.
A short time later, Dr. Emanuel Goldberger invented the three
augmented unipolar limb leads: aVR, aVL, and aVF.
The abbreviation a refers to augmented; V tovoltage; R, L, and F to right
arm, left arm, and left foot (leg), respectively.
Today 12 leads are routinely employed, consisting of the six limb leads
(I, II, III, aVR, aVL, and aVF) and the six precordial leads (V1 to V6).

22. aVR + aVL + aVF = 0

30. ECGINTERPRETATION
The More You See, The More You Know

31. Rate
Rhythm
Cardiac Axis
P – wave
PR - interval
QRS Complex
ST Segment
QT interval (Include T and U
wave)
Other ECG signs

32. 300
the number of BIG SQUARE between R-R interval
Rate =
As a general interpretation, look at lead II at the bottom part of the
ECG strip. This lead is the rhythm strip which shows the rhythm for
the whole time the ECG is recorded. Look at the number of square
between one R-R interval. To calculate rate, use any of the following
formulas:
1500
the number of SMALL SQUARE between R-R interval
OR
Rate =

33. 300
Rate =
For example:
3
1500
15
Rate =or
Rate = 100 beats per minute

34. If you think that the rhythm is not regular, count the number of electrical beats in a 6-
second strip and multiply that number by 10.(Note that some ECG strips have 3 seconds
and 6 seconds marks) Example below:
1 2 3 4 5 6 7 8
= (Number of waves in 6-second strips) x 10
= 8 x 10
= 80 bpm
Rate
There are 8 waves in this 6-seconds strip.

35. You can also count the number of beats on any one row over the ten-second strip (the
whole lenght) and multiply by 6. Example:
= (Number of waves in 10-second strips) x 6
= 13 x 6
= 78 bpm
Rate

36. 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.

37. ECG rhythm characterized by a usual rate of anywhere between 60-99 bpm, every P
wave must be followed by a QRS and every QRS is preceded by P wave. Normal
duration of PR interval is 3-5 small squares. The P wave is upright in leads I and II
Normal Sinus Rhythm

38. Sinus Bradycardia
RHYTHM
Rate < 60bpm, otherwise normal

39. RHYTHM
Sinus Tachycardia
Rate >100bpm, otherwise, normal

40. RHYTHM
Atrial Fibrillation
A-fib is the most common cardiac arrhythmia involving atria.
Rate= ~150bpm, irregularly irregular, baseline irregularity, no visible p waves, QRS
occur irregularly with its length usually < 0.12s

41. RHYTHM
Ventricular Fibrillation
A severely abnormal heart rhythm (arrhythmia) that can be life-threatening.
Emergency- requires Basic Life Support
Rate cannot be discerned, rhythm unorganized

42. RHYTHM
Ventricular tachycardia
fast heart rhythm, that originates in one of the ventricles- potentially life-threatening
arrhythmia because it may lead to ventricular fibrillation, asystole, and sudden death.
Rate=100-250bpm

43. 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.
The cardiac axis refers to the general direction of the heart's depolarization
wavefront (or mean electrical vector) in the frontal plane. With a healthy conducting
system the cardiac axis is related to where the major muscle bulk of the heart lies.

44. The normal QRS axis should be between - 30 and +90 degrees.
Left axis deviation is defined as the major QRS vector falling between -30 and -90
degrees.
Right axis deviation occurs with the QRS axis is between +90 and +180 degrees.
Indeterminate axis is between +/- 180 and -90 degrees.

45. CARDIAC AXIS
Axis Lead I Lead II Lead III
Normal Positive Positive Positive/Negative
Right axis
deviation
Negative Positive Positive
Left axis
deviation
Positive Negative Negative
To determine cardiac axis look at QRS complexes of lead , II, III.
Remember, positive(upgoing) QRS omplex means the impulse travels towards the
lead. Negative means moving away.

46. Positive
Positive
Positive
Normal Axis Deviation
CARDIAC AXIS

47. Positive
Negative
Negative
Left Axis Deviation
CARDIAC AXIS

48. Negative
Positive
Positive
Right Axis Deviation
CARDIAC AXIS

49. 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.
North West emphysema, hyperkalaemia. lead transposition,
artificial cardiac pacing, ventricular tachycardia
CARDIAC AXIS

50. 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
P -WAVE

51. P -WAVE
P pulmonale
Tall peaked P wave. Generally due to enlarged
right atrium- commonly associated with congenital
heart disease, tricuspid valve disease, pulmonary
hypertension and diffuse lung disease.
Biphasic P wave
Its terminal negative deflection more than 40 ms
wide and more than 1 mm deep is an ECG sign of
left atrial enlargement.
P mitrale
Wide P wave, often bifid, may be due to mitral
stenosis or left atrial enlargement.

52. PR INTERVAL
NORMAL PR INTERVAL
PR-Interval 3-5 small square (120-200ms)
(start of P to start of Q)

53. PR-INTERVAL
First degree heart block
P wave precedes QRS complex but P-R intervals prolong (>5 small squares) and
remain constant from beat to beat

54. Second degree heart block
1. Mobitz Type I or Wenckenbach
Runs in cycle, first P-R interval is often normal. With successive beat, P-R interval
lengthens until there will be a P wave with no following QRS complex.
The block is at AV node, often transient, maybe asymptomatic
PR-INTERVAL

55. Second degree heart block
2. Mobitz Type 2
P-R interval is constant, duration is normal/prolonged. Periodically, no conduction
between atria and ventricles- producing a p wave with no associated QRS complex.
(blocked p wave).
The block is most often below AV node, at bundle of His or BB,
May progress to third degree heart block
PR-INTERVAL

56. Third degree heart block (Complete heart block)
No relationship between P waves and QRS complexes
An accessory pacemaker in the lower chambers will typically activate the
ventricles- escape rhythm.
Atrial rate= 60-100bpm. Ventricular rate based on site of escape pacemaker.
Atrial and ventricular rhythm both are regular.
PR-INTERVAL

57. QRS complex< 3 small square (0.06 - 0.10 sec)
QRS COMPLEX

58. Normal duration- 0.06 - 0.10 sec (upto 3 small squares)
Depth of the S wave must not exceed 30 mm.
Nonpathological Q waves may present in I, III, aVL, V5, and
V6.

59. The R wave must grow from V1 to at least V4
The S wave must grow from V1 to at least V3
and disappear in V6

60. • ST Segment is flat (isoelectric)
• Elevation or depression of ST segment by 1 mm or
more is abnormal.
• “J” (Junction) point is the point between QRS and ST
segment
• S in V1 or V2 + R in V5 or V6 should be less than 35
mm.
• V1 R/S ratio or V6 S/R ratio should be less than1mm.

61. • Normal T wave is asymmetrical, first half having
a gradual slope than the second
• Should be at least 1/8 but less than 2/3 of the
amplitude of the R
• T wave amplitude rarely exceeds 10 mm.
• Abnormal T waves are symmetrical, tall,
peaked, biphasic or inverted.

63. 1. Total duration of Depolarization and Repolarization.
2. QT interval decreases when heart rate increases.
3. For HR = 70 bpm, QT<0.40 sec.
4. QT interval should be 0.35 0.45 s,
5. Should not be more than half of the interval between
adjacent R waves (RR interval).

65. • U wave related to depolarizations which follow
repolarization.
• U waves are small, round, symmetrical and positive in lead
II, with amplitude < 2 mm
• U wave direction is the same as T wave
• More prominent at slow heart rates

66. RULE 1
PR interval should be 120 to 200 milliseconds
or 3 to 5 little squares

67. RULE 2
The width of the QRS complex should not exceed
110 ms, less than 3 little squares

68. RULE 3
The QRS complex should be dominantly
upright in leads I and II

69. RULE 4
QRS and T waves tend to have the same
general direction in the limb leads

70. RULE 5
All waves are negative in lead aVR

71. RULE 6
The R wave must grow from V1 to at least V4
The S wave must grow from V1 to at least V3
and disappear in V6

72. RULE 7
The ST segment should start isoelectric
except in V1 and V2 where it may be elevated

73. RULE 8
The P waves should be upright in I, II, and V2 to
V6.

74. RULE 9
There should be no Q wave or only a small q less than
0.04 seconds in width in I, II, V2 to V6

75. RULE 10
The T wave must be upright in I, II, V2 to V6