As did my father-in-law, in 1995, he went to bed "not feeling well" and never woke up. If he had went to the hospital and obtained a bypass I think he'd still be alive today in good health.
I seem to know frightening amount of folks who had just gotten clean bills of health from doctors only to either end up dying in their sleep (uncle) or even, worse, at work (a couple of folks I knew). Very unexpected, but quiet departures...