Heart and liver related apparently. That, to me at least, suggests some sort of prolonged steroid abuse could well be the cause.
Is that to say that they are dangerous? Hell no.
"Water" abuse can kill you, so as can "salt" abuse.
It's all about neglecting your health and being careless and foolish - IF that indeed was the case.
Personally never cared for the guy. Not into MMA nor his street 'bouts'.