Ischemia is the lack of adequate blood supply to tissues, e.g. to the heart muscle tissues. In the case of ischemia, the tissues are not getting enough oxygen. Reperfusion, then, is the damage caused to the tissues when the blood supply is restored to the tissue, and, suddenly, there is a re-oxygenation of the tissues as, for example, in cases of heart attack or heart surgery. Clinical studies have shown that pre-treatment and post-operative treatment with Coenzyme Q10 attenuates the extent of ischemia reperfusion injury.