When evaluating the rate of the complexes, first keep in mind that the P-wave rate may be different from the QRS rate. For the purposes of this discussion, we consider QRS rates only. The same principles can be applied to obtain the P-wave rate, if needed.
The rate can be obtained in various ways. If you have a computerized interpretation at the top of the ECG, you can usually use the rate that is given. Keep in mind, however, that this rate may be wrong. If it appears to be the wrong rate, calculate it yourself. One way of calculating the rate is to use a ruler, such as the one mentioned earlier in this chapter. There are also ways of calculating rate using the rhythm strip itself and your basic knowledge of the time intervals involved. Using your calipers with these techniques will be very helpful. Let’s look at some of those ways now.