Some heart attacks go unrecognized
Yet "symptomless" does not mean "harmless."
In the movies, a heart attack victim often clutches his or her chest, falls to the floor, and dies on the spot. While this certainly can happen, symptoms can vary widely in type and intensity. In fact, up to 37% of people who have a heart attack never know it, because they never have symptoms. They find out they have had a heart attack when an electrocardiogram (ECG) is done for another reason.
A symptomless heart attack—often called a silent heart attack—is not harmless, however. A study published in the Sept. 5, 2012, issue of the Journal of the American Medical Association found that people with an unrecognized heart attack had the same risk of dying within five years as those who knew they'd had a heart attack. In both groups, the risk of dying during the five-year study was twice that of people who'd never had a heart attack.
Diagnosing a silent heart attack can be difficult. This study found that a magnetic resonance imaging (MRI) did a better job than electrocardiography in identifying silent heart attacks, likely because the areas of damage can be small. However, MRI is too expensive to use for routinely assessing people for silent heart attacks.