Write briefly about different waves and intervals in an ECG.

Electro cardiogram is a non invasive method of recording heart's electrical activity.
* This electrical activity is recorded on a paper in a graphical form.
* An electrocardiogram consists of waves, complexes, intervals and segments.
Waves :
1) P wave : It represents the atrial systole.
2) QRS complex : It represents ventricular systole.
3) T wave : It represents ventricular repolarisation.
Intervals :
1) P-R interval : Time between P and Q wave.
2) Q-T interval : Time between Q and end of T wave.
3) R-R interval : It indicates one cardiac cycle.