__The 6 Second Rule__:

All but very slow heart rates can be determined by counting the number of cycles that occur within 6 seconds, and then multiplying that number by 10. With very slow bradycardias, counting the number of cycles within 6 seconds may not be enough.

At the standard chart speed of 25mm/sec, five 0.5 cm blocks span 1 second (30 blocks/6 seconds).

At a paper speed of 50mm/sec, 10 blocks span 1 second (60 blocks/6 seconds).

For convenience, most ECG charts mark off every 7.5 cm along the upper margin. These marks correspond to a 3 second interval at a chart speed of 25mm/sec, and a 1.5 second interval at a speed of 50mm/sec.

Ex:

At a paper speed of 25mm/sec, a 6 second strip is selected between the black arrows. The number of heart cycles counted is 7. HR= 7 x 10= 70 bpm.

__Another method for determining the heart rate is "the rule of 300."__

Take the number of “big boxes” between neighboring QRS complexes, and divide this into 300. The result will be approximately equal to the rate

Although fast, this method **only works** for **regular rhythms **and at a **paper speed of 25mm/sec**.

Ex:

At a paper speed of 25mm/sec, what is the HR? 300/6= 50bpm