Im smellin a pool in the making here.... morbid as it sounds we got two people who passed with causes that may or may not B sketchy. Farrah does not count as that was pretty much writing on the wall and she was enjoying her last days with Ryan and family.
My two cents is MJ was a total junky courtesy of doctors addicitng him to pain meds, his $$$ and ability to get said drugs... very much like Elvis. As far as BIlly Mays I would suspect maybe what U said is right if not a combination of both; I think his family would have mentioned something about a pre-existing condition by now if they knew for sure. The other side of that is the list of things that can set a heart condition off, all the stress of his job, ect, ect... there could have been one or a combination of many factors that set this off.
I have a close family member with MVP, bad enough that it effects her everyday life and will eventually require full blown replacement valve heart surgery. Until the time in her life when the "deem it necessary for survival" there is always the remote chance she could "float a valve" and go into full blown cardiac arrest with very little chance of reversal.