I don't think I understand. If they could rehabilitate unsuitable donor organs and didn't have to worry about rejection, there wouldn't be a shortage. Isn't that the end game?
No shortage is more like it. Intact cadaverous hearts are plentiful by comparison to awaiting heart transplant patients. Most heart failures are immediate and fatal, but people who have progressive failure are relatively rare. Transplant patients would conceivably be donors for the program (since most heart damage is soft tissue failure).