ECG is a three letter acronym for ElectroCardioGraphy. The word is derived from electro(greek for electricity),cardio(greek for heart) and graph(Greek root meaning "to write“) An ECG (electrocardiogram) is a test that records the electrical activity of your heart over time

1. ECG
S.Rekha
Associate professor,
EGSPCOP.

2. ECG
• ECG is a three letter acronym for ElectroCardioGraphy.
• The word is derived from electro(greek for electricity),cardio(greek for
heart) and graph(Greek root meaning "to write“)
• An ECG (electrocardiogram) is a test that records the electrical activity of
your heart over time.
• It is a transthoracic interpretation of the electrical activity of the heart over
time captured and externally recorded by skin electrodes. It's a non-
invasive procedure that helps doctors diagnose and monitor heart
conditions by measuring the electrical signals produced by the heart's
muscle contractions.
• ECG is the gold standard for the noninvasive diagnosis of cardiac diseases

3. INDICATIONS OF ECG
• Gold standard for diagnosis of cardiac
arrhythmias
• Helps detect electrolyte disturbances
(hyper- & hypokalemia)
• Allows for detection of conduction
abnormalities
• Screening tool for ischemic heart disease
during stress tests
• Helpful with non-cardiac diseases (e.g.
pulmonary embolism or hypothermia
• ECG is a diagnostic tool, NOT a
treatment No one is ever cured by an
ECG!!

4. BASIC ELECTROPHYSIOLOGY
PHYSIOLOGICAL PROPERTIES OF
MYOCARDIAL CELL
Automaticity: ability to initiate an impulse
Excitability: ability to respond to a stimulus
Conductivity: ability to transmit an impulse
Contractility: ability to respond with
pumping action
Depolarization and repolarization of a
cardiac cell generates action potential
ECG is the composite representation
of action potential of all cardiac cell.

5. ELECTRICAL CONDUCTION SYSTEM OF THE
HEART
• The electrical discharge for each cardiac cycle normally
starts in a special area of the right atrium called the
‘sinoatrial (SA) node’.
• Depolarization then spreads through the atrial muscle
fibres.
• There is a delay while the depolarization spreads through
another special area in the atrium, the ‘atrioventricular
(AV) node’.
• Thereafter, the electrical discharge travels very rapidly,
down specialized conduction tissue: first a single
pathway, the ‘bundle of His’, which then divides in the
septum between the ventricles into right and left bundle
branches

6. •Within the ventricular mass, conduction
spreads somewhat more slowly, through
specialized tissue called ‘Purkinje fibres’.
Tissue Conduction rate m/s
SA node 0.05
Atrial pathway 1
AV node 0.05
Bundle of his 0.05
Purkinje system 4
Ventricular mass 1

7. CONDUCTION OF THE IMPULSE:
• Normal resting membrane potential=-90mv
• If the potential rises from -90 to 0, then this excites a further rise of
potential, called the action potential.
• The action potential is transmitted throughout the cell and forms the
impulse.
• During the rise of potential, the membrane becomes permeable to
Sodium ions and the potential rises to a positive direction. This
phenomena is called depolarization.
• The Sodium channels close and there is rapid diffusion of K+ ions into
the exterior, reestablishing the resting membrane potential.
• This is called Depolarization is followed by muscle contraction and
repolarization is followed by muscle relaxation

10. NORMAL SINUS RHYTHM
A normal sinus rhythm comprises of the following waves:-
• P waves- denotes atrial depolarization(electrical vector is directed from the
SA node towards the AV node)
• QRS complex- denotes depolarization of ventricles as well as repolarization
of atrium
• T waves- denotes the repolarization (or recovery) of the ventricles.
The interval from the beginning of the QRS complex to the apex of the T
wave is referred to as the absolute refractory period. The last half of the T
wave is referred to as the relative refractory period.
As depicted in the fig:-
•PR interval- beginning of the P wave to the beginning of the QRS complex
•ST segment- connects the QRS complex and the T wave.
•QT interval- the beginning of the QRS complex to the end of the T wave

12. What differentiates a segment from an
interval?
• A segment is a straight line
connecting two waves.
• An interval encompasses at least one
wave plus the connecting straight line

13. J point-
J-point is the point at which the QRS complex meets the ST wave.
Its an isoelectric point and its importance lies in the fact that ST segment elevation is
measured with respect to it
J WAVE AND U WAVE: These are two abnormal waves that may be seen sum time in the
ecg recordings.

14. J wave
also known as camel-hump sign, late delta
wave, hathook junction, hypothermic wave,
prominent J wave ,K wave, H wave or
current of injury positive deflections
occurring at the junction between the QRS
complex and ST segment(j point) observed
in people suffering from hypothermia with a
temperature of less than 32

15. U wave
• Typically small, and by definition,
follows the T wave
• Prominent U waves are most often seen
in hypokalemia, but may be present in
hypercalcemia, thyrotoxicosis

16. RECORDING THE ELECTROCARDIOGRAM
THE E.C.G PAPER
• ECG machines record changes in electrical
activity by drawing a trace on a moving
paper strip.
• The electrocardiograph uses thermal paper,
which is a graph paper & runs normally at
a speed of 25mm/sec
• Time is plotted on the X axis & voltage is
plotted on the Y axis. In X axis, 1 second
is divided into 5 large squares each of
which represents 0.2 sec.

17. • Each large square is further divided
into 5 small squares which represents
0.04 sec.
• The ECG machine is calibrated in
such a way that an increase of voltage
by 1 mVolt should move the stylus
vertically by 1cms

18. ECG PAPER • Fig adjacent shows a callibration graph.
• The calibration signal should be included with every record

19. ELECTROCARDIOGRAPHIC LEADS:
1. Electrocardiographic Leads (ECG or EKG leads) are
specific viewpoints from which the heart’s electrical
activity is recorded.
2. These leads give a multi-dimensional picture of the
heart, helping to diagnose arrhythmias, myocardial
infarctions, and other cardiac conditions.
3. These leads, attached to the body via electrodes,
allow for a graphical representation of the heart's
electrical signals.
4. The standard 12-lead ECG uses 10 electrodes to
create 6 limb leads and 6 precordial (chest) leads,
offering different perspectives of the heart's electrical
activity.

20. There are two main types of leads:
1. Limb Leads
These are placed on the arms and legs and record the
heart’s electrical activity in the frontal plane (vertical slice of the
body).
a. Standard Bipolar Limb Leads (Einthoven’s Triangle)
Lead I: Right arm (-) to Left arm (+)
Lead II: Right arm (-) to Left leg (+)
Lead III: Left arm (-) to Left leg (+)
b. Augmented Unipolar Limb Leads
aVR: Augmented Voltage Right arm
aVL: Augmented Voltage Left arm
aVF: Augmented Voltage Foot (left leg)

22. 2. Precordial (Chest) Leads
These leads record the electrical activity in the
horizontal plane (cross-sectional slice of the chest).
They are unipolar and placed directly on the chest.

23. MAKING A RECORDING:
 Good contact between body surface and electrode is necessary. It
might be essential to shave the chest and apply electro cardio graphic
jelly
 The patient must lie down and relax to prevent muscle tremor
 Connect up the limb electrodes to the correct limb.
 Limb electrodes have marking on them and also they are colour coded
(red –right arm, yellow-left arm, green left leg and black-right leg)
 Calibrate the record with 1mv signal. There shouldn’t be over
damping or underdamping.
 Any metallic object like watch or jewellary should be remove from the
patients body
 4-5 recording of each lead is recorded

24. Interpretation (adults)
Normal: 50 – 100 bpm
Tachycardia: > 100bpm
Bradycardia: < 50bpm

27. Some pathological entities which can be seen on the ECG:
Shortened QT
interval
Hypercalcemia, some drugs, certain genetic abnormalities.
Prolonged QT
interval
Hypocalcemia, some drugs, certain genetic abnormalities.
Elevated ST
segment
Myocardial infraction
Depressed ST
segment
The heart muscles receive insufficient oxygen
Prolonged PQ
intervals
Coronary artery disease, Rheumatic fever and Scar tissue may
be form in the heart.
Flattened or
inverted T Waves
Coronary ischemia, left ventricular hypertrophy, digoxin effect,
some drugs.
Hyper acute T
Waves
Possibly the first manifestation of acute myocardial infarction.
Prominent U Waves Hypokalemia.
Larger P Wave Indicate enlargement of an Atrium, as may occur in mitral
stenosis in which blood back up in to the left atrium.
Enlarge Q Wave Indicates myocardium infrection.
Enlarge R Wave Indicates enlarged ventricles

29. THANK U