Observe the P waves size and shape and where it appears in the waveform.
If the P wave is consistently followed by a QRS complex, the cardiac
cycle is being initiated in the SA node, as it should be, and is
being transmitted to the ventricles.

2. Evaluate the Atrial Rhythm

The P waves should occur with a regular frequency, with only small
variations associated with respiration. The interval between P waves,
the P-P interval, is most easily measured by the using calipers.
Compare the P-P intervals in several cycles. Be certain the calipers
are set at the same point on the rhythm strip, at the beginning
of the wave or on its peak. Instead of lifting the calipers, rotate
the leg to the next P wave to be certain your measurements are accurate.

3. Evaluate the Atrial Rate

A rapid way to determine the rate is to count the number of P waves
in two 3-second segments and to multiply this number by 10. You
may also use the other two methods if the rhythms are regular.

4. Calculate Duration of the P-R Interval

Count the number of small squares between the beginning of the P
wave and beginning of the QRS complex. Multiply the number of squares
by .04 seconds. The normal interval is between 0.12 and 0.20 seconds.
If it is wider, then there is a delay in the conduction of the impulse
to the ventricles.

5. Evaluate Ventricular Rhythm

Use calipers to measure the R-R intervals. Remember to place the
calipers on the same point of the QRS complex. If the R-R intervals
are consistantly the same, the ventricular rhythm is regular.

6. Evaluate Ventricular Rate

The ventricular rate normally is the same as the atrial rate. Use
the same method described to calculate the atrial rate. Also check
the QRS complex and decide if it looks as it should for the lead
you are monitoring.

7. Calculate the Duration of the QRS Complex

Count the number of squares between the beginning of the Q wave
and the end of the S wave and multiply by 0.04 second. A normal
QRS complex duration is 0.12 second.

8. Calculate the Duration of the Q-T Interval

Count the number of squares from the beginning the the Q wave to
the end of the T wave, then multiply this number by 0.04 second.