what causes u waves on ekg
This is known as a U wave. It is not very common and is easy to overlook. 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.