How to Read an EKG Strip in 5 Steps

The P-Wave, located at the beginning of the ECG cycle, should be present and upright. A P-Wave that is absent or inverted is abnormal.

The P-wave should also not be more than 1 large box tall and 1 large box wide. Normal duration is typically between 0.06 – 0.12 seconds.

The next step is to measure the PR interval. To do this, count the number of small boxes in between the beginning of the P-Wave and the peak of the QRS complex. Then, multiply that number by 0.04 seconds.

Normal interval length should be between 0.12 – 0.20 seconds.

To measure the QRS complex, count the number of small boxes from the beginning to the end of the QRS complex, then divide by 0.04 seconds.

Our normal target range is 0.06 – 0.12 seconds.

There are 3 main categories of rhythms, which are:

• Regular: Constant R to R interval
• Regularly Irregular: Variable R to R interval w/ a pattern
• Irregularly Irregular: Variable R to R interval w/ no pattern

To identify the rhythm, measure the distance between the R waves. Determine if they are consistent throughout the strip.

If the distances are consistent, then the rhythm is regular. If not, the rhythm is irregular.

There are many methods to determine the heart rate using an EKG/ECG. Note that the normal range at rest is between 60 BPM and 100 BPM per minute.

Depending on whether the rhythm is regular or irregular, there are various methods that are widely used to accurately measure heart rate.

The Big Box Method

If the heart rhythm is regular, you can use the Big Box Method. To do this, divide 300 by the number of large boxes in between the R waves.

For example, if there are 5 large boxes in between a set of R’s, the heart rate would be 60 BPM.

The 6 Second Method

If the heart rhythm is irregular and you’re working with a 6-second strip, the 6 second method is an easy and viable option.

First, start by counting the # of R waves from beginning to the end of the 6 second strip. Once you’ve finished counting,  multiply by that number by 10.

For example, if you counted 6 R’s, the heart rate would be 60 BPM.

The Square Counting Method

This method uses the sequence 300-150-100-75-60-50-43-37. Thus, the first thick line is 300, the next is 150, and so on.

First, count from the first QRS complex and stop the sequence at the next QRS complex.  Then, when 2nd QRS complex is in between 2 thick lines. Lastly, take the mean of those 2 lines.

For example, if the 2nd QRS complex lands between 75 and 60, the heart rate would be 67 BPM.