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)