Atrial Tachycardia

Atrial Tachycardia Overview

Atrial tachycardia is a form of supraventricular tachycardia, originating within the atria but outside of the sinus node. Both atrial flutter and multifocal atrial tachycardia are specific types of atrial tachycardia.

AKA: Paroxysmal Atrial Tachycardia (PAT), unifocal atrial tachycardia, ectopic atrial tachycardia

Pathophysiology of Atrial Tachycardia

• Usually due to single ectopic focus.
• The underlying mechanism can involve reentry, triggered activity or increased automaticity.
• May be paroxysmal or sustained.
• Multiple causes including digoxin toxicity, atrial scarring, catecholamine excess, congenital abnormalities; may be idiopathic.
• Sustained atrial tachycardia may rarely be seen and can progress to tachycardia-induced cardiomyopathy

ECG Features of Atrial Tachycardia

• Atrial rate > 100 bpm.
• P wave morphology is abnormal when compared with sinus P wave due to ectopic origin.
• There is usually an abnormal P-wave axis (e.g. inverted in the inferior leads II, III and aVF)
• At least three consecutive identical ectopic p waves.
• QRS complexes usually normal morphology unless pre-existing bundle branch block, accessory pathway, or rate related aberrant conduction.
• Isoelectric baseline (unlike atrial flutter).
• AV block may be present — this is generally a physiological response to the rapid atrial rate, except in the case of digoxin toxicity where there is actually AV node suppression due to the vagotonic effects of digoxin, resulting in a slow ventricular rate (“PAT with block”).

ECG Examples

Example 1

Ectopic 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.

Example 2

Ectopic 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

Related Topics

• 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. PMID: 10208790

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

Advanced Reading

• Brady WJ, Truwit JD. Critical Decisions in Emergency and Acute Care Electrocardiography
• Surawicz B, Knilans T. Chou’s Electrocardiography in Clinical Practice: Adult and Pediatric
• Wagner GS. Marriott’s Practical Electrocardiography 12e
• Chan TC. ECG in Emergency Medicine and Acute Care
• Rawshani A. Clinical ECG Interpretation
• Mattu A. ECG’s for the Emergency Physician
• Hampton JR. The ECG In Practice, 6e