Sir Ranulph Fiennes the explorer must be one of the fittest men on the planet, he's been in the SAS, he's run lots of marathons, climbed mountains and done expeditions like walking across Antarctica and so on (losing massive amounts of body weight in the process) yet amazingly he had a heart attack (and survived) aged 59.
The moral?- heart attacks can zap anybody no matter what kind of lifestyle you lead, so just stop worrying and eat, drink and be merry while you have the chance..