Ischemia: not enough blood (=oxygen) supply to whatever was ischemic, usually the heart muscle, but can also be a limb, intestine, kidney, spleen etc. , but ischemic tissue isn’t dead (yet), if oxygen needs can be lowered the symptoms go away, e.g. patients having angina pectoris (ischemic heart pain) during exertion, which goes away after stopping exertion.

    Infarction: tissue that has died because of not getting enough oxygen containing blood: heart infarction AKA myocardial infarction, brain infarction, lung infarction, spleen infarction, kidney infarction, bowel infarction, placental infarction.