Heart Rate Calculation : ECG interpretation quick review

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ECG interpretation is an important skill for any healthcare professional.

How to calculate the Heart rate?

Several methods can be employed to ascertain the heart rate.

One straightforward and expedient approach involves

Identifying a QRS complex aligned with a prominent vertical grid line.
followed by counting the number of large squares to the subsequent QRS complex.
Dividing 300 by this count provides the heart rate.

Example:

In the presented ECG, there are 2 large squares between QRS complexes, resulting in a calculated heart rate of 150 beats per minute.

Note: This method only works if the paper speed is set to standard i.e. 25mm/second. At the standard speed of 25mm/s,

each large square = 0.2 second
each small square = 0.04 second

Similarly, this method only works if the heart rhythm is regular. You can find how to assess heart rhythm and calculate heart rate for abnormal rhythm in this article.

Abnormal Heart Rate :

Normal heart rate is considered to be 60 to 100 beats per minute (bpm).

Bradycardia is a condition when the heart rate is less than 60 bpm. Causes of bradycardia can be either normal phenomena e.g. sinus bradycardia in athletes, or serious underlying illnesses like Second-degree and third-degree heart block, myocarditis, amyloidosis, etc.

Tachycardia is a condition when the heart rate is greater than 100 beats per minute. Tachycardia also has a wide variety of physiological, metabolic, and pathologic causes.

You can see the video explanation for the calculation of heart rate from EKG below :

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