Marathon Running Increases Your Risk Of A Heart Attack

I came across this fun article from Rodale Press supporting several facts and exposing a few myths regarding marathon running, exercise and general fitness.  Of particular interest was point number 6, that running a marathon increases your risk of a heart attack.

At first I thought, "I'm in big time trouble now".  Recently I've been running 4 hour long runs almost every week and the temperature over the last few weeks has been in the upper 80's and lower 90's.  So I know that there's some additional cardiac stress going on.