Very sad news. I thought this sort of stuff could be identified during a physical at the combine, per the quick article below.
http://blogs.nfl.com/2009/02/23/doct...ects-physical/
Raises an interesting ethical question. An enlarged heart, as far as I know, wouldn't be classified as life-threatening if discovered in a physical. But it's one thing for a borderline TE prospect to give up football in light of the news, quite another for a top 4 DE.
I guess the point's moot since the heart attack didn't occur while playing football.