There are case reports of people with no previously known risks having a heart attack after a nightmare, though they appear to be quite rare. There are case reports of people with no previously known risks having a heart attack after a nightmare, though they appear to be quite rare. read more
And yes, if you have blockage(s) in your arteries/heart, and you have a nightmare, your blood flow increases because of being scared. And when you blood rushes through your body and can't get to your heart,--because of the blockages, yes it's possible to have a heart attack, while having a night mare. read more