Sinus Tachycardia

Sinus Tachycardia is a Sinus Rhythm with a rate greater than 99bpm and is otherwise identical to NSR. This fast rate results in a short R-R Interval on the EKG tracing and more frequent complexes per length.

EKG monitor simulation of Sinus Tachycardia at a rate of 124bpm.
Sinus Tachycardia (sinus tachy) EKG / ECG monitor capture (software gen.)

As a type of Sinus Rhythm, Sinus Tachycardia will have the prototypical P-QRS-T pattern of Normal Sinus Rhythm and Sinus Bradycardia. The tachy in Sinus Tachycardia means fast. A Sinus Rhythm is fast when its HR is greater than 99 (the highest rate of NSR.)

EKG Vocabulary:
Sinus Bradycardia is shortened to "sinus tach" by many healthcare providers.
1:00 Sinus Tachycardia monitor capture.

Once a tracing is identified as a Sinus Rhythm with a Heart Rate (HR) of more than 99bpm it can be called Sinus Tachycardia. Sinus Tachycardia means:

An EKG rhythm starting at the SA Node with a rate above 99 which follows the expected electrical path through the heart.

Defining Characteristic of Sinus Tachycardia in Lead II

Sinus Tachycardia ECG monitor capture.
EKG tracing of a Sinus Tachycardia.

The only differentiating factor of Sinus Tachycardia from other Sinus Rhythms is the rate:

  • Rate: > 99 | R-R Intervals shorter than 0.60sec (15mm) [3 large boxes].

In the below example you can see the maximum R-R Interval (marked in dark green) that a Sinus Tachycardia can have, 15mm (0.60sec) [3 large boxes]. A longer R-R Interval would result in a HR of 99bpm or fewer (making it NSR or Sinus Bradycardia.)

Sinus Tachycardia with its minimum HR of 100bpm.
Sinus Tachycardia with the minimum HR of 100bpm and the R-R Interval marked in green.
Clinical Pearl:
Sinus Tachycardia is in the category of Narrow Complex Tachycardias.

Extremely Fast Rates of Sinus Tachycardia

When the P-QRS-T pattern of all Sinus Rhythm's is present a rhythm is Sinus Tachycardia regardless of how fast it becomes. As the rate of Sinus Tachycardia increases, complexes become closer and closer together. At some point, it becomes impossible to see the details of P and T waves. The specific rate at which this happens varries from case to case.

Once a rhythm reaches a rate where the waves between QRS complexes can't be clearly interpreted it is referred to as Supraventricular Tachycardia.
Supraventricular Tachycardia highlighting the absence of a clear origin.
Monitor capture of a Supraventricular Tachycardia, as complexes are too close together (fast) to identify an origin.

The above EKG cannot be called a Sinus Tachycardia because the P-QRS-T pattern of Sinus Rhythms is not visible. The S-Q Segment has been highlighted in grey, note how P and T waves are not discernible. In a clinical setting it would be called Supraventricular Tachycardia because the complexes are so frequent that there isn't room for P and T waves to be seen between them.

Below are several more examples of Sinus Tachycardia presented as monitor captures as well as on EKG graphs.

Sinus Tachycardia ECG example, split printout / monitor display.
Sinus Tachycardia practice ECG tracing.
Sinus Tachycardia EKG example, split printout / monitor display.
Practice Sinus Tachycardia EKG.
Sinus Tachycardia ECG example, split monitor / paper display.
Practice Sinus Tachycardia ECG.

After becoming familiar with identifying Sinus Tachycardia EKG tracings you can read about other Narrow Complex Tachycardias in Supraventricular Tachycardia or review Normal Sinus Rhythm. Head back to our EKG Rhythm Index to find information on another ECG. Otherwise, practice interpreting novel EKG's with our EKG Generator:

Basic EKG App

Our Basic EKG Generator is free with an email signup and covers Normal Sinus Rhythm along with common arrhythmia.

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