EMS Registry ReadyExample 1 · lead II · 6 seconds
- Rate
- 50/min5 QRS complexes in 6 seconds × 10 = 50/min
- Rhythm
- Regular, except where beats drop
- P waves
- Upright in II, uniform
- P to QRS
- 6:5, one P in each group is not conducted
- PR
- 0.16 s
- QRS
- 0.14 s, wide
Second-degree AV block, type II on an ECG strip
A constant PR, then a P wave that suddenly isn't conducted. The QRS is often wide.
What to look for
The PR stays constant, then a P wave suddenly fails to conduct. No warning, no lengthening. The P-P stays regular, and the R-R around a dropped beat is exactly two P-P intervals. The QRS is usually wide, because the block is below the AV node. With 2:1 conduction, you can't tell the type from the strip.
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
- 67/min6 QRS complexes in 6 seconds × 10 = 60/min
- Rhythm
- Regular, except where beats drop
- P waves
- Upright in II, uniform
- P to QRS
- 5:4, one P in each group is not conducted
- PR
- 0.16 s
- QRS
- 0.16 s, wide
Example 3 · lead II · 6 seconds
- Rate
- 65/min6 QRS complexes in 6 seconds × 10 = 60/min
- Rhythm
- Regular, except where beats drop
- P waves
- Upright in II, uniform
- P to QRS
- 3:2, 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 I (Wenckebach)
The PR lengthens beat by beat until a P wave is not conducted, then resets: grouped beating.
- Third-degree (complete) AV block
P waves and QRS complexes each regular but unrelated: no P is conducted, so the PR is all over the place.
- 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