“Ischemia” (pronounced “is-KEE-mee-uh”) means there’s not enough oxygen being delivered to a specific organ. “Infarction” means that part of the organ has already died, forever (usually). The most common place we hear the latter is “Myocardial Infarction,” i.e. a Heart Attack, part of the heart muscle is dead. But there’s also myocardial ischemia, causing chest pain although heart muscle is still holding its own. This, in medical terminology, is Angina Pectoris.
We often use the words for the brain as well. Cerebral infarction is a Stroke. Cerebral Ischemia looks like a stroke, but recovers (on its own, or by medical intervention). When it gets better on its own, we call it a “Transient Ischemic Attack,” or “TIA” (pronounced letter-by-letter). An MRI can identify a completed Stroke (i.e. Infarction). If the MRI is normal, but it looked or sounded like a stroke, it was just a TIA. That’s not so good, because the next time may be a permanent Infarction.
Mesenteric Ischemia and Infarction happen in the bowel, when blood supply gets cut off due to Atherosclerosis. If there’s Infarction, bowel tissue dies (called “necrosis”). That requires emergency surgery, before massive infection sets in from all the germs inside it.
Limb Ischemia means that an arm or leg has lost its circulation, often because of trauma, or occasionally some conditions. If blood supply isn’t restored, necrosis will occur, requiring surgical removal of muscle, and sometimes amputation.
And so on.