"Silent" heart
attacks more common than thought
By Julie Steenhuysen
CHICAGO,19 april 2009- A study using new imaging technology found "silent" heart
attacks may be far more common, and more deadly, than suspected, U.S.
researchers said Friday.
Some studies estimate that these often painless heart attacks, also known
as unrecognized myocardial infarctions, affect 200,000 people in the
United States 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," Kim, whose study will appear
next week in the Public Library of Science journal PLoS Medicine, said
in a statement.
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, a marker for damaged
tissue.
But not all silent heart attacks result in Q-waves.
"
Those are the ones we haven't been able to count because we've never
had a good way to document them," Kim said.
To spot these, Kim and colleagues used a new type of magnetic resonance
imaging technology called delayed enhancement cardiovascular magnetic
resonance, which is especially adept at finding damaged heart tissue.
They studied 185 patients with coronary artery disease but no record
of heart attacks who were scheduled to have a test to look for possible
blockages in their heart arteries.
They found that 35 percent of the patients had evidence of a prior heart
attack. And they found that these so-called non-Q-wave heart attacks
were three times more common than silent heart attacks with Q-waves.
They also found that after two years of follow up, people who had suffered
a silent, non-Q-wave heart attack had an 11-fold higher risk of death
from any cause and a 17-fold higher risk of death due to heart problems,
when compared to patients who did not have any heart damage.
Kim said currently people who have had silent heart attacks are treated
like other patients with heart disease.
But given the findings, he said new studies should look at the best way
to care for these patients.
Heart disease is the No. 1 cause of death in the United States, followed
by cancer and stroke.
source |