The<unk>  is a measurement made on an electrocardiogram used to assess some of the electrical properties of the heart. It is calculated as the time from the start of the Q wave to the end of the T wave, and approximates to the time taken from when the cardiac ventricles start to contract to when they finish relaxing. An abnormally long or abnormally short<unk>  is associated with an increased risk of developing abnormal heart rhythms and sudden cardiac death. Abnormalities in the<unk>  can be caused by genetic conditions such as long<unk>  syndrome, by certain medications such as sotalol or pitolisant, by disturbances in the concentrations of certain salts within the blood such as hypokalaemia, or by hormonal imbalances such as hypothyroidism.
QT interval
PR interval
QRS complex
P wave 
T wave
ST segment
J wave
Plateau potentials