RAMAPRASAD S ASSOCIATE PROFESSOR MSN

1. Electrocardiography

2. Definition
It is defined as graphical representation of the electrical potentials
generated in the heart in a graphical paper. It is a graphical recording of
electrical activity of the heart. ECG plays a vital role in diagnosis of
various heart diseases and changes in the heart conductive system.

3. Uses of ECG
• Accurate Recording of cardiac activities
• Diagnoses various heart diseases.
• Helps in detection of electrolyte imbalances

4. ECG Sheet

5. • The ECG recorded in the Graph papers which are composed of small
squares in light lines and large squares in dark lines.
• The dimension of the small square is (1 mm X 1mm) and large square
measures about (5 mm X 5mm).
• The amplitude was measured by horizontal line and vertical line
represents time.
• 1 small square = 1mm in size and duration is 0.04 second
• 1 large square= 5 mm in size and duration is 0.2 second
• i,e, 0.04 X 5=0.2 second

6. Normal ECG Waves

9. Waves P,Q,R,S,T,U
Positive
Negative
both
Complexes QRS
Segment
P-Q
S-T
T-P
Duration between a wave
or complex
Interval
P-R
Q-T
R-R
Two point in ECG includes
wave or complex

10. Wave Clinical significance Duration of wave
P wave Atrial depolarization 0.12 sec
QRS complex Ventricular depolarization 0.12 sec
P-R interval Impulse Time to reach ventricles 0.20 sec
S-T segment
Completion of ventricular
depolarization
0.20 sec
T wave
Complete electrical recovery of
ventricles ()ventricular repolarization
0.20 sec

11. Component Description
Rate
Atrial rate
Identify the P wave count the number of small squares
between two P wave and divide by 1500 (shows atrial
rate)
Ventricular rate
Identify the R wave between two QRS complex count
the number of small squares between two R wave and
divide by 1500 (shows Ventricular rate)
Rhythm
Atrial rhythm Measure the distance between two P waves
Ventricular
rhythm
Difference more than 0.12 sec in R-R interval it is
irregular

12. Conduction
P-R interval
Count small square from beginning of P
wave to Beginning of QRS complex.
Multiply by 0.04 sec
QRS duration
Count small square from beginning of Q
wave to Beginning of ST segment and
Multiply by 0.04 sec
Location
P wave Look at all P wave for upright and Inverted
QRS complex Check for M shaped
S-T segment
Normally flat, S-T segment id elevated it
indicates MI
T wave
Should be same size and shape like QRS
complex

13. What To Look In ECG
Components Look for
Heart rate Normal, bradycardia and tachycardia
Cardiac rhythm Regular or irregular
P wave
Shape, duration, connection and relation with QRS
complex
P-R interval Time
QRS complex Time and R-R interval
S-T segment Elevation and depression
T wave Tall, flat and inverted

15. ECG leads

16. Leads Location
V1 4th ICS at right sternum
V2 4th ICS at left sternum
V3 Between V2-V4
V4 5th ICS in midclavicular line
V5 5th ICS anterior axillary line
V6 5th ICS at mid axillary line

17. ECG leads
Standard ECG consists of 12 leads monitoring, among
those 3 are bipolar, 3 are unipolar and 6 are chest leads.
Leads I, II, III are bipolar leads, leads aVR, aVL, aVF are
unipolar leads and V1-V6 are chest leads.