Electrocardiography: is the recording of the electrical impulses that are generated in the heart. These impulses initiate the contraction of cardiac muscles.

1. ‫اعداد‬
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‫عبيد‬ ‫بندر‬ ‫خميس‬
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‫مصيحب‬ ‫صباح‬ ‫زكي‬
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‫الحسين‬ ‫عبد‬ ‫جبار‬ ‫علي‬
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‫الحسين‬ ‫عبد‬ ‫سعود‬ ‫حسن‬
‫كربالء‬ ‫جامعة‬
‫التمريض‬ ‫كلية‬

2.  Objectives
 • Review the anatomy and physiology of the electrical
conduction of the heart
 • Interpret the term electrocardiography
 • Describe the types of ECG monitoring
 • Interprets the basics of ECG
 • Determine the heart rate from ECG
 • Explain the cardiac rhythm
determination
 • Understand the 12 lead ECG
 • Differentiate the electrode placement
 • Distinguish abnormal ECG from normal ECG

3.  Electrocardiogram ECG
INTRODUCTION
 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“)
 Electrocardiography: is the recording of the electrical impulses
that are generated in the heart. These impulses initiate the
contraction of cardiac muscles.
 It is a transthoracic interpretation of the electrical activity of
the heart over time captured and externally recorded by skin
electrodes.
 The device used to produce this non invasive record is called the
electrocardiograph.
 ECG is the gold standard for the noninvasive diagnosis of cardiac
diseases and may occasionally be the only marker for the presence
of heart disease.

4.  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!!

5.  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.

6. 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.

7. Within the ventricular mass, conduction spreads
somewhat moreslowly, through specialized
tissue called ‘Purkinje fibres’.
Sinoatrial node
AV node
Bundle of His
Bundle Branches
Purkinje fibers

8. SA node Atrium contraction p wave
Purkinje fibers ventricles relaxation T wave
AV node ventricles contraction QRS wave

9.  P wave = atrial depolarisation.
 PR Interval = impulse from atria
to ventricles.
 QRS complex = ventricular
depolarisation.
 ST segment = isoelectric - part
of repolarisation.
 T wave = usually same direction
as QRS – ventricular
repolarisation.
 QT Interval = This interval
spans the onset of depolarisation
to the completion of
repolarization
of the ventricles.

10.  The adjacent figure shows the normal sinus rythem
A normal sinus rythem 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
repolization 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.
•PR interval- beginning of the P wave to the
beginning of the QRS complex
* As depicted in the fig:-

11. •ST segment- connects the QRS complex and the T wave.
•QT interval- the beginning of QRS complex to the end of the T wave
 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
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.
U
U
U

12. myocardial cells are the other pacemaker sites.
When SA node fails, they can initiate impulse at
a slow rate.
Rates Of Pacemakers
1. SA node 60 – 100 bpm 2. Atrial cells 55 – 60 bpm
3. AV node 45 – 50 bpm 4. Bundle of His 40 – 45 bpm
5. Bundle branch 40 – 45 bpm 6. Purkinje cells 35 – 40 bpm
7. Myocardial cells 30 – 35 bpm
 ECG Lead:
 There are twelve leads consisting of six limb leads (I, II,
III, aVR, aVL and aVF)(vertical view)
and six chest leads (V1 to V6)(horzental view).
The limb leads consists of standard bipolar (I, II and III)
and augmented (aVR, aVL and aVF) leads.
The bipolar leads were so named because they record the
difference in electrical voltage between two extremities.

13. 12 conventional leads, physiologically divided into two groups
viz:
Bipolar leads- 3 Standard limb leads
Unipolar leads-3 Augmented limb leads and 6 precordial
chest leads
Bipolar leads : These record the actual
difference in potential across the two
electrodes. There are three standard limb
lead:-
• Lead I Left arm R arm
• Lead II Left foot R arm
• Lead III Left foot L arm
Einthoven's triangle
augmented unipolar
limb Leads by
aVR, aVF, aVL leads

14. Unipolar leads 6 precordial chest leads

15. Placement of Chest leads.
V 1 - 4th intercostal space , right of sternum.
V 2 - 4th ICS left of sternum
V 4 - 5th ICS midclavicular line
V 3 - Midway between V2 and V4
V 5 - 5th ICS anterior axillary line.
V 6 - 5th ICS mid axillary line.
Placement of limb leads:
Right arm (RA)
Left arm (LA)
Right leg (RL)
Left leg (LL)

16. 2004 Anna Story 16
Each ECG lead provides a
different view of the heart

17. Leads of Limb
and Chest

18. Height
=
millivolts
Width = Time
ECG paper consists of horizontal and vertical lines. The
horizontal axis of the ECG strip represents time. Each small
box equals 0.04 second. The ECG strip’s vertical axis
measures amplitude in millimeters

19. Calibration
 1 Small Square = 1 mm (0.1 mV)
 1 Large Square = 5 mm (0.5 mV) Vertical Axis
 2 Large Squares = 10 mm (1 mV)
 1 Small Square = 0.04 sec
 1 Large Square = 0.2 sec Horizontal Axis
 5 Large Squares = 1 sec

23.  Rate Determination (pulse calculation )
 Large Box Method
 Just for Regular rhythms can be quickly determined by
 counting the number of large graph boxes
 between two R waves or P waves . That number is divided
INTO 300 to calculate bpm.
 Ex. Below : - Take tow R wave and calculate large box
between it.
 No. of large box between R waves divided / 300 = pulse
 3 large box / 300 = 100 beat/min

24.  6 Sec Strip ( 30 large box )
 The best method for measuring regular and irregular rates
 with varying R-R intervals is to count the number of R waves
in a 6-sec strip and multiply by (10).This gives the average
number of bpm.
 Every 3 seconds (15 large boxes) is marked by a vertical line.
 Ex. Below
 Take 6 sec = 30 large box
 Calculate R wave in 30 large box = 10 R wave
 R wave no. X 10 = pulse .. 10 X 10 = 100 beat/min
3 sec 3 sec

25.  Small Box Method
 Just for Regular rhythms.
 Sometimes it is necessary to count the number of small
boxes between two R waves for fast heart rates.
 That number is divided into 1500 to calculate bpm.
 Ex. Below
 Take tow R wave and calculate small box between it.
 No. of small box between R waves divided / 1500 = pulse
 1500 / 16 small box = 94 beat/min