DU Docs (or anyone else): Question about Robin Williams' heart condition and "Why"?

[Mike 03]

I'm interested in this case for a few reasons.

1. At 57 (I think) is he a bit young to have to have an aortic valve replacement?

2. He has both risk factors and preventative factors: by his own admission he was a cocaine user/addict for many years, but he also quit twenty years ago.

3. On the positive side, the guy was (or maybe still is) an endurance runner. My recollection is that he lived in Marin county and was known to run long distances almost every day.

As an aside, my physician once told me that I had an unusually large heart but that it was common for long-distance runners to have large hearts.

Do you think exercise can contribute to his condition? Do you think it's just genetics or something like that? Or could it be his early drug use?

I am asking these questions, of course, just in the nature of speculation, not as a diagnosis. And he's a public figure, so I figure it's okay to post these questions here.

Curious about your responses.