Electrocardiography (ECG)
Definition:
It is the graphical representation of the normal electrical activity of the
heart.
The ECG is used to assess cardiac rhythm and conduction
P-wave:
Due to atrial depolarization.(activation/systole).
Q-wave:
if the first deflection is downward,it is called Q-wave.
R-wave:
any upward deflection is called R-wave.
S-wave:
Any Downward deflection after R wave is called S-wave, but below the baseline .
T-wave:
due to ventricular re-polarization (recovery).
QRS
complex: due to Ventricular depolarization.(systole).
ECG Paper :
Vertically
= Amplitude and voltage.
Horizontally
= Duration in second.
1
small square = 1 mm(amplitude) = 0.04second.
1
large square = 5 mm (amplitude) = 0.2second.
1m
volt = 10mm(amplitude)
ECG
speed= 25mm/second.
Normal
PR interval = 0.12 – 0.2 sec. (3-5 small
squares)
Normal QRS
duration = 0.12 seconds. (3 small square)
Normal
QT interval = 0.4 seconds.( 2 large
squares)
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