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Cardiology Teaching Package

A Beginners Guide to Normal Heart Function, Sinus Rhythm & Common Cardiac Arrhythmias

The U Wave

Finally, it is possible to see another wave after the PQRST complex. This is known as a U wave. It is not very common and is easy to overlook. (see example below.)

Image: Image: U waves are indicated by the arrows

ECG displaying U waves

In a normal heart beat, the T wave represents repolarisation of the ventricles, specifically the repolarisation of the AV node and bundle branches. The U wave occurs when the ECG machine picks up repolarisation of the Purkinje fibres.

A "U wave" can also occur with electrolyte imbalances (potassium) but, again, this is not very common.

Authors Note:

I had never seen a naturally occurring U wave in 6 years in Cardiology, or maybe just never noticed. But, as fate would have it, when preparing this section I came across 3 patients with U waves on the same day.

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