Multifocal Atrial Tachycardia

AKA “Chaotic atrial tachycardia”

Definition

  • A rapid, irregular atrial rhythm arising from multiple ectopic foci within the atria.
  • Most commonly seen in patients with severe COPD or congestive heart failure.
  • It is typically a transitional rhythm between frequent premature atrial complexes (PACs) and atrial flutter / fibrillation.

Electrocardiographic Features

  • Heart rate > 100 bpm (usually 100-150 bpm; may be as high as 250 bpm).
  • Irregularly irregular rhythm with varying PP, PR and RR intervals.
  • At least 3 distinct P-wave morphologies in the same lead.
  • Isoelectric baseline between P-waves (i.e. no flutter waves).
  • Absence of a single dominant atrial pacemaker (i.e. not just sinus rhythm with frequent PACs).
  • Some P waves may be nonconducted; others may be aberrantly conducted to the ventricles.

There may be additional electrocardiographic features suggestive of COPD.

Clinical Relevance

  • Usually occurs in seriously ill elderly patients with respiratory failure (e.g. exacerbation of COPD / CHF).
  • Tends to resolve following treatment of the underlying disorder.
  • The development of MAT during an acute illness is a poor prognostic sign, associated with a 60% in-hospital mortality and mean survival of just over a year. Death occurs due to the underlying illness; not the arrhythmia itself.

 Mechanism

Arises due to a combination of factors that are present in hospitalised patients with acute-on-chronic respiratory failure:

  • Right atrial dilatation (from cor pulmonale)
  • Increased sympathetic drive
  • Hypoxia and hypercarbia
  • Beta-agonists
  • Theophylline
  • Electrolyte abnormalities: Hypokalaemia and hypomagnesaemia (e.g. secondary to diuretics / beta-agonists)

The net result is increased atrial automaticity.

ECG Examples

Example 1

Multifocal atrial tachycardia:

  • Rapid irregular rhythm > 100 bpm.
  • At least 3 distinctive P-wave morphologies (arrows).

 

Example 2 

This ECG shows MAT with additional features of COPD:

  • Rapid, irregular rhythm with multiple P-wave morphologies (best seen in the rhythm strip).
  • Right axis deviation, dominant R wave in V1 and deep S wave in V6 suggest right ventricular hypertrophy due to cor pulmonale. 

 

Related Topics

Further Reading

Author Credits

References

  • Chan TC, Brady WJ, Harrigan RA, Ornato JP, Rosen P. ECG in Emergency Medicine and Acute Care. Elsevier Mosby 2005.
  • Surawicz B, Knilans T. Chou’s Electrocardiography in Clinical Practice (6th edition), Saunders 2008.
  • Wagner, GS. Marriott’s Practical Electrocardiography (11th edition), Lippincott Williams & Wilkins 2007.
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