Can we calculate the rate?

Now that we have learned how to read EKGs, let's learn how to calculate the heart rate.  It is very simple.  Each large box has 5 small boxes with each small box equal to .04.  5x.04= 0.2.  Each large box = 0.2 seconds each.  1 second = 5 cycles or beats per minute (bpm) ( 1 divided by 0.2 = 5 ).  Then 1 minute equals 300 cycles of heart beats or beats per minute (5 x 60 seconds = 300).  If each R wave to R wave measures one large box then the heart rate is 300 bpm.  2 large boxes = 150 bpm (0.2 + 0.2 = 0.4), 3 large boxes = 100 bpm, 4 large boxes = 75 bpm, 5 large boxes = 60 bpm, and 6 large boxes = 50 bpm.  The easiest way to count the rate of this rhythm is to look at the R wave and the heavy long line (start/red arrow).  Count each large box between each R wave.  In this strip there are almost 4 boxes between each R wave. 4 large boxes = 75 and it is just shy of 4 large boxes therefore this heart rate is approximately 75-80 bpm.  Understanding the rate of a rhythm can tell alot about what kind of rhythm it is.  We will discuss the different rhythm rates another time.  Another way to make it easy is to count the R to R wave large boxes and divide the number of boxes into 300.  For example, this R to R wave is 4 large boxes therefore, 300 divided by 4 = 75. 
Here is another way to do a rapid heart rate count.

Using the formula above, can you see how we arrived at the rhythm rates you see?  Look at the following rhythms below and try to figure out the rhythm rates.  If you have any questions, feel free to ask Marna.

Can you identify the rate and rhythms?