Sinus tachycardia

Sinus tachycardia is defined as a sinus rhythm with a rate of greater than 100 beats per minute and less than approximately 160 to 180 beats per minute. In this tracing, the rate is about 130 beats per minute.

The normal P wave in sinus rhythm is slightly notched since activation of the right atrium precedes that of the left atrium. The P wave is upright in a positive direction in leads I and II. A P wave with a uniform morphology precedes each QRS complex. The rate is between 60 and 100 beats per minute and the cycle length is uniform between sequential P waves and QRS complexes. In addition, the P wave morphology and PR intervals are identical from beat to beat.