ECG Rhythms......... without the Blues! - 3/5

1st December, 2006

Summary

Welcome back! So far in this series we’ve looked at normal ECG rhythms and ectopics.

In this issue we are going to look at two very common and potentially dangerous ECG rhythms called atrial fibrillation and atrial flutter


ATRIAL FIBRILLATION

Atrial Fibrillation (AF) is one of the most common arrhythmias that we see in clinical practice. It is particularly prevalent in the elderly population.

AF has been referred to as a ‘sheep in wolves clothing’ due to the potential complications associated with it. AF can cause or worsen heart failure and there is an increased risk of embolic complications such as stroke.

Atrial fibrillation can be chronic i.e. a permanent feature or it can also be paroxysmal where it occurs for short episodes (typically a few minutes) and ends spontaneously

In AF there is a lack of organized atrial activity as the atria typically discharge 400 - 600 random impulses every minute. This chaotic activity results in loss of atrial contraction causing the atria quiver of fibrillate.

The AV node is bombarded by this barrage of impulses and cannot conduct all of them to the ventricles - thankfully! Conduction to the ventricles is variable and can range from bradycardia to tachycardia.

When more than 100 atrial impulses are conducted to the ventricles this results in a ventricular rate of more than 100 beats per minute. We call this fast or uncontrolled atrial fibrillation. A ventricular rate of less than 100 is generally referred to as controlled atrial fibrillation.

Atrial Fibrillation may be seen as a consequence of the following :

  • Advanced age
  • Atrial enlargement
  • Alcohol
  • Myocardial Infarction
  • Heart Failure
  • Pulmonary embolism
  • Pericarditis
  • Idiopathic

What to look for on the ECG :

Atrial Fibrillation has the following ECG characteristics:

  • The rhythm is irregularly irregular
  • The heart rate can be variable and depends on how many atrial impulses are transmitted from the atria to the ventricles
  • There are no P waves
  • P waves are replaced by fibrillatory waves ~ f waves (look like squiggly lines!)
  • There are QRS complexes and T waves
  • P:QRS ratio is not applicable as we have no P waves
  • P-R interval is not applicable

See if you can spot these appearances on the following example of atrial fibrillation:

Rhythm strip showing Atrial Fibrillation
Fig 1: Atrial Fibrillation

Useful tip!
When you see an irregularly irregular rhythm without obvious P waves then there is a good chance you are looking at atrial fibrillation

Treatment for AF may include :

  • Anticoagulation due to risk of emboli
  • Drug therapy e.g.Digoxin to control the heart rate
  • Electrical cardioversion

ATRIAL FLUTTER

Atrial Flutter occurs when the atria discharge between 200 - 400 regular impulses every minute. This atrial activity results in P waves with a saw-tooth appearance. This is the most distinctive feature on the ECG. There are no isoelectric segments between the waves just a succession of flutter waves blending into one another

The ventricular response is normally slower and can occur regularly or irregularly. It is not uncommon for the ventricles to respond to every second atrial impulse. For example if the atrial rate were 300 then we would have a ventricular rate of 150. This is referred to as atrial flutter with 2:1 block

Atrial Flutter may be seen in the following circumstances:

  • Atrial enlargement
  • Drug effect e.g.Digoxin
  • Myocardial Infarction
  • Pulmonary embolism
  • Pericarditis

Atrial Flutter has the following characteristics:

  • The rhythm is usually regular but can be irregular
  • The heart rate can be variable and depends on how many atrial impulses are transmitted from the atria to the ventricles
  • There are no P waves
  • P waves are replaced by saw tooth flutter waves ~ F waves
  • There are QRS complexes and T waves
  • P:QRS ratio is not applicable as we have no P waves (but there may be a set ratio of flutter waves to QRS complexes e.g. 2:1)
  • P-R interval is not applicable

See if you can spot these appearances on the following example of atrial flutter:

Rhythm strip showing Atrial Flutter
Fig 1: Atrial Flutter

Useful tip!
The most common atrial rate in atrial flutter is 300 beats per minute and one of the most common conduction ratios to the ventricles is 2:1. This would result in a ventricular rate of 150 beats per minute.

Whenever you see a ventricular rate of exactly 150 beats per minute think atrial flutter!

Treatment for Atrial Flutter may include :

  • Anticoagulation due to risk of emboli
  • Drug therapy e.g.Digoxin to control the heart rate
  • Electrical cardioversion

 

Join us again in the next issue when we will examine the most serious ECG rhythms – those that can result in Cardiac Arrest.

In the meantime if you want to enhance your ECG skills then why not sign up for our new Online 12-Lead ECG Workshop programme. Available for only £25! For further details see the advert in this issue or visit our web site at www.cb-training.com.


Charles Bloe BSc RGN NDN ITU cert
Lead Lecturer and CEO - Charles Bloe Training Ltd

For more information on ECG Training visit www.cb-training.com