EMS Registry ReadyExample 1 · lead II · 6 seconds
- Rate
- 72/min8 QRS complexes in 6 seconds × 10 = 80/min
- Rhythm
- Regular
- P waves
- Upright in II, uniform
- P to QRS
- 1:1, a P before every QRS
- PR
- 0.25 s
- QRS
- 0.10 s, narrow
First-degree AV block on an ECG strip
Sinus rhythm with every P conducted, but a constant PR over 0.20 s.
What to look for
Sinus rhythm with every P conducted, but a constant PR over 0.20 s (5 small boxes). Every P gets through; it just takes longer. A PR over 0.30 s is marked first-degree block.
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
- 77/min7 QRS complexes in 6 seconds × 10 = 70/min
- Rhythm
- Regular
- P waves
- Upright in II, uniform
- P to QRS
- 1:1, a P before every QRS
- PR
- 0.30 s
- QRS
- 0.07 s, narrow
Example 3 · lead II · 6 seconds
- Rate
- 88/min9 QRS complexes in 6 seconds × 10 = 90/min
- Rhythm
- Regular
- P waves
- Upright in II, uniform
- P to QRS
- 1:1, a P before every QRS
- PR
- 0.29 s
- QRS
- 0.08 s, narrow
Don't confuse it with
- Normal sinus rhythm
Regular at 60-100/min, an upright P before every QRS, a PR of 0.12-0.20 s and a narrow QRS.
- Second-degree AV block, type I (Wenckebach)
The PR lengthens beat by beat until a P wave is not conducted, then resets: grouped beating.
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