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.

References

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