Now let us calculate the heart rate when there is an irregular rhythm. This can be performed by using the “6 second rule”. Measure out 6 seconds anywhere on the ECG strip; most ECG’s already have markers (yellow arrows) every 3 seconds. Count the number of ECG complexes occurring in 6 seconds, and then multiply by 10.

In this example, there are approximately 10 complexes in 6 seconds, and thus, the heart rate is approximately 100 beats per minute.