It happens time and again. A person feels a pain in the jaw, the arm, or the chest and passes it off as insignificant. He or she assumes the chest pain is indigestion or doesn't want the hassle of going to the hospital, assuming that wherever the pain is it will go away.

"The heart may develop enough malfunction that the patient develops shortness of breath," [Loh] said. "When the heart is not pumping enough, sometimes you feel pain, but there could be several moments before the pain."

Although pain is frightening and uncomfortable, it does tell a person that something is amiss. Up to 25% of people suffering a heart attack don't even feel the pain, Loh said. And those who do, don't necessarily feel it in their chests.