That's been answered. Endurance sports definitely cause heart issues.
I'd like to know more.
There's no reason one can't come back after a mild heart attack. As I said in another post, I've worked up from no stamina at all and bypass surgery to walking 15 miles a day. I don't run, though (my knees/feet wouldn't approve). I'll likely have to cut back over the next few weeks. I have things that I need to get done and my walking takes a lot of time.