In Normal Sinus Rhythm, the P wave duration is within which range?

• A. 0.08-0.12 seconds
• B. 0.28-0.36 seconds
• C. 0.12-0.20 seconds
• D. 0.20-0.28 seconds

Answer: (C)

P wave duration reflects how long atrial depolarization takes. In a normal sinus rhythm, this interval is short because atrial activation is quick and efficient. The typical upper limit you’ll see in most references is about 0.12 seconds (roughly three small boxes on the ECG). If the P wave lasts significantly longer than that, it can indicate slowed atrial conduction or atrial enlargement.

In the context of the answer you’ve got, remember that the time from the start of the P wave to the start of the QRS complex (the PR interval) is normally 0.12 to 0.20 seconds. This is a common source of confusion because the PR interval and the P wave duration are different measurements. The key point for P wave duration is that it should be brief—typically up to 0.12 seconds—and longer durations point to atrial conduction issues.