Atrial Tachycardia – ECG

Table of Contents

Table of Contents

Published February 2021

Maranda Herner, MD
Expert review – pending

Objectives

  1. Identify the key ECG findings for ectopic atrial tachycardia (AT) and use three key features to distinguish it from other supraventricular tachycardias (SVTs).

Teaching Instructions

Plan to spend 5-15 minutes familiarizing yourself with the ECG and relevant background information.  Have the image pulled up on the presenting screen or monitor.  Have one learner provide a systematic interpretation of the ECG.  If they do not do so on their own, prompt them to point out the distinguishing characteristics (abrupt, ectopic P wave) of this SVT. Then ask them to commit to a specific diagnosis.  Advance through the animations to highlight the abnormalities and final diagnosis.

Official ECG Read: Atrial tachycardia, originating at an ectopic focus that is near the SA node (note the upright p axis in II but not III compared to the native sinus p wave earlier and how the ectopic p wave of AT begins before the T wave has finished)

Clinical Diagnosis: Associated with atrial scarring (post-procedural), high catecholamine load, digoxin toxicity, congenital abnormalities, and idiopathic

Teaching: Atrial tachycardia (AT) is due to increased automaticity at an ectopic atrial focus other than the SA node.  AT may be difficult to differentiate from ST/flutter/AVRT/AVNRT at high HRs, but can be distinguished by the abrupt onset and non-sinus p wave that precedes the QRS.  The closer the ectopic focus is to the SA node, the more it looks like the native p wave, so an abrupt, rather than gradual, onset is key to differentiating the two.

ECG

Take Home Point

  1. Atrial tachycardia (AT) is due to increased automaticity at an ectopic atrial focus other than the SA node
  2. AT can be differentiated from ST/flutter/AVRT/AVNRT by the abrupt onset of a non-sinus p wave before the QRS.
  3. The closer the ectopic focus is to the SA node, the more it looks like the native sinus p wave, so abrupt onset is key to differentiating the two.

References

Goldberger, A. L., Shvilkin, A., Goldberger, Z. D. (2017). Clinical Electrocardiography: A Simplified Approach E-Book. United States: Elsevier Health Sciences.

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