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Free ECG rhythm strip practice
10 rhythm strips to read, drawn to scale: 25 mm a second, 10 mm a millivolt. Work each one the same
way every time: rate, rhythm, P waves, PR, QRS. Then open the answer and check yourself against what the strip measures.
Strip 1 · lead II · 6 seconds
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Junctional escape rhythm
A regular narrow-complex rhythm at 40-60/min with no upright P waves: any P is inverted, just before, inside or just after the QRS.
Rate 45/min4 QRS complexes in 6 seconds × 10 = 40/min
Rhythm Regular
P waves Inverted in II, just before each QRS
P to QRS Each inverted P comes just before its QRS, too close to have conducted it (PR under 0.12 s)
PR None to measure
QRS 0.08 s, narrow More on this rhythm: Junctional escape rhythm
Strip 2 · lead II · 6 seconds
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Atrial fibrillation
Irregularly irregular, with no P waves: only a fibrillating baseline.
Rate 171/min17 QRS complexes in 6 seconds × 10 = 170/min
Rhythm Irregularly irregular
P waves None: fibrillatory baseline
P to QRS No P waves
PR None to measure
QRS 0.10 s, narrow More on this rhythm: Atrial fibrillation
Strip 3 · lead II · 6 seconds
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First-degree AV block
Sinus rhythm with every P conducted, but a constant PR over 0.20 s.
Rate 99/min10 QRS complexes in 6 seconds × 10 = 100/min
Rhythm Regular
P waves Upright in II, uniform
P to QRS 1:1, a P before every QRS
PR 0.26 s
QRS 0.07 s, narrow More on this rhythm: First-degree AV block
Strip 4 · lead II · 6 seconds
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Third-degree (complete) AV block
P waves and QRS complexes each regular but unrelated: no P is conducted, so the PR is all over the place.
Rate 27/min2 QRS complexes in 6 seconds × 10 = 20/min
Rhythm Regular
P waves Upright in II, uniform
P to QRS None: P waves and QRS complexes are independent (AV dissociation)
PR None to measure
QRS 0.16 s, wide More on this rhythm: Third-degree (complete) AV block
Strip 5 · lead II · 6 seconds
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Second-degree AV block, type I (Wenckebach)
The PR lengthens beat by beat until a P wave is not conducted, then resets: grouped beating.
Rate 67/min7 QRS complexes in 6 seconds × 10 = 70/min
Rhythm Regularly irregular: a pattern that repeats
P waves Upright in II, uniform
P to QRS 4:3, grouped; one P in each group is not conducted
PR Lengthens 0.22 s, then 0.31 s, then 0.36 s, then a P is not conducted
QRS 0.10 s, narrow More on this rhythm: Second-degree AV block, type I (Wenckebach)
Strip 6 · lead II · 6 seconds
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Sinus tachycardia
Sinus rhythm over 100/min: regular, with an upright P before every QRS.
Rate 111/min12 QRS complexes in 6 seconds × 10 = 120/min
Rhythm Regular
P waves Upright in II, uniform
P to QRS 1:1, a P before every QRS
PR 0.20 s
QRS 0.08 s, narrow More on this rhythm: Sinus tachycardia
Strip 7 · lead II · 6 seconds
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Polymorphic ventricular tachycardia
A wide-complex tachycardia whose complexes change shape from beat to beat.
Rate 244/min during the run25 QRS complexes in 6 seconds × 10 = 250/min
Rhythm Irregular
P waves Not visible
P to QRS No visible P waves
PR None to measure
QRS None More on this rhythm: Polymorphic ventricular tachycardia
Strip 8 · lead II · 6 seconds
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Torsades de pointes
Polymorphic VT that twists around the baseline in spindles, following a long QT.
Rate 201/min during the run15 QRS complexes in 6 seconds × 10 = 150/min
Rhythm Irregular
P waves Upright in II before the run; not seen during it
P to QRS 1:1 before the run; none during it
PR 0.19 s
QRS 0.10 s, narrowThe beats before the run More on this rhythm: Torsades de pointes
Strip 9 · lead II · 6 seconds
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Monomorphic ventricular tachycardia
Regular, wide and over 100/min, with every complex the same shape.
Rate 107/min11 QRS complexes in 6 seconds × 10 = 110/min
Rhythm Regular
P waves Not visible
P to QRS No visible P waves
PR None to measure
QRS 0.18 s, wide More on this rhythm: Monomorphic ventricular tachycardia
Strip 10 · lead II · 6 seconds
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Supraventricular tachycardia (AVNRT)
Regular, narrow and 150-250/min, with no visible P waves.
Rate 239/min24 QRS complexes in 6 seconds × 10 = 240/min
Rhythm Regular
P waves Not visible
P to QRS No visible P waves (retrograde P buried in the QRS)
PR None to measure
QRS 0.09 s, narrow More on this rhythm: Supraventricular tachycardia (AVNRT)
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 Every rhythm, one page each
What to look for, examples measured box by box, and the rhythms each one gets confused with.
Sinus
Atrial
Junctional
AV blocks
Ventricular
Paced
BBB, WPW, Brugada
EMS Registry Ready