Ischemia or ischaemia is a restriction in blood supply to any tissue,
muscle group, or organ of the body, causing a shortage of oxygen that is
needed for cellular metabolism (to keep tissue alive). Ischemia is generally
caused by problems with blood vessels, with resultant damage to or dysfunction
of tissue i.e. hypoxia and microvascular dysfunction. It also implies local
hypoxia in a part of a body resulting from constriction (such as
vasoconstriction, thrombosis, or embolism). Ischemia causes not only
insufficiency of oxygen, but also reduced availability of nutrients and
inadequate removal of metabolic wastes. Ischemia can be partial (poor
perfusion) or total blockage.