Sinus tachycardia is caused by a physiologic, pharmacologic or endocrine stimulus. It can be identified by a number of characteristic findings on the electrocardiogram (ECG).



(1) atrial rate

(2) P waves

(3) ventricular rate and rhythm


Atrial rate: 100-200 beats per minute (rarely up to 220)


P waves have a normal morphology and precede every QRS complex. At high atrial rates it may be masked by the preceding T wave.


Ventricular rate: 100-200 beats per minute (each atrial wave is followed by a ventricular contraction) unless an atrioventricular conduction defect is present


Ventricular rhythm is regular.


Indications that apparent sinus tachycardia is due to another cause (Wagner):

(1) prolonged PR interval

(2) abnormal frontal plane P wave axis

(3) P wave inversion


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