Focal Atrial Tachycardia (FAT)

Definition

• 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

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

• Supraventricular tachycardia
• Atrial flutter
• Atrial fibrillation
• Accelerated Junctional Rhythm

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