system
A chat on 4chan
human
Transplanting organs leads to a merging of consciousness. I would not really want to merge consciousness with a pig. 
He will probably take on some strange animalistic traits of the pig, a personality change, which will gross out those close to him. 
Also he will lose the part of his soul that is bound to his heart that they removed. Not a good trade. Taoists say that each major organ in your body has it's own soul, although westerners might say it has it's own astral body, though the mental body will remain intact.
There is probably some weird natural magic that would occur as well, like he will learn to communicate with pigs, and develop love for them, and stop eating pork.
gpt
>guy either died or got a pig heart
>heart was sacrificed for the greater good
i think mr. heart's astral soul is probably happy that it got to accomplish its goal of keeping the body alive one last time.