The best method for measuring the heart rate in irregular rhythms with varying R-R intervals is to count the number of R waves in a 6-second (sec) ECG strip. Count the blocks/pauses or extra beats such as premature ventricular contractions (PVCs), premature atrial contractions (PACs), and premature junctional contractions (PJCs) and multiply by 10 (see "Method 3: ECG Test Strip Heart Rate Calculation" on page 49). This gives you the average number of beats per minute. When you include the blocks/pauses and extra beats, make sure you put that in your rate, such as 70 bpm (counting pause), 100 bpm (counting PVCs), or 60 bpm (counting PAC). You can also calculate approximate hearts rates for regular rhythms using the 6-second method; however, Method 2: Precise Heart Rate Calculation gives you a more accurate heart rate and is used for measurements throughout this book and in the Tab on ECG Test Strips.

Remember, time is measured in the horizontal direction on the ECG strip. Notice the ECG strip on page 49 (“Method 3: ECG Test Strip Heart Rate Calculation”) has 1-sec marks across the top of the ECG paper. The total number of 1-sec marks in the strip is six. To calculate bpm, count the number of R waves in the 6-sec ECG strip and multiply that by 10 (there are ten 6-sec intervals in 1 minute). Therefore, seven R waves multiplied by 10 equals 70. The overall heart rate should be documented as 70 bpm (counting blocked beat) for the same ECG strip. There is also a heart rate in the underlying rhythm of 75 bpm (see Heart Rate in Underlying Rhythm).