Aug. 16, 2001 DALLAS, Aug. 14 – High blood levels of “free” fatty acids may be associated with abnormal heartbeats that can lead to sudden death in middle-aged men, according to a report in today’s Circulation: Journal of the American Heart Association.
“This the first long-term study to find that high levels of free fatty acids may be linked to an increased risk of sudden death in healthy men,” says study author Xavier Jouven, M.D., Ph.D., from the division of cardiology at Hôspital Européen Georges Pompidou in Paris. Researchers have known that high levels of free fatty acids could trigger irregular heart rhythms in individuals with heart disease, but no one had studied whether they also can be dangerous for someone who is healthy, he says.
Fats that we eat are stored in adipose (fat) tissue. When these fats are released from their storage sites, they become circulating nonesterified fatty acids (NEFA), or free fatty acids.
While this study shows an association between circulating levels of free fatty acids and a high risk of sudden cardiac death, an accompanying editorial says that not all fatty acids are equal in their propensity to cause arrhythmias. The editorial suggests that increasing omega-3 fatty acids in the diet, which come from fatty fish or canola oil, and decreasing the intake of omega-6 fatty acids, found in plant seed oils (corn, safflower, sunflower), is a way to reduce the risk of sudden death.
Jouven and his colleagues enrolled 5,250 French civil servants in the Paris Prospective Study between 1967 and 1972 and followed them for an average of 22 years. Study participants were men between the ages of age 42 and 53 at the time of enrollment. The blood samples analyzed in the current research were taken one year after enrollment.
After researchers adjusted for age, heart rate, tobacco consumption, blood pressure and other factors, NEFA levels appeared to be a risk factor for sudden cardiac death. The risk of sudden death increased as levels of NEFA increased, but no such relationship was found for fatal heart attack. Very high levels (407 micromoles per liter or more) indicated a greater than 30 percent risk of sudden cardiac death. Sudden cardiac death, sometimes called cardiac arrest, may occur as a complication of a heart attack, usually within one to two hours after the beginning of heart attack symptoms. It can occur independent of a heart attack, although underlying blood vessel disease is usually present. One cause of sudden death is ventricular fibrillation, in which the heart contracts in a fast and chaotic rhythm that makes it unable to pump blood to the rest of the body. Heart attack survivors are at increased risk of sudden death, as are people with diabetes or a family history of sudden death.
In his report, Jouven references a heart attack study in which patients were given a substance that reduced circulating NEFA and showed a decrease in the occurrence of ventricular arrhythmia.
“Although its clinical benefit is not yet proven, finding ways to decrease free fatty acid levels in subjects at high risk for sudden death may be a target for prevention,” he says.
Jouven says further studies are needed to assess the potential of using NEFA measurement for the prediction of sudden death, and of using NEFA levels as a possible target for preventing sudden death.
A number of factors including cigarette use, fasting, diabetes, hyperthyroidism or heart attack can trigger the release of fatty acids from adipose tissue. Alexander Leaf, M.D., author of an editorial that accompanies Jouven’s report, believes that some of these fatty acids can cause fatal arrhythmias when released from storage, while others may be protective.
Leaf, a professor of clinical medicine at Harvard Medical School, says that high levels of omega-6 fatty acids may encourage arrhythmias if their levels aren’t balanced by omega-3 fatty acids.
“Only relatively small amounts of omega-3 fatty acids seem needed for protection, but the intake must be accompanied by a reduction of omega-6 fatty acids to reach closer to a 1-1 ratio of omega-6 to omega-3 polyunsaturated fatty acids,” he says.
“The findings of Jouven and co-authors suggest that the subjects included in the Paris Prospective Study were probably consuming diets low in omega-3 fatty acids, as has been the case during the past century in Western industrialized countries,” according to Leaf.
Last October, the American Heart Association revised its dietary recommendations to include advice to eat two meals of fatty fish – those highest in omega-3 fatty acids – per week. The new dietary guidelines also emphasize the importance of an overall dietary pattern, focused on fruits, vegetables, whole grains, low-fat dairy products and fish, lean meats and poultry, rather than a tight focus on reducing one dietary component, such as fat.
Co-authors include Marie-Aline Charles, M.D.; Michel Desnos, M.D.; and Pierre Ducimetière, Ph.D.
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