Is this artefact? - CardioScan Australia
Free Trial

Is this artefact?

By Assoc Prof Harry Mond
July 30, 2020

This week, I saw two similar unusual ECG appearances on consecutive days.

Is this artefact?

What do you think?

The pauses are real and there is a non-conducted atrial tachyarrhythmia, which terminates abruptly after a few beats.

I see similar appearances about once a month, so it is not rare.

I will show a few more examples:

Because it doesn’t conduct, the asystolic pauses can be quite long and symptomatic.

Why then, does the tachyarrhythmia stop abruptly?

Clue: Remember, my obsession with Wenckebach.

Some of you will say that is the reason…… and you would be correct!!!!!

This is one of the non-atrioventricular Wenckebach blocks.

Focal atrial tachycardia with Wenckebach block at the ectopic-myocardial junction.

In summary:

  • P waves are generated by impulses conducted to the atrium.
  • These ectopic tachyarrhythmias must pass an electrical barrier in order to depolarize the surrounding muscle.
  • The tachyarrhythmia eventually stops as there is a Wenckebach block sequence at this electrical barrier.
  • Rarely discussed in the literature.
  • The features of Wenckebach, as with sino-atrial block are
  • Must recognise footprints.


The footprint is the same as with sino-atrial Wenckebach (fun with ECGs 21):

The P to P cycle length shortens until there is block (red highlight).

Another example:

Can it occur in the ventricle? Of course!

A fast-short run of a tachyarrhythmia, with the last cycle length, being the shortest.

If you look you will find it!

Remember it’s all in the timing.

Harry Mond

About Assoc Prof Harry Mond

In 49+ years as a practicing cardiologist, Dr Harry Mond has published 260+ published manuscripts & books. A co-founder of CardioScan, he remains Medical Director and oversees 500K+ heart studies each year.

Download his full profile here.

View more
Clinical case studies Credentials Medical Papers Mobil-O-Graph myPatch Patient fact sheets