What is the normal PR interval range?

• A. 0.12-0.20 seconds
• B. 0.05-0.08 seconds
• C. 0.25-0.30 seconds
• D. 0.40-0.60 seconds

Answer: (A)

The PR interval shows how long it takes for the impulse to travel from the atria through the AV node and into the ventricles, measured from the start of the P wave to the start of the QRS complex. In a healthy adult, this conduction time falls within 0.12 to 0.20 seconds (120–200 ms), roughly 3–5 small boxes on standard ECG paper. This range reflects normal AV nodal conduction.

If the interval is shorter than 0.12 seconds, it’s not considered normal and can occur with conditions that speed up conduction, such as pre-excitation syndromes. If the interval is longer than 0.20 seconds, it indicates slower AV conduction, as seen with first-degree AV block or other forms of AV block. So the 0.12–0.20 seconds interval is the one that represents normal AV conduction time.