Thanks ed34, for again helping me.
An area of dead tissue is just that, the tissue has died due to lack of oxygen for too long. Heart tissue, once past a certain stage of oxygen deprivation, will completely die and will not regenerate. Even if a tiny feed of blood has been reaching the tissue, there is a good chance most of it will recover over time. If the tissue is totally dead then there is no reason to restore blood flow to the area, it will never recover.