Which method is NOT used to calculate heart rate from an ECG tracing?

Calculating heart rate from an ECG tracing can be done using several established methods, and it's essential to know the correct formulas to apply.

When looking at option C, multiplying the number of small boxes by 2 is not a recognized method for heart rate calculation from an ECG. This approach misrepresents the relationship between the number of boxes and the heart rate, as it does not incorporate the knowledge of how these boxes correspond to time intervals.

The other methods mentioned are valid for calculating heart rate. Utilizing the formula of 300 divided by the number of large boxes between R waves provides a quick way to estimate heart rate based on the standard 300 large boxes representing one minute on a standard ECG paper strip. The method of dividing 1500 by the number of small boxes between R waves is also accurate because it accounts for the fact that there are 1500 small boxes in one minute. Moreover, counting the number of beats in a 6-second strip and multiplying by 10 allows for a straightforward calculation of the beats per minute (BPM) based on a 6-second interval.

Thus, option C does not represent a method used in clinical practice to calculate heart rate from an ECG tracing.