ECG Infarction and Ischemia

The ST segment describes the delay between the end of the ventricular depolarisation (the QRS complex) and the beginning of ventricular repolarisation (the T wave). In other words, this is the gap between the electricity moving through the ventricles, and the ventricles returning to a position where they can be activated again. This is a refractory period, where the ventricles won't get set off by further electrical stimulation; it makes sure that the ventricles don't beat too quickly.