I found a study which I posted in #20. The risk of sudden cardiac death in marathoners is lower than the general population. However, your condition of the structural change in the heart is drawing more attention not only in runners but in other high intensity training: biking, swimming; intense cross training, etc.
However, the risk of being a couch potato carries much more health risk...
Correct. It wasn’t exercise that was the problem, it was the long duration, high intensity, combined with a less than ideal diet, that caused the problem.