MONDAY, April 20 (HealthDay News) -- "Silent" heart attacks occur more often than previously believed and are associated with a high risk of premature death, according to a Duke University Medical Center study.

These silent heart attacks, also called non-Q-wave unrecognized myocardial infarctions (UMIs), often go undetected because they don't cause any pain and don't leave behind telltale irregularities that can be detected on electrocardiograms (EKGs).

"No one has fully understood how often these heart attacks occur and what they mean in terms of prognosis. 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," lead author and cardiologist Dr. Han Kim said in a Duke news release.

Kim and colleagues used delayed enhancement cardiovascular magnetic resonance (DE-CMR) to examine 185 patients who were believed to have coronary artery disease but had no record of any heart attacks.

The study found that 35 percent of the patients had evidence of a heart attack and that non-Q-wave attacks were three times more common than Q-wave UMIs. Non-Q-wave attacks were most common among those with more severe coronary artery disease.

The researches also found that over a two-year follow-up, patients who'd suffered non-Q-wave attacks had an 17-fold higher risk of death from heart problems and an 11-fold higher risk of death from any cause, compared to patients with no heart damage.

The study was published in the current issue of PLoS Medicine.

"Right now, there are no specific guidelines about how patients with UMIs should be treated," Kim said. "If patients with UMIs happen to be identified, they are usually treated similarly to those patients where heart disease has already been documented. Future studies will likely examine how common unrecognized non-Q-wave heart attacks are in other patient groups and how these UMIs should be treated."

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