The heart, once damaged cannot be healed. It can be replaced. It can be supported. but it doesn't heal. That is what I have read.
You know the have treatments going on, that if he can be kept alive and going, not stressed and keep him at a level his heart can handle perhaps they will be made available in a short time. They can regrow almost anything they say.
Look at biden. He got a whole new head.
The brain is another one that doesn't heal up.
Look again at biden.