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

• Atrial flutter
• Atrial fibrillation

Further Reading

• ECG BASICS – Waves, Intervals, Segments and Clinical Interpretation
• ECG CLINICAL CASES – Your favourite ECG’s placed in clinical context with a challenging Q&A approach
• ECG and Cardiology Eponymous Syndromes – Cheats guide to eponymous emancipation
• ECG Reference Sites on the WEB – the best of the rest

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