What is an explanation of ischemia?

Lack of enuff blood: "ischemia" = the normal tissue (eg heart, brain, intestine) is not receiving sufficient blood flow to supply the oxygen needed for the tissue's normal metabolic activity. For instance, ischemic heart muscle cannot contract normally. Cardiac ischemia is documented on a stress test, by using signs like EKG changes, flaccid heart muscle squeezing, or lack of uptake of nuclear tracer by heart muscle.

Depends: Low blood flow to tissue. Not enough oxygen delivered any organ with ischemia is probably not working well and the product of that organ diminished. Heart-low cardiac output kidney failure brain stroke limb gangrene.