Atrial Tachycardia – ECG

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.