Date Published

February 11, 2020

Updated For

ALS PCS Version ALS PCS 5.2


Calculation of heart rate is important because a deviation from normal may affect the patient™s ability to maintain adequate blood pressure and cardiac output. There are several methods for calculating heart rate:

Six-Second Method: Count the number of QRS complexes within a 6 second strip (30 large boxes) and multiply by 10 to find the number of complexes in a minute.






For the following methods, the rhythm must be regular.

Large Boxes: Count the number of large boxes between one R-R interval and divide into 300.

Small Boxes: Count the number of small boxes between one R-R interval and divide into 1500.

Sequence Method: Select an R wave that falls on a dark vertical line. Number the next 6 consecutive dark vertical lines as follows: 300, 150, 100, 75, 60, 50. Note where the next R wave falls in relation to the 6 dark vertical lines = this is the heart rate.


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