Individuals with atrial septal defects may have a prolonged PR interval (a first degree heart block).

First degree AV block - PR interval greater than 0.20sec.

Prolongation of the PR interval may also lead to an abnormal heart rhythm known as heart block.

Variations in the PR interval can be associated with certain medical conditions:

A long PR interval (of over 200 ms) may indicate a first degree heart block.

A variable PR interval may indicate other types of heart block.

The normal PR interval is from 120 ms to 200 ms in length.

This would present with a longer PR interval.

A prolongation of the PR interval (a conduction disturbance in the heart) is also frequently seen.

PR interval is between .12 second and .20 second.