EMS Registry ReadyExample 1 · lead II · 6 seconds
- Rate
- 97/min10 QRS complexes in 6 seconds × 10 = 100/min
- Rhythm
- Regular
- P waves
- Sinus: upright in II, biphasic in V1, one before every QRS
- P to QRS
- 1:1, a P before every QRS
- PR
- 0.10 s
- QRS
- 0.12 s, wide
Sinus rhythm with WPW (pre-excitation) on an ECG strip
A short PR (under 0.12 s), a slurred upstroke at the start of the QRS (the delta wave) and a QRS over 0.11 s.
What to look for
An accessory pathway carries the impulse from the atria to the ventricles without the AV node's delay, so the PR is short. The ventricles start activating early and slowly from where the pathway inserts, and that's the delta wave. Then normal conduction catches up, so the QRS widens by about as much as the PR shortens. The ST and T lean away from the delta wave. A left-sided pathway (type A) is positive in all the chest leads, with R taller than S in V1. A right-sided one (type B) is negative in V1-V2. Watch the negative delta waves: they can mimic Q waves (pseudo-infarction).
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
- P waves
- Sinus: upright in II, biphasic in V1, one before every QRS
- P to QRS
- 1:1, a P before every QRS
- PR
- 0.08 s
- QRS
- 0.13 s, wide
Example 3 · lead II · 6 seconds
- Rate
- 65/min7 QRS complexes in 6 seconds × 10 = 70/min
- Rhythm
- Regular
- P waves
- Sinus: upright in II, biphasic in V1, one before every QRS
- P to QRS
- 1:1, a P before every QRS
- PR
- 0.10 s
- QRS
- 0.14 s, wide
Don't confuse it with
- First-degree AV block
Sinus rhythm with every P conducted, but a constant PR over 0.20 s.
- Sinus rhythm with PJCs
An early narrow QRS with no sinus P before it, and an inverted P just before, inside or just after it.
- Sinus rhythm with right bundle branch block
A QRS of 0.12 s or more with rSR' (an 'M') in V1-V3 and a wide, slurred S in I, aVL, V5 and V6.
- Sinus rhythm with left bundle branch block
A QRS of 0.12 s or more with a deep, broad S (QS or rS) in V1 and a broad R with no Q wave in I, aVL, V5 and V6.
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