Which pattern defines second-degree AV block type I (Wenckebach) on telemetry?

Which pattern defines second-degree AV block type I (Wenckebach) on telemetry?

• A. Intermittent dropped QRS without PR prolongation
• B. Progressive PR prolongation followed by a dropped QRS in a repeating pattern
• C. Atria and ventricles beating independently
• D. Wide QRS with constant PR interval

Answer: (B)

The pattern tested is Wenckebach behavior, where the PR interval lengthens step by step and then a beat is dropped, with the cycle resetting afterward. On telemetry you’ll see P waves with progressively longer PR intervals, and eventually a P wave that is not followed by a QRS complex. The rhythm then repeats, indicating that conduction through the AV node is intermittently failing after increasingly delayed transmissions. This reflects a block at the AV node level and is the hallmark of second-degree AV block type I. Other patterns don’t fit this scenario. A dropped QRS without PR prolongation isn’t Wenckebach, and would point toward Mobitz type II. Atria and ventricles beating independently describe complete heart block, with no relation between P waves and QRSs. A wide QRS with a constant PR interval suggests a ventricular origin or a non-nodal conduction issue, not Wenckebach.

The pattern tested is Wenckebach behavior, where the PR interval lengthens step by step and then a beat is dropped, with the cycle resetting afterward. On telemetry you’ll see P waves with progressively longer PR intervals, and eventually a P wave that is not followed by a QRS complex. The rhythm then repeats, indicating that conduction through the AV node is intermittently failing after increasingly delayed transmissions. This reflects a block at the AV node level and is the hallmark of second-degree AV block type I.

Other patterns don’t fit this scenario. A dropped QRS without PR prolongation isn’t Wenckebach, and would point toward Mobitz type II. Atria and ventricles beating independently describe complete heart block, with no relation between P waves and QRSs. A wide QRS with a constant PR interval suggests a ventricular origin or a non-nodal conduction issue, not Wenckebach.