EkgHeartRateRhythm

The EKG paper is made of a grid of big boxes and small boxes. The EKG paper is made of a grid of big boxes and small boxes. Each big box is 10 mm in length has five small boxes and is 0.20 sec. Each small box is 1 mm and represents 0.04 sec. The EKG paper moves at a standard speed of 25 mm/sec. At standard speed, the heart rate can be determined by either of the following methods.

Method I

Examine the distance between QRS complexes and determine if the peaks (RR intervals) are regularly spaced.

The EKG below shows regular RR intervals. If the RR distances are regular, count the number of "small boxes" from the beginning of one QRS complex to the beginning of the next QRS complex. Then divide 1500 by the number of "small boxes" to obtain the heart rate in beats per minute.

Heart Rate =	1500
	No. small boxes

The EKG on the bottom right shows irregularly spaced RR intervals. If the distances are irregular, count the number of QRS complexes within 30 large boxes (which each represent 0.2 seconds) and multiply this number by 10 to obtain the heart rate in beats/minute.

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Method II

If the peaks are regular, the heart rate can be estimated using the EKG grid. To do this locate a QRS complex on a bold line. If the next QRS complex is separated by:

i. One large box, the heart rate is 300 BPM (300/1)
ii. Two large boxes, the heart rate is 150 BPM (300/2)
iii. Three large boxes, the heart rate is 100 BPM (300/3)
iv. Four large boxes, the heart rate is 75 BPM (300/4)
...and so on.

The EKG grid used to rapidly estimate the heart rate

The difference between Atrial and Venticular Rates

The heart rate calculated using the RR intervals is the venticular rate. In sinus rythm, the venticular rate corresponds to the atrial rate. Tthe atrial rate can be determined from the PP interval using either of the two methods above.

Last Updated: 01/03/00.
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