One, of course, must be declared brain dead, from some accident or other non-disease cause. They can keep the body ‘alive’ until the operation begins.....................
I remember reading a short Sci-fi story in the 1970s where a guy is put in suspended animation and awakes in the future. He's in a hospital room, where windows blow out due to Super Sonic jets taking off, and they are replaced immediately by an automated system. He starts talking to the man in the room with him.
After a short while the man in the room with him says that the man who awoke from suspended animation was being prepped for heart surgery.
The man, quite surprised, stated there was nothing wrong with his heart.
The man in the room tells him, "No, but there's something wrong with mine." and the story ends.