A newer, more selective blood thinner is safer, cheaper, and just as effective as the standard treatment used during a heart attack or to treat an impending one, according to a new study.

When a heart attack occurs, the coronary arteries are blocked and heart muscle is deprived of oxygen.

Clot busters dissolve a clot in a coronary artery and restore blood flow. Blood thinners don’t dissolve clots but prevent new clots from forming. They are given to help prevent further damage to dying heart muscles and to help restore their function. However, bleeding can be a complication of blood thinners.

The newer drug, known as Arixtra, could reduce by 80 percent the risk of dying due to serious bleeding, the major risk of blood thinners, says researcher Salim Yusuf, MD, chief of cardiology at McMaster University in Hamilton, Ontario.

The study pitted Arixtra against the traditional blood thinner Lovenox in 20,000 people with what doctors call acute coronary syndrome -- chest pain caused by a blocked heart artery that can cause a heart attack.

For every 1,000 people given Arixtra instead of Lovenox, 10 deaths or heart attacks, four strokes, and 25 major bleeds will be prevented, Yusuf tells WebMD.

“These are the people who, if not treated effectively, will die or suffer life-altering consequences,” says American Heart Association spokesman Timothy Gardner, MD. Gardner is a heart surgeon at the University of Pennsylvania in Philadelphia who was not involved with the research.

The findings were presented at the annual meeting of the European Society of Cardiology.

Researchers showed that the two blood thinners were equally effective at preventing heart attacks and deaths in the first 10 days after treatment.

But only 2 percent of those treated with Arixtra had major bleeding complications compared with 4 percent of those treated with Lovenox. That meant fewer transfusions to replace blood loss.

Thirty days after the treatment, there were 17 percent fewer deaths in those treated with Arixtra than in the other treatment group.

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Arixtra Works Earlier in Clotting Cascade

One of the reasons the newer medication may have the edge is its novel mode of action, the researchers say.

Clots are formed through a cascade of events. Arixtra appears to work at an earlier step in the formation of a clot.

Arixtra inhibits a protein critical to clot formation. In contrast, Lovenox works by combining with a protein in blood to prevent other proteins from working together to form a clot.

Gardnersays the newer drug “could have a tremendous impact” on the treatment of people with acute coronary syndrome.

“It’s a new type of drug in that it affects the clotting cascade earlier and doesn’t have the side effects” of the older medication, he tells WebMD. Nevertheless, he says further studies are needed to confirm the results before he would make the switch.

While “it looks safe, never say ‘never’ about pharmacological reactions,” he says.

But co-researcher Shamir Mehta, MD, also of Canada’s McMaster University, says the large study was as powerful as 10 smaller studies and doctors who are using Lovenox should think two or three times about whether they are doing the right thing.

Arixtra, which is already approved to prevent deep vein thrombosis -- life-threatening blood clots in the legs -- is also cheaper than standard treatment, he adds.

GlaxoSmithKline, which makes Arixtra, helped fund the trial; the company is a WebMD sponsor.

Coronary artery disease, also called coronary heart disease or heart disease, is a leading killer in the U.S., affecting more than 12 million Americans. It leads to heart attacks, angina, and acute coronary syndrome.

Know the warning signs of a heart attack such as chest discomfort, shortness of breath, or signs such as cold sweat, nausea, or lightheadedness. Call 911 immediately; don’t ignore the symptoms, and don’t wait longer than a few minutes before calling.

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By Charlene Laino, reviewed by Brunilda Nazario, MD

SOURCES: European Society of Cardiology Congress 2005, Stockholm, Sweden, Sept. 4-7, 2005. Salim Yusuf, MD, chief of cardiology, McMaster University, Hamilton, Ontario. Timothy Gardner, MD, professor of surgery, University of Pennsylvania, Philadelphia; spokesman American Heart Association. Shamir Mehta, MD, department of cardiology, McMaster University, Hamilton, Ontario. WebMD Medical Reference provided in collaboration with The Cleveland Clinic: “Heart Disease: Coronary Artery Disease.” American Heart Association.