EMS Registry ReadyExample 1 · lead II · 6 seconds
- Rate
- 197/min19 QRS complexes in 6 seconds × 10 = 190/min
- Rhythm
- Irregularly irregular
- P waves
- None: fibrillatory baseline
- P to QRS
- No P waves
- PR
- None to measure
- QRS
- 0.18 s, wide
Pre-excited atrial fibrillation (AF with WPW) on an ECG strip
Very fast (often over 200/min), irregularly irregular, with wide QRS complexes that change width and shape from beat to beat: AF racing down an accessory pathway.
What to look for
In ordinary AF the AV node acts as a brake, so the ventricles can't follow every fibrillating wave. An accessory pathway has no brake. The ventricles get driven very fast, over 200/min in places, irregularly irregular, and each QRS is a different mix of pathway and node: wide and bizarre, changing width and shape beat to beat. The danger is in the treatment. AV nodal blockers (adenosine, diltiazem, verapamil, beta blockers, and amiodarone per many references) can push more conduction down the pathway and into VF. Unstable means synchronized cardioversion; stable means your protocol's alternative, often procainamide.
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
- 205/min20 QRS complexes in 6 seconds × 10 = 200/min
- Rhythm
- Irregularly irregular
- P waves
- None: fibrillatory baseline
- P to QRS
- No P waves
- PR
- None to measure
- QRS
- 0.14 s, wide
Example 3 · lead II · 6 seconds
- Rate
- 225/min22 QRS complexes in 6 seconds × 10 = 220/min
- Rhythm
- Irregularly irregular
- P waves
- None: fibrillatory baseline
- P to QRS
- No P waves
- PR
- None to measure
- QRS
- 0.15 s, wide
Don't confuse it with
- Polymorphic ventricular tachycardia
A wide-complex tachycardia whose complexes change shape from beat to beat.
- Atrial fibrillation
Irregularly irregular, with no P waves: only a fibrillating baseline.
- Monomorphic ventricular tachycardia
Regular, wide and over 100/min, with every complex the same shape.
- SVT with aberrant conduction
Regular, wide and 150-250/min, in the same bundle branch block shape as the sinus beats before it.
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