U waves

The 'U' wave is a wave on an electrocardiogram (ECG). It is the successor of the 'T' wave and may not always be observed as a result of its small size. 'U' waves are thought to represent repolarization of the Purkinje fibers. However, the exact source of the U wave remains unclear. The most common theories for the origin are:

In a normal heartbeat, the 'T' wave represents repolarization 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 fibers.

According to V. Gorshkov-Cantacuzene:

"The U wave is the momentum carried by the blood in the coronary arteries and blood vessels".

The resistivity of stationary blood is expressed as ${\displaystyle \left({\text{Ht}}\right)=|{\text{Ht}}\cdot (1+\alpha {\text{Ht}})}$, where ${\displaystyle \alpha }$ is a coefficient, and ${\displaystyle {\text{Ht}}}$ is the ; at that time, as during acceleration of the blood flow occurs a sharp decrease in the longitudinal resistance with small relaxation times.

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