elongated. This is usually indicative of some
type of AV block. Careful attention should be paid to the P-wave
and P-R interval when assessing ECG rhythm.
The P-R interval is measured from the beginning of the
P-wave to the beginning of the Q-wave's downward deflection. This
represents the time necessary for the SA node impulse to spread
over the atria and through the AV node. This normally takes 0.12
to 0.2 seconds (4-5 small boxes). When conduction through either
the atrial muscle, internodal pathways or the AV node is slowed,
the P-R interval is
elongated. This is usually indicative of some
type of AV block. Careful attention should be paid to the P-wave
and P-R interval when assessing ECG rhythm.