Focal Atrial Tachycardia (FAT)
Definition
Focal atrial tachycardia (FAT) is a form of supraventricular tachycardia (SVT) originating from a single ectopic focus within the atria but outside of the sinus node
- The term FAT is commonly used synonymously with atrial tachycardia, a broader term referring to any form of SVT originating within the atria but outside of the sinus node
- FAT, atrial flutter and multifocal atrial tachycardia (MAT) are all forms of atrial tachycardia
- Management of the three types varies and thus distinguishing between them is clinically important
Pathophysiology of FAT
- Due to a single ectopic focus
- The underlying mechanism can involve increased automaticity, triggered activity or reentry
- May be paroxysmal or sustained
- Multiple causes including:
- Digoxin toxicity
- Atrial scarring due to ischaemic heart disease
- Catecholamine excess
- Stimulants including cocaine, caffeine
- Alcohol
- Congenital abnormalities
- Idiopathic
- Sustained atrial tachycardia may rarely be seen and can progress to tachycardia-induced cardiomyopathy
ECG Features of Atrial Tachycardia
- Atrial rate > 100 bpm
- Abnormal P wave morphology and axis (e.g. inverted in inferior leads) due to ectopic origin
- Unifocal, identical P waves
- Isoelectric baseline (unlike atrial flutter)
- Normal QRS morphology (unless pre-existing bundle branch block, accessory pathway, or rate-related aberrant conduction)
AV block may be present — this is generally a physiological response to the rapid atrial rate, except in digoxin toxicity where there is AV nodal suppression due to vagotonic effects of digoxin, resulting in a slow ventricular rate (“PAT with block”).
ECG Examples
Example 1
Focal atrial tachycardia:
- There is a narrow complex tachycardia at 120 bpm
- Each QRS complex is preceded by an abnormal P wave — upright in V1, inverted in the inferior leads II, III and aVF
- P wave morphology is consistent throughout
Example 2
Focal atrial tachycardia:
- There is a narrow complex tachycardia at 95 bpm
- Each QRS complex is preceded by an abnormal P wave — biphasic in V1; inverted in the inferior leads II, III and aVF; and inverted V3-V6
- P wave morphology is consistent throughout
Related Topics
References
- Poutiainen AM et al. Prevalence and natural course of ectopic atrial tachycardia. Eur Heart J. 1999 May;20(9):694-700
- Buttà C et al. Electrocardiographic diagnosis of atrial tachycardia: classification, P-wave morphology, and differential diagnosis with other supraventricular tachycardias. Ann Noninvasive Electrocardiol. 2015 Jul;20(4):314-27
Advanced Reading
Online
- Wiesbauer F, Kühn P. ECG Yellow Belt online course: Become an ECG expert. Medmastery
- Wiesbauer F, Kühn P. ECG Blue Belt online course: Learn to diagnose any rhythm problem. Medmastery
- Rawshani A. Clinical ECG Interpretation ECG Waves
- Smith SW. Dr Smith’s ECG blog.
Textbooks
- Mattu A, Tabas JA, Brady WJ. Electrocardiography in Emergency, Acute, and Critical Care. 2e, 2019
- Brady WJ, Lipinski MJ et al. Electrocardiogram in Clinical Medicine. 1e, 2020
- Straus DG, Schocken DD. Marriott’s Practical Electrocardiography 13e, 2021
- Hampton J. The ECG Made Practical 7e, 2019
- Grauer K. ECG Pocket Brain (Expanded) 6e, 2014
- Brady WJ, Truwit JD. Critical Decisions in Emergency and Acute Care Electrocardiography 1e, 2009
- Surawicz B, Knilans T. Chou’s Electrocardiography in Clinical Practice: Adult and Pediatric 6e, 2008
- Mattu A, Brady W. ECG’s for the Emergency Physician Part I 1e, 2003 and Part II
- 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
ECG LIBRARY
Electrocardiogram
Emergency Physician in Prehospital and Retrieval Medicine in Sydney, Australia. He has a passion for ECG interpretation and medical education | ECG Library |
MBBS (UWA) CCPU Emergency Medicine Advanced Trainee based in Melbourne, Australia. Co-author of the LITFL ECG Library. Likes Ultrasound, Echo, ECGs, and anything and everything with caffeine. Part of the 2021 ANZCEN Clinician Educator Incubator Programme | @rob_buttner | ECG Library |
“Both atrial flutter and multifocal atrial tachycardia are specific types of atrial tachycardia.” – is this correct?
If you’re using the term atrial tachycardia as synonymous with ectopic atrial tachycardia or focal atrial tachycardia then I don’t think this is right as atrial flutter is a distinct and separate entity.
Hi Luke,
Thank you for your comment. Atrial tachycardia is a broader term referring to any SVT initiated outside of the sinus node, and comprises FAT, MAT and atrial flutter. Atrial flutter is a separate entity to FAT but they are both forms of atrial tachycardia.
I hope this helps.
Rob