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Silent heart attacks more common than thought

April 20, 2009 |  5:00 pm

Heart People are often stunned when they undergo routine medical tests that reveal they -- unknowingly -- have had a heart attack. But a new study suggests that these silent attacks occur much more frequently than suspected and should be taken seriously.

A record of a heart attack, even the silent ones, can usually be found when a patient undergoes an electrocardiogram. Doctors look for the appearance of a specific alteration called a Q wave that signals the presence of damaged tissue. But the research reported today in the journal PLoS Medicine found that silent heart attacks, also called unrecognized myocardial infarctions or UMIs, occur that leave no telltale irregularities on ECGs.

Researchers from Duke University Medical Center looked for the frequency of heart attacks in 185 people with suspected heart disease but who had no record of heart attacks. Using an imaging technique called delayed enhancement cardiovascular magnetic resonance to look for damaged tissue, the researchers found 35% of the patients had evidence of a previous heart attack. Non-Q-wave heart attacks were three times more common than Q-wave heart attacks and were also more common among people with severe heart disease. Moreover, the study showed that people who had non-Q-wave silent heart attacks had a 17-fold higher risk of death due to heart problems compared with patients who did not have any heart damage.

"No one has fully understood how often these heart attacks occur and what they mean, in terms of prognosis," said Dr. Han Kim, the lead author of the study, in a news release. "With this study we can now say that this subset of heart attacks, known as non-Q-wave UMIs, is fairly common, at least among people with suspected coronary artery disease."

Kim, a Duke cardiologist, said that delayed enhancement cardiovascular magnetic resonance is a good method for detecting non-Q-wave heart attacks. More research is needed on how to treat patients with silent heart attacks, he said.

-- Shari Roan

Photo: "Fluttering Hearts," 1961 color lithograph. Credit: Norton Simon Museum Archives

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