Rhythm library

EKG rhythms, labeled and compared

Forty-two rhythms that nursing school, telemetry competency exams and ACLS expect you to recognize on a 6-second strip. They are grouped by where the rhythm comes from, because that is what decides how the strip looks. Each has its own page with measured examples and a short drill.

Jump to: Sinus rhythms · AV blocks · Supraventricular rhythms · Junctional rhythms · Ventricular rhythms · Paced rhythms · Arrest rhythms · Comparison chart

Sinus rhythms

The SA node is in charge and every beat has a normal P wave. They differ in rate and in how evenly the beats are spaced. Learn the normal numbers first.

Normal sinus rhythm

Regular, with one P wave in front of every QRS. The yardstick for everything else.

Sinus bradycardia

Normal sinus rhythm in every way except the rate, which is below 60.

Sinus tachycardia

Normal sinus rhythm in every way except the rate, which is above 100. The P waves are still there.

Sinus arrhythmia

Sinus rhythm that speeds up and slows down gradually. Every beat has a P wave and none is early.

Sinus arrest (sinus pause)

Sinus rhythm interrupted by a pause with no P wave and no QRS.

Sinus rhythm with bundle branch block

A P wave before every QRS and a normal PR interval, but the QRS is wide and notched.

AV blocks

The P waves are normal. What changes is whether, and how late, each one reaches the ventricles. Decided by the PR interval.

All four heart blocks compared

First-degree AV block

Every P wave conducts, but the PR interval is long and stays the same.

Second-degree AV block, type I (Wenckebach)

The PR interval gets longer, longer, longer, then a QRS is dropped.

Second-degree AV block, type II (Mobitz II)

The PR interval never changes, then a QRS is dropped without warning.

Third-degree (complete) AV block

P waves and QRS complexes are each regular, but have nothing to do with each other.

Sinus rhythm with first-degree AV block and PVCs

Two findings: a PR interval over 0.20 s on every sinus beat, and early wide beats with no P wave.

Sinus bradycardia with first-degree AV block

Two findings: a sinus rate under 60, and a PR interval over 0.20 s on every beat.

Supraventricular rhythms

They start in the atria, outside the SA node, so the QRS is narrow. Decided by regularity and by what the baseline looks like between complexes.

Atrial fibrillation

Irregularly irregular, with a wavy baseline and no P waves you can point to.

Supraventricular tachycardia (SVT)

Fast, narrow and perfectly regular. The P waves are buried.

Premature atrial contractions (PACs)

A beat that comes early, with a P wave of a different shape and a normal narrow QRS.

Atrial flutter

Sawtooth flutter waves at about 300 a minute, with a QRS after every third or fourth one.

Wolff-Parkinson-White pattern (pre-excitation)

A short PR interval, then a slurred start to a wide QRS: the delta wave.

Wandering atrial pacemaker

P waves of at least three different shapes, at a rate under 100.

Multifocal atrial tachycardia (MAT)

Irregular and faster than 100, with P waves of at least three different shapes.

Atrial fibrillation with PVCs

Irregularly irregular with no P waves, plus a wide beat or two that looks nothing like the rest.

Junctional rhythms

They start in the AV junction: a narrow QRS with no normal P wave in front of it. Decided by the rate.

Junctional rhythm

Narrow, regular, 40 to 60 a minute, with no P wave in front of the QRS.

Accelerated junctional rhythm

Narrow, regular, 60 to 100 a minute, with no P wave in front of the QRS.

Junctional tachycardia

Narrow, regular, faster than 100, with no P wave in front of the QRS.

Ventricular rhythms

They start in the ventricles, so the beat is wide and has no P wave. Decided by the rate, and by whether it is one beat or all of them.

Idioventricular rhythm

Slow, wide and regular, with no P waves. The ventricles are pacing themselves.

Ventricular tachycardia

Shockable if pulseless

Fast, wide and regular. Always check for a pulse.

Premature ventricular contractions (PVCs)

A beat that comes early and is wide, with no P wave and a T wave pointing the other way.

Ventricular bigeminy

Every other beat is a PVC: normal, wide, normal, wide.

Accelerated idioventricular rhythm (AIVR)

Wide and regular with no P waves, at 40 to 100: too fast for an escape rhythm, too slow for V-tach.

Torsades de pointes

A fast wide rhythm whose height swells and shrinks, as if twisting around the baseline.

Ventricular trigeminy

Every third beat is a PVC: normal, normal, wide.

Ventricular couplet (paired PVCs)

Two PVCs back to back, with no normal beat between them.

Ventricular triplet (three PVCs in a row)

Three PVCs in a row: the shortest run of ventricular tachycardia.

Multifocal PVCs

PVCs of more than one shape on the same strip, because they start in more than one place.

Paced rhythms

A pacemaker starts the beat. The pacing spike is the thing to find.

Ventricular paced rhythm

A sharp pacing spike, then a wide QRS, at a fixed rate.

Atrial paced rhythm

A pacing spike, then a P wave, then a normal narrow QRS.

AV sequential paced rhythm

Two pacing spikes per beat: one before the P wave and one before a wide QRS.

Pacemaker failure to capture

A pacing spike with no QRS after it.

Pacemaker failure to sense

Pacing spikes that land on the patient's own beats, where no pacing was needed.

Pacemaker failure to pace (failure to fire)

A paced rhythm with a pause in which there is no spike and no QRS.

Arrest rhythms

The patient has no pulse. Two are shockable and two are not, and that is the first thing to know about each.

Ventricular fibrillation

Shockable

Chaos. No P waves, no QRS complexes, nothing to measure.

Asystole

Not shockable

A nearly flat line. No electrical activity at all.

Pulseless electrical activity (PEA)

Not shockable

An organized rhythm on the monitor, but no pulse in the patient.

EKG rhythms comparison chart

The five-step read for every rhythm, side by side. Read across a row to describe a rhythm; read down a column to see which step separates two rhythms that look alike.

Rhythm	Rate	Regularity	P waves	PR interval	QRS
Normal sinus rhythm	60–100	Regular	1 per QRS	0.12–0.20 s	Narrow
First-degree AV block	Usually 60–100	Regular	1 per QRS	> 0.20 s, constant	Narrow
Second-degree type I (Wenckebach)	Atrial > ventricular	Grouped	More Ps than QRSs	Lengthens, then a drop	Narrow
Second-degree type II (Mobitz II)	Atrial > ventricular	Irregular at the drop	More Ps than QRSs	Constant, then a drop	Often wide
Third-degree AV block	Ventricular 20–60	Regular	Regular, unrelated to QRS	Never repeats	Narrow or wide
Atrial fibrillation	Variable	Irregularly irregular	None, wavy baseline	None	Narrow
SVT	150–250	Regular	Hidden	None	Narrow
Idioventricular rhythm	20–40	Regular	None	None	Wide
Ventricular tachycardia	Over 100	Regular	None	None	Wide
Ventricular fibrillation	Not countable	Chaotic	None	None	None
Asystole	0	None	None	None	None
PEA	Any	Organized	Any	Any	Any
Sinus bradycardia	Under 60	Regular	1 per QRS	0.12–0.20 s	Narrow
Sinus tachycardia	101–150	Regular	1 per QRS	0.12–0.20 s	Narrow
Sinus arrhythmia	60–100, varying	Irregular, gradual	1 per QRS	0.12–0.20 s	Narrow
Sinus arrest (pause)	Underlying sinus rate	Regular with a pause	1 per QRS, none in the pause	0.12–0.20 s	Narrow
Sinus rhythm with PACs	Underlying rhythm	Regular with an early beat	Early one looks different	Normal	Narrow
Atrial flutter	Atrial 250–350	Regular or variable	Sawtooth flutter waves	None	Narrow
Junctional rhythm	40–60	Regular	Absent or inverted	None or < 0.12 s	Narrow
Accelerated junctional rhythm	60–100	Regular	Absent or inverted	None or < 0.12 s	Narrow
Sinus rhythm with PVCs	Underlying rhythm	Regular with an early beat	None on the early beat	Normal on sinus beats	Early beat wide
Ventricular bigeminy	Count every QRS	Pairs: short, long	On every other beat	Normal on sinus beats	Alternates narrow, wide
Accelerated idioventricular (AIVR)	40–100	Regular	None	None	Wide
Torsades de pointes	200–250	Fast, twisting	None	None	Wide, changing
Paced rhythm	Set rate, 60–80	Regular	None	None; spike before QRS	Wide
Junctional tachycardia	Over 100	Regular	Absent or inverted	None or < 0.12 s	Narrow
Ventricular trigeminy	Count every QRS	Threes: normal, short, long	None on every third beat	Normal on sinus beats	Every third one wide
PVC couplet	Underlying rhythm	Regular with two early beats	None on the pair	Normal on sinus beats	Two wide in a row
PVC triplet (3-beat run of V-tach)	Underlying rhythm	Regular with a 3-beat run	None in the run	Normal on sinus beats	Three wide in a row
Multifocal PVCs	Underlying rhythm	Regular with early beats	None on the early beats	Normal on sinus beats	Wide, of different shapes
Atrial paced rhythm	Set rate, 60–80	Regular	Each after a spike	Normal, spike to QRS	Narrow
AV paced rhythm	Set rate, 60–80	Regular	Each after a spike	Fixed delay between two spikes	Wide
Failure to capture	Below the set rate	Regular with a missed beat	None	None; a spike with no QRS	Wide
Sinus rhythm with bundle branch block	60–100	Regular	1 per QRS	0.12–0.20 s	Wide, notched
Wolff-Parkinson-White (WPW)	60–100	Regular	1 per QRS	< 0.12 s	Wide, with a delta wave
Wandering atrial pacemaker	Under 100	Slightly irregular	3 or more shapes	Changes with the P wave	Narrow
Multifocal atrial tachycardia (MAT)	Over 100	Irregularly irregular	3 or more shapes	Changes with the P wave	Narrow
Failure to sense	The patient’s own rate	Underlying rhythm	Those of the underlying rhythm	Normal; spikes fall after the QRS	Narrow
Failure to pace	Below the set rate	Regular with a pause	None	None; no spike in the pause	Wide
Atrial fibrillation with PVCs	Count every QRS	Irregularly irregular	None, wavy baseline	None	Narrow, with wide PVCs
First-degree AV block with PVCs	Underlying sinus rate	Regular with early beats	None on the early beats	> 0.20 s on sinus beats	Narrow, with wide PVCs
Sinus bradycardia with first-degree AV block	Under 60	Regular	1 per QRS	> 0.20 s, constant	Narrow

Narrow means a QRS under 0.12 s (3 small squares); wide means 0.12 s or more. Rates are per minute. PEA is any organized rhythm in a patient with no pulse, so it has no pattern of its own.

Three questions that sort most strips

Is the QRS narrow or wide? Narrow means the impulse came from above the ventricles. Wide, with no P waves, means it started in the ventricles.
Is it regular? An irregular narrow rhythm with no P waves is atrial fibrillation. An irregular rhythm with P waves is usually a second-degree block.
Is there one P wave for every QRS, with the same PR interval? If yes, it is a sinus rhythm or first-degree block. If not, compare the PR intervals to find which block it is.

Built for rhythm-strip exams

Every rhythm in this library can be named from a single lead II strip, which is what a dysrhythmia exam puts in front of you. Each one is put through the same checks before it appears here; the method is on the about and methods page.

Try today’s three free strips

Where this comes from

The criteria and rules on this page are taken from published sources, and every strip is drawn to them and then measured by a separate program before it is shown. How the strips are made and checked

American Heart Association. CPR and Emergency Cardiovascular Care guidelines: adult cardiac arrest, bradycardia and tachycardia algorithms. Which rhythms are shockable, and the first actions for the arrest rhythms, slow rhythms and fast rhythms.
American Heart Association, American College of Cardiology and Heart Rhythm Society. Recommendations for the standardization and interpretation of the electrocardiogram, part I (Circulation, 2007). The paper every strip is drawn on: 25 mm per second and 10 mm per millivolt.
University of Arkansas. How to Interpret Rhythm Strips, in the open EKG Interpretation manual. The five-step read and the normal ranges for rate, PR interval and QRS.