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Rates >100 represent tachycardia. Whether they are sinus is dependent on other factors.

Sinus tachycardia

Sinus rhythm with a rate of  >100 per minute. RR interval less than 3 big boxes (0.6 secs).

Sinus Tachycardia can be seen in:

and many other conditions.


Sinus Bradycardia

Sinus rhythm with a rate of < 60 per minute. RR interval more than 5 big boxes (1 sec)

Sinus Bradycardia can be seen in:


Premature atrial beats (P')


Paroxysmal Atrial Tachycardia.


Paroxysmal Atrial Tachycardia. with block.


Multifocal atrial tachycardia.


Atrial Flutter


Ventricular Tachycardia


Idioventricular rhythm


  Atrial fibrillation 


Ventricular Fibrillation


Premature supraventricular complexes 


Premature ventricular complexes (PVC)