Multifocal Atrial Tachycardia (MAT)

Multifocal Atrial Tachycardia (MAT) Overview

• 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.

AKA “Chaotic atrial tachycardia”

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

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

• The ECG in COPD
• Right atrial enlargement (P pulmonale)
• Right ventricular hypertrophy

Advanced Reading

Online

• Wiesbauer F, Kühn P. ECG Mastery: Yellow Belt online course. Understand ECG basics. Medmastery
• Wiesbauer F, Kühn P. ECG Mastery: Blue Belt online course: Become an ECG expert. Medmastery
• Kühn P, Houghton A. ECG Mastery: Black Belt Workshop. Advanced ECG interpretation. Medmastery
• Rawshani A. Clinical ECG Interpretation ECG Waves
• Smith SW. Dr Smith’s ECG blog.

Textbooks

• Zimmerman FH. ECG Core Curriculum. 2023
• Mattu A, Berberian J, Brady WJ. Emergency ECGs: Case-Based Review and Interpretations, 2022
• Straus DG, Schocken DD. Marriott’s Practical Electrocardiography 13e, 2021
• Brady WJ, Lipinski MJ et al. Electrocardiogram in Clinical Medicine. 1e, 2020
• Mattu A, Tabas JA, Brady WJ. Electrocardiography in Emergency, Acute, and Critical Care. 2e, 2019
• Hampton J, Adlam D. The ECG Made Practical 7e, 2019
• Kühn P, Lang C, Wiesbauer F. ECG Mastery: The Simplest Way to Learn the ECG. 2015
• Grauer K. ECG Pocket Brain (Expanded) 6e, 2014
• Surawicz B, Knilans T. Chou’s Electrocardiography in Clinical Practice: Adult and Pediatric 6e, 2008
• Chan TC. ECG in Emergency Medicine and Acute Care 1e, 2004

LITFL Further Reading

• ECG Library Basics – Waves, Intervals, Segments and Clinical Interpretation
• ECG A to Z by diagnosis – ECG interpretation in clinical context
• ECG Exigency and Cardiovascular Curveball – ECG Clinical Cases
• 100 ECG Quiz – Self-assessment tool for examination practice
• ECG Reference SITES and BOOKS – the best of the rest