How to Measure a QRS Complex on an EKG Strip | QRS Complex Measurement Quiz

When you are learning to interpret heart rhythms on an EKG, you must learn how to measure the QRS complex. The QRS complex is the spike on the EKG strips, which is after the p-wave. The QRS complex represents ventricular contraction (depolarization) of the heart’s electrical conduction system.

In the previous article, we discussed how to measure the PR interval and how to count a heart rate on an EKG strip using the 6 second rule, so now we are going to discuss how to measure a QRS complex.

The QRS complex tends to be wide in ventricular tachycardia (v-tach) and very narrow in sinus tachycardia. In this article, I am going to explain how to easily measure the QRS complex. At the end of this article is a quick quiz you can take to test your knowledge on measuring the QRS complex

Video Tutorial on How to Measure the QRS Complex

Steps on How to Measure the QRS Complex

A normal QRS complex measures 0.06 to 0.12 seconds which is 1.5 to 3 small boxes on the EKG strip. When you measure the QRS complex you start by measuring at the END of the PR interval to the END of S-wave.

Here are some simple steps on how to measure the QRS complex:

1. Find the QRS on the EKG strip
2. Determine where the QRS complex is, and to do this you start measuring the END of the PR interval to the END of S-wave.
3. Count the SMALL boxes between there measurements.
4. Remember each box represents 0.04 seconds. So, if you measure 2 boxes the measurement of the QRS complex would be 0.08.

QRS Complex Quiz

Now let’s practice by looking at some QRS complexes and test your knowledge.

 

For figure 1, what is the measurement of the QRS complex? (see answer key below)

 

 

For figure 2, what is the QRS complex measurement? (see answer key below)

 

 

For figure 3, what is the QRS complex measurement? (see answer key below)

ANSWER KEY:

Figure 1: 0.16 (Rational: there are 3 whole boxes and 2 half box, so 0.02+0.04+0.04+0.04+0.02=0.16 seconds)

Figure 2:0.06 (Rational: there is 1 whole boxes and 1 half box, so 0.02+0.04=0.06 seconds)

Figure 3: 0.14 (Rational: there are 3 whole boxes and 1 half box, so 0.04+0.04+0.04+0.02= 0.14 seconds)