The second step in interpreting an ECG rhythm is to calculate the heart rate or number of heart beats in a minute. Both the atrial and ventricular rates need to be identified.
There are a number of ways to determine rates. The first method for identifying the heart rate is the easiest, simplest, and fastest but the least accurate.
It can be used to estimate the heart rate regardless of whether the rhythm is regular or irregular. ECG paper is marked in three-second intervals or sometimes every second. Every five large boxes equal one second.
Simply count the number of QRS complexes in any six-second interval and multiply this number by ten. The atrial rate can be calculated the same way using P waves. This is the only method to be used when the rhythm is irregularly irregular as it will most closely estimate the heart rate.