Atrial Tachycardia

AKA paroxysmal atrial tachycardia (PAT), unifocal atrial tachycardia, ectopic atrial tachycardia

Background

  • 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.

Pathophysiology

  • 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

  • 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 Example

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.

Related Topics

Further Reading

Author Credits

References

  • Surawicz B, Knilans TK. Chou’s Electrocardiography in Clinical Practice. 6th Edition. Saunders Elsevier 2008.
  • Chan TC, Brady WJ, Harrigan RA, Ornato JP, Rosen P. ECG in Emergency Medicine and Acute Care. Elsevier Mosby 2005.
  • Brady WJ, Truwit JD. Critical Decisions in Emergency & Acute Care Electrocardiography. Wiley Blackwell 2009.
  • Poutiainen AM, Koistinen MJ, Airaksinen KE, Hartikainen EK, Kettunen RV, Karjalainen JE, Huikuri HV. Prevalence and natural course of ectopic atrial tachycardia. Eur Heart J. 1999 May;20(9):694-700. PMID: 10208790
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Comments

  1. Fazle Rabbi says

    Excellent work Dr. Edward. The explanation of ECG in accordance with pathophysiology is really helpful. I was just curious to know whether the P waves in Atrial Tachycardia will appear in a regular fashion following regular interval or they will appear irregularly? I understand their morphology will be changed, but what about their intervals?

    Thanks again.

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