PR interval & segment

Make sure you know the difference between the PR segment and the PR interval!

PR segment

The PR segment is the gap between the P wave and the QRS complex. It represents AV node depolarisation. It is also known as the PQ, PTa or PTp segment. A normal PR segment is flat.

PR interval

The PR interval includes everything from the start of the P wave to the end of the PR segment. A normal PR interval is 3-5 mm at standard settings (120 – 200 ms). An abnormal PR interval is caused by abnormal conduction between the atria and ventricles, which can include AV node disease, ectopic junctional rhythms or accessory pathways.