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
ECG Ectopic atrial tachycardia inverted p waves

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
ECG Ectopic atrial tachycardia inverted p waves 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

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

Advanced Reading

ECG LIBRARY 700

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 |

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