Which criterion confirms proper atrial activity on a rhythm strip?

• A. R-R interval must be regular
• B. Width of QRS less than 0.12 second
• C. Presence of a P wave with PR ≤ 0.20 seconds for every QRS
• D. QT interval within 0.35-0.43 seconds

Answer: (C)

The key idea is that proper atrial activity is shown when every ventricular beat is preceded by atrial depolarization, seen as a P wave, and conducted to the ventricles within a normal time frame. This is demonstrated by a P wave before each QRS complex with a PR interval of about 0.12 to 0.20 seconds (or at least not longer than 0.20 seconds). When each QRS has a preceding P wave and the PR interval falls within this normal range, it confirms that atrial activity is occurring and being properly conducted to the ventricles.

If a QRS occurs without a preceding P wave or if the PR interval is prolonged beyond 0.20 seconds, atrial conduction or AV conduction may be impaired, which would indicate something other than normal atrial activity. The other measurements relate to ventricular aspects—R-R regularity describes ventricular rhythm, QRS width reflects ventricular depolarization duration, and QT interval concerns ventricular repolarization—not atrial activity.