EMS Registry ReadyExample 1 · lead II · 6 seconds
- Rate
- 78/min8 QRS complexes in 6 seconds × 10 = 80/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
- 0.14 s
- QRS
- 0.08 s, narrow
Prolonged QT interval on an ECG strip
Sinus rhythm with a QT too long for the rate: the T wave ends late, a QTc of 500 ms or more here, where the risk of torsades climbs.
What to look for
Measure from the start of the QRS to the end of the T wave in II, V5 or V6, using the longest one you can find, and end the T where its steepest downslope meets the baseline. Then correct for rate. A QTc over 440 ms in men or 460 ms in women is long, and past 500 ms the risk of torsades climbs. Near a rate of 60-80, a quick check works: the QT should be less than half the R-R. The usual causes are drugs, low potassium, magnesium or calcium, hypothermia, raised intracranial pressure, and the congenital syndromes.
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
- 60/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
- 0.13 s
- QRS
- 0.10 s, narrow
Example 3 · lead II · 6 seconds
- Rate
- 83/min8 QRS complexes in 6 seconds × 10 = 80/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
- 0.17 s
- QRS
- 0.09 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.
- First-degree AV block
Sinus rhythm with every P conducted, but a constant PR over 0.20 s.
- Normal 12-lead ECG
Sinus rhythm, a normal axis, normal intervals, R waves growing from V1 to V5, and no ST elevation or depression.
- Hyperkalemia (peaked T waves)
T waves that are tall, narrow at the base and peaked, best seen in the chest leads. As potassium rises, the P wave flattens, the PR lengthens and the QRS widens.
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