Monitor SimulatorECG rhythm strip practice
Fifteen strips, each six seconds long, at 25 mm/s. Pick an answer and the reading opens below it. The strips were drawn by the same engine as the live monitor, at different rates from the ones in the rhythm library, so you cannot just match pictures.
Read every strip the same way
- Rate. Count the QRS complexes in the six seconds and multiply by ten.
- Rhythm. Are the R-R gaps equal, irregular in a pattern, or irregular with no pattern at all?
- P waves. Is there one in front of every QRS? Are there extra ones?
- PR. Normal is 3 to 5 small squares. Is it long, and does it change?
- QRS. Narrow is under 3 small squares. Wide means it started low or travelled slowly.
Strip 1
Show answer
Sinus rhythm
- Rate
- 9 QRS in 6 seconds, about 90.
- Rhythm
- Regular.
- P waves
- Upright, one before every QRS.
- PR
- Normal, just under one large square.
- QRS
- Narrow.
Nothing hidden here. Use it as the reference for the strips that follow.
Strip 2
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Atrial fibrillation
- Rate
- 10 QRS in 6 seconds, about 100.
- Rhythm
- Irregularly irregular. No two R-R gaps match.
- P waves
- None. The baseline wanders between complexes.
- PR
- Not measurable.
- QRS
- Narrow.
Sinus arrhythmia also varies, but it keeps a P wave in front of every QRS and the changes follow breathing. Wenckebach is irregular in a pattern that repeats.
Strip 3
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Third-degree (complete) AV block
- Rate
- 3 QRS in 6 seconds, roughly 30 to 40.
- Rhythm
- QRS regular, P waves regular, but the two have nothing to do with each other.
- P waves
- Present, more of them than QRS complexes, some falling on T waves.
- PR
- Varies with every beat.
- QRS
- Wide. A ventricular escape rhythm.
In 2:1 block the PR of the conducted beats stays the same. Here no PR repeats, which is how you know the atria and ventricles have separated.
Strip 4
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SVT
- Rate
- 17 to 18 QRS in 6 seconds, about 175.
- Rhythm
- Perfectly regular.
- P waves
- Not visible.
- PR
- Not measurable.
- QRS
- Narrow.
Sinus tachycardia rarely runs this fast at rest and shows P waves. Flutter at 150 is the trap to rule out; at 175 and without sawtooth waves this is SVT.
Strip 5
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Mobitz type I (Wenckebach)
- Rate
- 6 QRS in 6 seconds, about 60.
- Rhythm
- Grouped beats separated by pauses.
- P waves
- Regular, one more P than QRS in each group.
- PR
- Gets longer beat by beat until a P wave is not followed by a QRS.
- QRS
- Narrow.
Mobitz II drops a beat without warning, with the PR unchanged before it. Look at the PR right before the pause and right after it: here they differ a lot.
Strip 6
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Ventricular tachycardia
- Rate
- 15 QRS in 6 seconds, about 150.
- Rhythm
- Regular.
- P waves
- None visible.
- PR
- Not measurable.
- QRS
- Very wide and uniform.
A broad regular tachycardia is VT until proven otherwise. Check the patient: with a pulse it is VT, without one it is pulseless VT and shockable.
Strip 7
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First-degree AV block
- Rate
- 7 QRS in 6 seconds, about 70.
- Rhythm
- Regular.
- P waves
- One before every QRS.
- PR
- Long, well over one large square (about 280 ms), and the same every beat.
- QRS
- Narrow.
Every P conducts. If the PR were growing and a beat dropped, it would be Wenckebach.
Strip 8
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Atrial flutter with 2:1 conduction
- Rate
- 15 QRS in 6 seconds, exactly 150.
- Rhythm
- Regular.
- P waves
- Sawtooth flutter waves, two for every QRS.
- PR
- Not measurable.
- QRS
- Narrow.
A regular narrow tachycardia at 150 should always make you hunt for a second flutter wave hidden in the T wave or the QRS.
Strip 9
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Sinus bradycardia
- Rate
- 5 QRS in 6 seconds, about 45 to 50.
- Rhythm
- Regular.
- P waves
- Upright, one before every QRS.
- PR
- Normal.
- QRS
- Narrow.
Compare with strip 12, which has nearly the same rate but no P wave in front of the QRS.
Strip 10
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Hyperkalaemia
- Rate
- 6 QRS in 6 seconds, about 60.
- Rhythm
- Regular.
- P waves
- Small and flat, almost gone.
- PR
- Long where you can see it.
- QRS
- Broadening.
The T waves are tall, narrow and pointed like a tent, with a symmetrical shape. ST elevation instead lifts the segment before a broad T.
Strip 11
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Pacing spikes without capture
- Rate
- No ventricular rate at all. The pacemaker fires about 70 times a minute.
- Rhythm
- Spikes regular.
- P waves
- Small P waves at their own rate.
- PR
- Not applicable.
- QRS
- None. Nothing follows the spikes.
This patient has no ventricular output. Treat it as an arrest while you turn the output up or check the pads.
Strip 12
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Junctional escape rhythm
- Rate
- 5 QRS in 6 seconds, about 50.
- Rhythm
- Regular.
- P waves
- None in front of the QRS. A small inverted P sits just after it.
- PR
- Not applicable.
- QRS
- Narrow.
The retrograde P after the QRS is the clue. A narrow QRS at 40 to 60 with no P in front comes from the AV junction.
Strip 13
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Ventricular fibrillation
- Rate
- Cannot be counted.
- Rhythm
- Chaotic.
- P waves
- None.
- PR
- Not applicable.
- QRS
- No recognisable complexes.
Artefact can look like this, so glance at the patient. If there is no pulse, it is VF and needs a shock now.
Strip 14
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Second-degree AV block, 2:1
- Rate
- 4 QRS in 6 seconds, about 40.
- Rhythm
- Regular.
- P waves
- Two for every QRS. The second is easy to miss next to the T wave.
- PR
- Constant in the conducted beats.
- QRS
- Narrow.
With a fixed 2:1 ratio you cannot tell Mobitz I from II on one strip, because there are no two conducted beats in a row to compare.
Strip 15
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ST elevation
- Rate
- 8 QRS in 6 seconds, about 80.
- Rhythm
- Regular.
- P waves
- One before every QRS.
- PR
- Normal.
- QRS
- Narrow, then the ST segment stays above the baseline.
A monitor lead can raise the suspicion. Get a 12-lead ECG to confirm and localise.
Questions
How do you work out the heart rate from a 6-second strip?
Count the QRS complexes in the six seconds and multiply by ten. It is quick and works for irregular rhythms too, where the 300 and 1500 methods give a different answer for every beat.
What is the best way to practise reading rhythm strips?
Use the same five steps on every strip, even the easy ones, and say each answer out loud before you look. Ten minutes a day does more than an hour once a week.
Can I use these strips in a test or a class?
Yes. Use them in quizzes, slides and handouts. The print button gives you the strips with the answers hidden. A link back to this page is appreciated.
Can I show these rhythms on a live monitor?
Yes. The monitor simulator shows all of these and seven more, live on a tablet while you change the rhythm from your phone. It is a good next step once the strips feel easy: the same rhythm looks different when it is moving and the alarms are going.