EMS Registry ReadyExample 1 · lead II · 6 seconds
- Rate
- 61/min6 QRS complexes in 6 seconds × 10 = 60/min
- Rhythm
- Irregularly irregular
- P waves
- None: fibrillatory baseline
- P to QRS
- No P waves
- PR
- None to measure
- QRS
- 0.08 s, narrow
Atrial fibrillation on an ECG strip
Irregularly irregular, with no P waves: only a fibrillating baseline.
What to look for
No P waves, just a chaotic fibrillatory baseline. The R-R intervals are irregularly irregular, with no repeating pattern to find. Atrial activity runs 350-600/min, and you can't count it. Fine waves are under 0.5 mm (half a small box); coarse waves are bigger.
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
- 78/min8 QRS complexes in 6 seconds × 10 = 80/min
- Rhythm
- Irregularly irregular
- P waves
- None: fibrillatory baseline
- P to QRS
- No P waves
- PR
- None to measure
- QRS
- 0.08 s, narrow
Example 3 · lead II · 6 seconds
- Rate
- 75/min7 QRS complexes in 6 seconds × 10 = 70/min
- Rhythm
- Irregularly irregular
- P waves
- None: fibrillatory baseline
- P to QRS
- No P waves
- PR
- None to measure
- QRS
- 0.10 s, narrow
Don't confuse it with
- Atrial flutter
Sawtooth waves at about 300/min, with a QRS after every 2nd, 3rd or 4th wave.
- Multifocal atrial tachycardia
Irregular, over 100/min, with three or more different P-wave shapes and a PR that varies.
- Sinus arrhythmia
Sinus P waves and a constant PR, but the rate speeds up and slows down with breathing: the P-P varies by more than 0.12 s.
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