1. Presenting The Topic : ECG
Q. How can we record ECG of a heart?
Q. How is an ECG performed?
Q. What Processes are involved in taking an ECG?
Q. What are the diseases that we can detect through ECG?
Q. What are the benefits of ECG?
Q. Is an ECG dangerous?
2. ECG is the abbreviation of Electrocardiogram.
ECG is also called EKG (Elektrokardiogram) in USA.
The electrical activity of heart was first recorded by Waller in
1887 with a capillary electrometer.
3. The Electrocardiogram (ECG) is a record of the electrical potential changes
that occur in the heart due to the passage of the cardiac impulse during the
cardiac cycle and recorded from the surface of the body.
It is the simple way of diagnosing heart conditions.
The Electrocardiogram (ECG)
4. In an ECG test, the electrical impulses made while the heart is beating are recorded
and usually shown on a piece of paper. This is known as electrocardiograph.
The instrument used to record the ECG is called Electrocardiograph.
5. It records any problem with the heart’s rhythm, and the conduction of the
Einthoven, who made extensive studies, recording the ECG with a string
that led to the development of electrocardiography as a modern technique.
Einthoven was awarded Nobel Prize in 1924-for his discovery of mechanism
6. An ECG is taken while the patient is resting.
But if there’s concern that a patient’s symptoms may be caused by coronary
Then the test is done while the patient is on an exercise bike or treadmill.
7. Electrodes will be attached to select locations of the skin on the arms, legs and
Areas such as the chest where the electrodes will be placed may need to be
First, the skin is cleaned.
The test is completely painless and takes less than a minute to perform once the
leads are in position.
After the test, the electrodes are removed.
The doctor will review the paper print-out of the ECG.
8. How is it done?
Small metal electrodes are stuck on to your arms, legs and
chest. Wires from the electrodes are connected to the ECG
machine. The machine detects and amplifies the electrical
impulses that occur at each heartbeat and records them on
to a paper or computer. A few heartbeats are recorded from
different sets of electrodes. The test takes about five
minutes to do.
10. The ECG shows five waves.
These waves are designated from left to right with letters P,Q,R,S and T.
P wave: The sequential activation (depolarization) of the right and left atria
QRS complex: Right and left ventricular depolarization (normally the ventricles
are activated simultaneously)
ST-T wave: Ventricular repolarization
U wave: Origin for this wave is not clear - but probably represents "after
depolarizations" in the ventricles.
P, R and T are normally upward or positive waves .Where as Q and S are downward
or negative waves in the standard bipolar limb lead.A 6th wave, the ‘U’wave is
11. ECG Intervals
1.PR interval: Time interval from onset of atrial depolarization (P wave) to
onset of ventricular depolarization (QRS complex).
2.QRS duration: Duration of ventricular muscle depolarization.
3.QT interval: Duration of ventricular depolarization and repolarization.
4.RR interval: Duration of ventricular cardiac cycle (an indicator of
5.PP interval: Duration of atrial cycle (an indicator of atrial rate).
13. The first electrical event is the P wave.
P wave is the atrial wave, auricular complex.
P wave is due to the spread of depolarization in the atria.
Its duration is 0.1 sec. Its amplitude is about 0.1 to 0.3 mv.
The P wave is a guide to atrial activity.
14. Q , R and S waves also called QRS complex.
The QRS complex which corresponds to ventricular depolarization.
Q wave is a small negative downward deflection and represents septal
R is a prominent positive wave.
S is a small negative wave.
R and S are due to depolarization of the ventricular muscle.
The duration of QRS complex is about 0.08 sec.
The amplitude is variable, the average R wave is about 1 mv.
Alteration in the QRS complex gives valuable diagnostic information.
15. T wave is a positive wave ocurring after the S wave.
It is due to ventricular repolarization.
It is a broad wave of variable duration and of low amplitude.
The average duration is about 0.27 sec. and amplitude is 0.15 to 0.5 mv.
This repolarization wave is not in opposite direction to the depolarization wave
because repolarization does not follow the same pattern as depolarization.
QRS and T are together referred to as Ventricular Complex.
16. Sometimes a positive U wave may be seen after to T wave.
Its causation is uncertain, but it may be due to slow
repolarization of the papillary muscles.
17. Recording the ECG by placing electrodes directly on the cardiac muscle,
Instead, the ECG is recorded by placing electrodes at different points on the
Measuring voltage differences between these points with the aid of an
Any particular position of a pair of electrodes on the body surface will detect a
particular portion of the current flow during depolarization and repolarization.
18. Electrodes are connected by long cables to the ECG machine.
The skin electrodes are placed on certain specific parts of the body surface
for recording ECG.
The surface over which the electrode is placed is smeared with a jelly (special
cream) or cloth soaked in saline.
19. There are two main types of ECG.
1. Standard Bipolar Leads (3 leads).
2. Unipolar Leads. There are two types of unipolar leads.
1. Augmented limb leads (3 leads).
2. The chest (Precordial) leads (6 leads).
20. There are 12 ECG leads.
The 12-lead ECG provides spatial information about the heart's
electrical activity in 3 approximately directions:
Right ⇔ Left
Superior ⇔ Inferior
Anterior ⇔ Posterior
21. 12 LEADS of ECG
Bipolar limb leads (frontal plane):
Lead I: RA (-) to LA (+) (Right Left, or lateral)
Lead II: RA (-) to LL (+) (Superior Inferior)
Lead III: LA (-) to LL (+) (Superior Inferior)
Augmented unipolar limb leads (frontal plane):
Lead aVR: RA (+) to [LA & LL] (-) (Rightward)
Lead aVL: LA (+) to [RA & LL] (-) (Leftward)
Lead aVF: LL (+) to [RA & LA] (-) (Inferior)
Unipolar (+) chest leads (horizontal plane):
Leads V1, V2, V3: (Posterior Anterior)
Leads V4, V5, V6:(Right Left, or lateral)
22. Lead 1—Right Arm (RA) to negative terminal of amplifier and left
Arm (LA) to positive terminal of amplifier.
With this placement of electrodes, the amplifier records the
component of excitation spreading along an axis between the
right and left sides of the heart.
23. Lead 2—RA to the negative terminal and Left leg (Foot-
LF) to positive terminal.
So that the component of excitation moving from the right
upper portion of the heart to the tip of the ventricles is
24. Lead 3—LA to negative and left leg to positive terminal.
This lead records the component of excitation along an
axis between the left atrium and the tip of the ventricles.
The electrodes over the limbs—connected to the terminals—to obtain
upward deflections in all the three leads.
When the region over the negative electrode is electronegative compared to
the region over the positive electrode, the record is positive and the
deflection is upward.
Bipolar chest leads are no longer used.
They used to be recorded by placing one electrode on a limb.
26. VR, VL, VF are called augmented limb leads.
The voltage that can be recorded from the two arms and the left ankle,
with a unipolar electrode can be increased using the augmented limb leads.
27. Lead aVR
is recorded from the right arm with the reference electrode formed by adding
the signals from left arm and left ankle.
is formed by recording from the left arm with the reference electrode formed
by adding the signals from right arm and left ankle.
is formed by recording the signal from the left ankle with the reference
electrode formed by adding the signals from the two arms.
In these leads, the active electrode is placed on one limb.
Only two limbs are connected to the –Ve terminal through the resistance.
In other words, the electrode of the central terminal to the limb on which
the active electrode is placed is disconnected.
When this is done, the amplitude of the tracing is 1 and ½ times—obtained
without any change in the configuration of the tracing. Since the amplitude
is greater, it is called Augmented Unipolar Limb Leads.
30. When the ECG is recorded using the unipolar chest leads(The active
electrode is placed on six positions on the precordium).
These positions are known as leads V1, V2,V3,V4,V5 and V6.
31. V1: right 4th intercostal space
V2: left 4th intercostal space
V3: halfway between V2 and V4
V4: left 5th intercostal space, mid-
V5: horizontal to V4, anterior axillary
V6: horizontal to V5, mid-axillary line
32. The information obtained from an electrocardiogram can be used to
discover different types of heart disease.
It is a good idea to have an ECG in the case of symptoms such as dyspnea
(difficulty in breathing), chest pain (angina),fainting , palpitations or when
someone can feel that their own heart beat is abnormal.
An ECG can be used to assess if the patient has had a heart attack or
evidence of a previous heart attack.
An ECG can be used to monitor the effect of medicines used for coronary
An ECG reveals rhythm problems such as the cause of a slow or fast heart
33. The underlying rate and rhythm mechanism of the heart.
The orientation of the heart (how it is placed) in the chest cavity.
Evidence of increased thickness (hypertrophy) of the heart muscle.
Evidence of damage to the various parts of the heart muscle.
Evidence of acutely impaired blood flow to the heart muscle.
Patterns of abnormal electric activity
34. 1.Especially Myocardial Ischaemia Heart Disease and Infarction
3.Tachyarrhythmias or Tachycardias
4.Bradyarrhythmias (Bradycardia Sinus Bradycardia And Sick Sinus Syndrome)
5.Heart Block (Atrio Ventricular Block)
6.Right and Left Ventricular Hypertrophy
7.Hypertrophy of Atria
8.Wolff-Parkinson-White (WPW) Syndrome
9.Hyperkalaemia and Hypokalaemia
10.Ambulatory 24-hour ECG Recording (Holter Monitoring)
35. A cardiac infarction is another condition which results in dead tissue in a part of
the heart muscle, and therefore the electric signal cannot travel through that
A left or right bundle branch block delays the electric wave from spreading to the
left or right part of the heart.
Sometimes these conditions affect the heart's ability to pump blood.
The ECG changes are best seen in the lead which faces the infarct.
37. Disturbances in heart rate and rhythm may be due to abnormalities in:
a) Impulse formation or
b) Impulse conduction.
Normal heartbeats that pump blood rely on regular electrical
Irregular electrical impulses, termed arrhythmias, can alter, reduce, or
even stop the heart's ability to pump blood.
If a person notices their heartbeat is abnormal (fast, slow, or
irregular), they should seek medical care if the arrhythmia persists or
causes chest pain.
38. Increase in heart rate (over 100/min) called Tachycardias or Tachyarrhythmias
1.Premature contractions or Extra-systol
39. 1.Premature contractions or Extra-systol
QRS may be abnormal.
The Patient may have palpitations.
Paroxysms of very rapid heart rate (150/min).Duration may vary from
few seconds to a few minutes.Arise in the ventricle.
There may be abnormal or inverted P waves with some impulses to
ventricle blocked.Patient may have palpitations.
40. The atria beat very rapidly about 300/min (250 to 350).
The P wave is abnormal also called Flutter or F waves.
Atrial fibrillation is a heart rhythm abnormality caused by a problem with the heart's
electrical system. Normally, the heart's electricity flows from the top chambers (atria) to
the bottom chambers (ventricles), causing the normal contraction . In atrial fibrillation the
electrical flow is chaotic causing the heartbeat to become irregular.
Atria beat very rapidly (400-500/min).
The QRS appears normal but irregular.
The pulse is also very irregular.
The ECG shows no P waves .
42. The ventricles contract Irregularly and ineffectively.
The ECG shows pattern of low voltage irregular waves.
The fibrillating ventricle is unable to pump blood and circulation will cease
and the condition is rapidly fatal.
It is a medical emergency
The patient must be promptly attended to and electrically defibrillated.
43. Reduction in heart rate ( less than 60/min) and called Bradycardias or
Sino aterial block, the impulses are not conducted from the sinus.
There is a sinus arrest in which sinus does not set up impulses for long
The condition is associated with fatigue, attacks of dizziness and
The ECG shows long intervals between P waves.
44. A heart attack occurs when a coronary artery becomes blocked (usually in a
coronary artery by a blood clot) resulting in loss of the blood supply to an
area of heart tissue.
Loss of the blood supply can quickly damage and kill heart tissue,
Quick treatments in the emergency have reduced deaths from heart
46. There are three Degrees of Heart Block.
1. First Degree Heart Block
2. Second Degree Heart Block
3. Third Degree Heart Block
47. 2.Second Degree Heart Block
In this form of partial heart block, some impulses are strong enough to pass
through to the ventricle.
48. 3. Third Degree Heart Block
In this disorder, no atrial impulse passes to the ventricle.
The atrial and ventricular contractions are completely dissociated
with the atria beating at their own normal rhythm,
and the ventricles at their much slower rate (30-40/min) and is
called the Idioventricular rhythm.
49. 1.Chest pain
2.Pain that may spread to the back, arms, neck, and jaw
3.Shortness of breath
5.Rapid or irregular heartbeats
6.Other symptoms such as weakness, anxiety, indigestion, and heartburn
50. The ventricle is hypertrophied when it has to pump blood against
The right ventricle is hypertrophied in pulmonary stenosis and
The left ventricle is hypertrophied in aortic stenosis and systemic
ECG shows a deviation of the mean electrical axis towards the
There may be a widening of the QRS with a slight increase in voltage.
51. Approximately one million Americans suffer a heart
attack each year.
Four hundred thousand of them die as a result of their
52. Right atrial hypertrophy occurs in tricuspid stenosis and left atrial
hypertrophy occurs in mitral stenosis.
Tall P waves are seen in right atrial hypertrophy as the voltage in the
hypertrophied right atrium is high.
53. It is a condition in which P—R interval is reduced to less than 0.12
This is due to the presence of an abnormal bypass conducting
pathway with a high conduction rate,
between the atria and ventricles
54. Both Hyperkalaemia and Hypokalaemia affect heart’s action and
produce ECG changes.
The T waves are tall and peaked.
The T waves are flat or inverted and U wave is prominent.
55. As electrocardiographic device, invented by Hotler can be strapped to the
Can continuously record ECGs as the patient moves about and performs his
day to day activities.
Records are usually taken over a 24-hour period.
This helps to detect transient episodes of arrhythmias or ischaemia.
Since 100,000 ECG complexes are recorded over a 24-hour period.
56. ECG can also be used to determine the electrical axis of the heart as a
Which can itself give information about certain pathological cardiac
Such as ventricular hypertrophy.
57. When the patient is at rest, it is completely harmless.
If an exercise test is performed, the patient may get chest
pains that will resolve after the exercise is stopped.
If necessary, the test will be discontinued at an appropriate
time such as in the case of chest pain, changes on the ECG, a
drop in blood pressure or simply when the patient achieves
their target heart rate.