The PR interval on an electrocardiogram measures the time from the start of atrial depolarization to the start of ventricular depolarization. What range is considered normal?

The PR interval on an electrocardiogram measures the time from the start of atrial depolarization to the start of ventricular depolarization. What range is considered normal?

• A. 0.12-0.20
• B. 0.04-0.12
• C. 0.08-0.16
• D. 0.20-0.25

Answer: (A)

The PR interval measures the time from the start of atrial depolarization to the start of ventricular depolarization. It reflects how long it takes for electrical conduction to travel from the atria through the AV node and into the ventricles. The normal range is 0.12 to 0.20 seconds (120–200 milliseconds). This interval accounts for the typical AV nodal delay that allows the ventricles to fill properly before they contract. Values outside this range have clinical meaning: longer than 0.20 seconds suggests slowed AV conduction (first-degree AV block), while shorter intervals can indicate pre-excitation or accessory pathways, though those scenarios have distinct features beyond just the interval length. So, the range 0.12–0.20 seconds corresponds to normal PR interval.

The PR interval measures the time from the start of atrial depolarization to the start of ventricular depolarization. It reflects how long it takes for electrical conduction to travel from the atria through the AV node and into the ventricles.

The normal range is 0.12 to 0.20 seconds (120–200 milliseconds). This interval accounts for the typical AV nodal delay that allows the ventricles to fill properly before they contract. Values outside this range have clinical meaning: longer than 0.20 seconds suggests slowed AV conduction (first-degree AV block), while shorter intervals can indicate pre-excitation or accessory pathways, though those scenarios have distinct features beyond just the interval length.

So, the range 0.12–0.20 seconds corresponds to normal PR interval.