EKG Rhythms and Their Practical Realities

From Normal Sinus Rhythm to Ventricular Fibrillation, here are the common rhythms a human will show on your EKG. For reference, all of the below rhythm strips are taken from Lead II.

 

When starting to interpret EKG rhythms for the first time, it helps to maintain a process of interpretation. To that end, for every rhythm here, we'll look at it in the same way:

 1 - Is it regular?

2 - Is it fast or slow?

3 - How many pacemakers are there?

4 - Is the QRS wide or narrow?

5 - Do all the beats look the same? Are some early, or is it chaos?

6 - Is there any other unique morphology?

Without further ado, and with thanks to the linked sources at the bottom of this page for the sample rhythm strips, let's begin:

Normal Sinus Rhythm [NSR]

This is normal! This is what you want to see.

With that in mind, is it...

  1. Regular? - Yes; another name for this rhythm is Regular Sinus

  2. Rate? - Normal, 60-100 in adults

  3. Pacemakers? - One, with an upright and rounded p-wave

  4. Wide or Narrow? - Narrow, with QRS generally less than 110mS

  5. Uniformity? - Yes, each p-wave matches to one QRS  complex and they're all the same

  6. Outliers? - No, unless there are ectopic beats [discussed below]

 

Sinus Tachycardia

Normal but fast

  1. Regular? - Yes

  2. Rate? - Fast, 100-150 in adults

  3. Pacemakers? - One, with an upright and rounded p-wave

  4. Wide or Narrow? - Narrow, with QRS generally less than 110mS

  5. Uniformity? - Yes, each p-wave matches to one QRS  complex and they're all the same

  6. Outliers? - No, unless there are ectopic beats

 

Sinus Bradycardia

Normal but slow

  1. Regular? - Yes

  2. Rate? - Slow <50-60, depending on local protocol

  3. Pacemakers? - One, with an upright and rounded p-wave

  4. Wide or Narrow? - Narrow, with QRS generally less than 110mS

  5. Uniformity? - Yes, each p-wave matches to one QRS  complex and they're all the same

  6. Outliers? - No, but ectopy may be present with slower rates

 

Sinus Arrhythmia

Normal but changes with breathing

  1. Regular? - No, but regularly irregular; rate increases with inspiration/other sources of increased chest pressure

  2. Rate? - VariesPacemakers? - One, with an upright and rounded p-wave

  3. Wide or Narrow? - Narrow, with QRS generally less than 110mS

  4. Uniformity? - Yes, each p-wave matches to one QRS  complex and they're all the same

  5. Outliers? - No, unless there are ectopic beats 

 

Sinus Pause

Sometimes the heart just needs a break

  1. Regular? - No, noticeable gaps between a T-wave and the next p-wave are present

  2. Rate? - Variable

  3. Pacemakers? - One, with an upright and rounded p-wave

  4. Wide or Narrow? - Narrow, with QRS generally less than 110mS

  5. Uniformity? - Yes, each p-wave matches to one QRS  complex and they're all the same, unless ectopic

  6. Outliers? - May have an escape beat [PAC/PJC/PVC] to terminate the pause and restore a regular rhythm

 

Atrial Fibrillation

Chaos that works

  1. Regular? - No; irregularly irregular rhythm

  2. Rate? - Said to be controlled for 60-100, uncontrolled >100

  3. Pacemakers? - A lot, with no clear single p-wave

  4. Wide or Narrow? - Narrow, with QRS generally less than 110mS

  5. Uniformity? - Only in the QRS complexes

  6. Outliers? - Hard to say because of p-wave irregularities, but junctional and ventricular ectopic beats are possible

 

Atrial Flutter

Sawtooth P-waves

  1. Regular? - Varies, can be either

  2. Rate? - Variable - suspect 1:2 A-flutter for rate of exactly 150, and 1:1 A-flutter with rate of exactly 300

  3. Pacemakers? - Usually one, look for sawtooth p-waves

  4. Wide or Narrow? - Narrow, with QRS generally less than 110mS

  5. Uniformity? - Only in the QRS complexes

  6. Outliers? - Hard to say because of p-wave irregular form, but junctional and ventricular ectopic beats are possible

  7. Clinical pearl - A-flutter always has a conduction ratio, of QRS:flutter wave [i.e. 1:1 means 1 flutter wave to each QRS complex; 1:4 means 4 flutter waves to each QRS complex]

 

Premature Atrial Complexes

PACs

  1. Regular? - N/A, ectopic single beats

  2. Rate? - N/A

  3. Pacemakers? - One, with a well-defined p-wave different than others present 

  4. Wide or Narrow? - Narrow, with QRS generally less than 110mS

  5. Uniformity? - Multiple PACs can be uniform or multiform depending on pacemaker sites in the heart - look for p-wave differences

  6. Outliers? - Yes they are

 

Superventricular Tachycardia

You should probably treat this

  1. Regular? - Yes

  2. Rate? - >150

  3. Pacemakers? - One in a re-entry tachycardia, without discernable p-waves

  4. Wide or Narrow? - Narrow, with QRS generally less than 110mS

  5. Uniformity? - Yes

  6. Outliers? - Very few if any

  7. Clinical Pearls - Vagal maneuvers can help slow or stop SVT; other forms of AV-nodal re-entry tachycardias [AVNRTs] are possible

 

Wandering Atrial Pacemaker 

This involves counting

  1. Regular? - Not usually

  2. Rate? - <100

  3. Pacemakers? - At least 3 different identifiable p-waves

  4. Wide or Narrow? - Narrow, with QRS generally less than 110mS

  5. Uniformity? - Each similar pacemaker and associate QRS complex is uniform to others of the same kind

  6. Outliers? - Hard to say because of p-wave irregularities, but junctional and ventricular ectopic beats are possible

Multifocal Atrial Tachycardia

More counting, but fast

  1. Regular? - Not usually

  2. Rate? - >100

  3. Pacemakers? - The same as WAP

  4. Wide or Narrow? - Narrow, with QRS generally less than 110mS

  5. Uniformity? - The same as WAP

  6. Outliers? - Hard to say because of p-wave irregularities, but junctional and ventricular ectopic beats are possible

  7. Clinical Pearl - MAT is tachycardic WAP!

Wolff-Parkinson-White Syndrome

A Triple D Threat

  1. Regular? - Can be, in a sinus rhythm; possibly not in a-fib

  2. Rate? - Dependent on underlying rhythm

  3. Pacemakers? - Usually one

  4. Wide or Narrow? - Narrow, with QRS generally less than 110mS, with slurred delta wave in P-R interval

  5. Uniformity? - Usually, yes

  6. Outliers? - Hard to say because of possible p-wave irregularities, but junctional and ventricular ectopic beats are possible

  7. Clinical Pearl - WPW represents the existence of a separate conduction pathway that bypasses the AV node. Because of this, symptomatic tachycardias with WPW cannot be treated with digoxin or diltiazem [high risk of conversion to VF] - DC cardioversion is the preferred treatment if any treatment is needed [and that's a big if]!

PJC.gif

Premature Junctional Complexes

PJCs

  1. Regular? - N/A, ectopic single beats

  2. Rate? - N/A

  3. Pacemakers? - One, with an inverted, retrograde, biphasic, or absent p-wave

  4. Wide or Narrow? - Narrow, with QRS generally less than 110mS

  5. Uniformity? - Multiple PJCs can be uniform or multiform depending on pacemaker sites in the heart - look for p-wave differences

  6. Outliers? - Yes they are

Idiojunctional Rhythm

Somewhere between good and bad

  1. Regular? - Yes

  2. Rate? - 40-60

  3. Pacemakers? - One, with an inverted, retrograde, biphasic, or absent p-wave

  4. Wide or Narrow? - Narrow, with QRS generally less than 110mS

  5. Uniformity? - Yes

  6. Outliers? - Possible, especially with slower rates that indicate lower physiological pacemaker sites

IJR.gif
Accelerated Junctional Rhythm 3.jpg

Accelerated Idiojunctional Rhythm

Faster this time

  1. Regular? - Yes

  2. Rate? - 60-100

  3. Pacemakers? - One, with inverted, retrograde, biphasic, or absent p-waves

  4. Wide or Narrow? - Narrow, with QRS generally less than 110mS

  5. Uniformity? - Yes

  6. Outliers? - Not without ectopic beats

Junctional Tachycardia

Slow it down a bit, eh?

  1. Regular? - Yes

  2. Rate? - >100 [but less than 150 for practical purposes]

  3. Pacemakers? - One, with inverted, retrograde, biphasic, or absent p-waves

  4. Wide or Narrow? - Narrow, with QRS generally less than 110mS

  5. Uniformity? - Yes

  6. Outliers? - If there are ectopic beats, then yes

JT.gif

Junctional Bradycardia

Too slow!

  1. Regular? - Yes

  2. Rate? - <40

  3. Pacemakers? - One, with inverted, retrograde, biphasic, or absent p-waves

  4. Wide or Narrow? - Narrow, with QRS generally less than 110mS

  5. Uniformity? - Yes

  6. Outliers? - Expect more ectopic beats as the rate slows

Ventricular Fibrillation

Chaos that fails

  1. Regular? - No; irregularly irregular rhythm

  2. Rate? - Rapid, from 150-500 or higher

  3. Pacemakers? - Near every ventricular cell is producing it's own signal

  4. Wide or Narrow? - No identifiable complexes to measure 

  5. Uniformity? - None

  6. Outliers? - No, this rhythm is the ultimate in cardiac chaos

  7. Clinical pearl - VF is one of the few cardiac rhythms that an AED will shock, and rightly so - it's guaranteed fatal without treatment. CPR and early defibrillation are key to survival.

VF.gif
VT.gif

Ventricular Tachycardia

You should definitely treat this

  1. Regular? - Yes

  2. Rate? - >100

  3. Pacemakers? - One

  4. Wide or Narrow? - Wide, with QRS generally > 110mS [high His Bundle rhythms may produce borderline-narrow complexes]

  5. Uniformity? - Almost always

  6. Outliers? - Possible, especially if fusion beats are present

  7. Clinical Pearl - VT is another AED-shockable rhtyhm. Without treatment, the perfusion from the ventricles will eventually fail. And your patient will die. 

Polymorphic Ventricular Tachycardia

This one's worse

  1. Regular? - No; irregularly irregular rhythm

  2. Rate? - >100

  3. Pacemakers? - One source, but the source moves in the ventricles

  4. Wide or Narrow? - Wide, >120mS

  5. Uniformity? - No, that's why it's called polymorphic

  6. Outliers? - Not unless you find fusion beats

  7. Polymorphic VT, of which Torsades-de-Pointes is the most well known, is the result of a potentially [but not likely] perfusing pacemaker in the ventricle that is moving between cells. Very rare overall, but when found, very often without a pulse. CPR and defibrillation are standards of treatment.

TdP.gif
PVC.gif

Premature Ventricular Compelxes

PVCs

  1. Regular? - No; irregularly irregular rhythm

  2. Rate? - Said to be controlled for 60-100, uncontrolled >100

  3. Pacemakers? - A lot, with no clear single p-wave

  4. Wide or Narrow? - Narrow, with QRS generally less than 110mS

  5. Uniformity? - Only in the QRS complexes

  6. Outliers? - Hard to say because of p-wave irregularities, but junctional and ventricular ectopic beats are possible

Idioventricular Rhythm

The last ditch regular pacemaker

  1. Regular? - Yes

  2. Rate? - <40

  3. Pacemakers? - One, in the ventricles - no p-wave 

  4. Wide or Narrow? - Wide, with QRS >120mS

  5. Uniformity? - Yes

  6. Outliers? - Weird ectopic beats may find their way through, all signs of a heart in last-ditch efforts to restore perfusion to the normal/higher pacemakers

IVR.gif
AIVR.gif

Accelerated Idioventricular Rhtyhm 

Now make it fast

  1. Regular? - Yes

  2. Rate? - 40-100

  3. Pacemakers? - One

  4. Wide or Narrow? - Wide, with QRS >120mS, though a pacemaker site near the junction in the Bundle of His will produce a more narrow waveform

  5. Uniformity? - Yes

  6. Outliers? - Possible as other pacemaker sites fire with restored perfusion

Asystole

He's dead, Jim!

  1. Regular? - Probably? Flat is flat. Agonal ventricular beats are possible, but not perfusing

  2. Rate? - Either 0 or infinity, depending on your answer to what 0/0 is. There's no cardiac activity here.

  3. Pacemakers? - None

  4. Wide or Narrow? - N/A

  5. Uniformity? - Flat lines all go together

  6. Outliers? - Agonal beats may be present in the early stages as various pacemakers fire their final beats

Asystole.gif

A Heart Block Says "What?"

When the SA node and the AV node don't communicate well, or when the electrical impulse gets jumbled and lost, the atria begin to beat separate from the ventricles. These are the four heart blocks:

1dHB.gif

First-Degree HB

When communication takes too long, we find a first-degree block

  • AV Node conduction slows

  • P-R interval >200mS

  • Still maintains sinus waveform with uniform p-waves

Second-Degree HB, Type I

When communication slows then stops, there you have a Wenckebach

  • AV conduction slows, then stops, then restarts

  • PR interval grows until a p-wave doesn't conduct to a QRS complex

  • The cycle can often repeat: long, longer, drop!, long, longer, drop!

  • Also called a Mobitz I Block

2dHB1.gif
2dHB2.gif

Second-Degree HB, Type II

When some p-waves don't get through, we call it a Mobitz II

  • AV Node conduction inconsistent

  • P-R interval usually >200mS

  • Some p-waves are not conducted through junction, but the ones that produce QRS complexes are regular and more-or-less uniform

Third-Degree HB

When P and Q can't agree, then they give us the third-degree

  • SA node still produces p-waves

  • No conduction through AV junction

  • P and QRS complexes are not associated - each has independent rate

  • Also known as Atrial-Ventricular dissociation or complete heart block

3dHB.gif