'Silent' heart attacks quite common: study A study using new
imaging technology has found 'silent' heart attacks may be far
more common, and more deadly, than suspected, say US
researchers. Some studies estimate that these often painless
heart attacks, also known as unrecognised myocardial
infarctions, affect 200,000 people in the United States and
300,000 in Europe each year. But Dr Han Kim of Duke University
in North Carolina suspects the numbers may be far higher. "No
one has fully understood how often these heart attacks occur and
what they mean, in terms of prognosis," says Kim, whose study
will appear in the Public Library of Science journal PLoS
Medicine. Doctors usually can tell whether a patient has had a
recent heart attack by looking for signature changes on a test
of the heart's electrical activity called an electrocardiogram,
and by checking for certain enzymes in the blood. For a heart
attack that might have occurred in the past, doctors look for
changes on an electrocardiogram called a Q-wave,