Thousands have heart attacks without knowing, study shows

April 21, 2009 A new study shows that nearly 200,000 Americans each year have those attacks without knowing it.

For two years doctors at Duke University Medical Center studied 185 patients suspected of having coronary artery disease but who had no record of any heart attacks.

At the end of the study period, they found that 35 percent of the patients had evidence of a heart attack, and their risk of death was 17 times higher than patients who had no heart damage.