EMS Registry ReadyExample 1 · lead II · 6 seconds
- Rate
- 41/min4 QRS complexes in 6 seconds × 10 = 40/min
- Rhythm
- Regular
- P waves
- Upright in II, uniform
- P to QRS
- 2:1, one P in each group is not conducted
- PR
- 0.16 s
- QRS
- 0.15 s, wide
2:1 AV block on an ECG strip
Two P waves for every QRS: every other P isn't conducted, and the conducted beats all have the same PR. From 2:1 alone you can't call it type I or type II.
What to look for
Two P waves for every QRS, with the P waves marching at a steady rate and the PR on the conducted beats never changing. Mobitz I and II are told apart by what the PR does over two or more conducted beats in a row, and at 2:1 you never get two in a row. So the strip can't tell you the type. Clues help: a narrow QRS leans toward the AV node (type I), a wide QRS toward block below it (type II), and a longer strip often shows a Wenckebach cycle or a Mobitz II drop that settles it. Treat it as the dangerous kind until you know otherwise: atropine may not help a block below the node, so have pacing ready.
Examples
Each strip is 6 seconds of lead II, drawn to scale (25 mm a second, 10 mm a millivolt), so you can count boxes the way you would on paper. Each one is a different example, measured below it.
Example 2 · lead II · 6 seconds
- Rate
- 49/min5 QRS complexes in 6 seconds × 10 = 50/min
- Rhythm
- Regular
- P waves
- Upright in II, uniform
- P to QRS
- 2:1, one P in each group is not conducted
- PR
- 0.23 s
- QRS
- 0.13 s, wide
Example 3 · lead II · 6 seconds
- Rate
- 38/min4 QRS complexes in 6 seconds × 10 = 40/min
- Rhythm
- Regular
- P waves
- Upright in II, uniform
- P to QRS
- 2:1, one P in each group is not conducted
- PR
- 0.15 s
- QRS
- 0.15 s, wide
Don't confuse it with
- Second-degree AV block, type II
A constant PR, then a P wave that suddenly isn't conducted. The QRS is often wide.
- Second-degree AV block, type I (Wenckebach)
The PR lengthens beat by beat until a P wave is not conducted, then resets: grouped beating.
- Sinus bradycardia
Everything normal sinus rhythm has, but under 60/min.
- Sinus rhythm with blocked PACs
An early P wave on the T wave with no QRS after it, then a pause.
Want a new strip every time? The ECG Drill in the app draws a fresh, measured example on every try and steers you toward the rhythms you miss. It's part of the Paramedic level, and you can try 5 strips a day free.
Try the ECG Drill