THURSDAY, May 26 (HealthDay News) -- Combining omega-3 fatty acids with blood-thinning drugs may reduce the risk of heart attacks in patients who've had stents placed in their coronary arteries, a new European study suggests.

While other research suggests that foods rich in omega-3s, including fatty fish such as salmon, help reduce the risk of heart problems in those with existing coronary artery disease, the new study is thought to be the first to look at the effect of the omega-3s on those treated with blood-thinning medications after stent placement.

In people with heart disease, a stent is a small tube placed in a coronary artery to keep it open and to allow the normal flow of blood and oxygen to the heart. But if a blood clot forms at the stent site, it can block blood flow and result in life-threatening problems such as a heart attack.

"Our results demonstrated improved clot properties and decreased thrombin [a clot promoter] formation after treatment with the fish oil capsules," wrote Dr. Grzegorz Gajos of John Paul II Hospital in Krakow, Poland, in the report.

Gajos and colleagues studied 54 patients, on average about 63 years old. They all had their clogged arteries opened by a catheter procedure. They then had stents inserted to keep the vessels open.

All were on the standard medical therapy used in these patients, including a daily dose of aspirin and an anti-platelet drug, clopidogrel (Plavix), for four weeks after the stent was installed.

Twenty-four patients were randomly assigned to receive a placebo pill daily and 30 patients received 1,000 milligrams of omega-3s (EPA and DHA) in pill form daily. The study was a double-blind, placebo-controlled trial -- meaning that neither the patients nor the researchers knew who was getting the omega-3s and who was getting the placebo (or sham treatment).

The researchers found that those who took the omega-3 fatty acids had improved clot properties and decreased clot formation after the treatment compared to the placebo group. The clots that formed in those on the fish oil pills, for example, were easier to disrupt.

The patients taking omega-3s not only produced less of the clot-promoting thrombin, their clots had larger pores and so were easier to break up. Clot destruction time in those patients was also 14.3 percent shorter than in the patients taking placebo pills.

Because there were not differences in other clotting features between the groups, the investigators felt that the finding indicated that the changes were due to the fish oil.

The researchers concluded that giving omega-3 fatty acids to patients who are stable after stent placement could improve outcomes, although they did not track outcomes for the patients in this study. Fish oil is not a replacement for the blood-thinner drugs or other treatments, they explained, but simply an adjunct (added) treatment.

However, the study authors pointed out that they could not extend the findings to other groups, such as those who are healthy, those with a high risk of coronary artery disease, or those not on the blood-thinning drugs. They are planning a larger study that will go on indefinitely, they added.

The study is published in the May 26 issue of Arteriosclerosis, Thrombosis and Vascular Biology: Journal of the American Heart Association.

The study is "trying to figure out why we might want to believe that omega-3 fatty acids have some benefit in this," said Dr. Kirk Garratt, clinical director of interventional cardiovascular research at the Lenox Hill Heart and Vascular Institute of New York, who was not involved in the study.

For the last 15 to 20 years, Garratt said, the benefits of fish oil have been debated. What the new study shows -- in a relatively small number of people -- is that if fish oil supplements are added to the usual medicine and medical care, "[scientists] find the scale has been tilted toward tearing down the clots rather than building up clots," he explained.

The study does not clarify exactly how the omega-3 fatty acids are affecting the blood clots, Garratt added, noting that the body is constantly making blood clots and that "there are forces that want to make clots and forces that want to tear them down." It is known, he said, that oxidative stress tilts the body toward formation of clots and makes it hard to tear them down. That would point to the antioxidant properties of fish oil getting the credit, he concluded.

The researchers found that giving the omega-3 fatty acids did not take away the body's inherent ability to make clots, he said, which is important to preserve.

If the antioxidants are responsible for affecting the blood clotting process, Garratt said, it could be they are revving up the body's ability to destroy clots.

What is not known, he said, is whether the findings mean that fish oil might help prevent heart attacks in these patients.

However, Garratt sees no reason to withhold fish oil from patients. "Fish oils have had more of a positive track record than negative track record," he said. High-potency fish oil affects blood fats favorably, he said, especially the triglycerides.

More information

To learn more about omega-3 fatty acids and the heart, visit the American Heart Association.