How is heart rate calculated from an ECG tracing?

The method for calculating heart rate from an ECG tracing using the number of large boxes between R waves is based on the fact that a standard ECG paper is divided into small and large boxes. Each large box typically represents 0.2 seconds, while a small box represents 0.04 seconds.

To determine heart rate using option B, you divide 300 by the number of large boxes between consecutive R waves. Since one minute contains 60 seconds, and the heart rate is expressed in beats per minute (BPM), this approach effectively converts the time interval into a rate. When you count the number of large boxes between two R waves (each representing 0.2 seconds), you can find out how many seconds it takes for one complete heartbeat.

For instance, if there are 3 large boxes between R waves, the time interval would be 0.6 seconds (3 boxes x 0.2 seconds each). To find the heart rate, you can use the formula: 300 divided by the number of large boxes, giving you a heart rate of 100 BPM in this case (300 ÷ 3 = 100).

This method is practical and commonly used in clinical settings due to its simplicity and the ability to provide a quick