(AP) - For the first time, researchers have linked the hardening of arteries to blood clots in veins, a finding that could trigger new research in the effort to prevent the blockages that kill thousands of people each year.
Italian researchers found patients hospitalized with unexplained deep-vein clots were nearly 2 1/2 times more likely to also have hardening of the arteries, or atherosclerosis, than patients with deep-vein clots attributed to other health problems.
The doctors concluded either hardening of the arteries can induce blood clots in veins or the two conditions share common risk factors.
"I favor the first hypothesis," said Dr. Paolo Prandoni, the lead researcher and an associate professor of internal medicine at the University of Padua Medical School.
Prandoni said scientists had not suspected the link. He said researchers now should study mechanisms that might connect artery and vein disorders, and whether cholesterol-lowering or anti-clotting drugs can prevent deep-vein clots as well as control atherosclerosis to prevent heart attacks and strokes.
The study was reported in Thursday's edition of the New England Journal of Medicine.
Arteries, which carry blood from the heart throughout the body, can harden over time from factors including smoking, high blood pressure and cholesterol, or plaque, which stays in arteries and attaches to their walls.
Veins, which have thinner walls, don't harden or build up plaque. But blood clots can form in veins from surgery, cancer, leg injury or immobilization, pregnancy, recent childbirth or use of the hormone estrogen. In about one-third of patients with a vein clot, there's no identifiable reason - and thus no way to prevent it.
If part of a clot breaks free, it can travel to the lungs and lodge there, causing a blockage called a pulmonary embolism. Pulmonary embolisms kill at least 60,000 Americans annually, according to the Centers for Disease Control and Prevention; one apparently killed NBC war correspondent David Bloom on Sunday.
Dr. Sidney Smith, past president of the American Heart Association, said Prandoni's study must be repeated on more patients. Rather than atherosclerosis causing deep-vein clots, or thrombosis, he thinks the two conditions have the same risk factors - standard causes of heart disease such as smoking, high blood pressure and high cholesterol.
"We need to understand how the risk factors that contribute to atherosclerosis might also contribute to heightened thrombosis," said Smith, who directs the Center for Cardiovascular Science and Medicine at University of North Carolina-Chapel Hill.
Doctors know patients with hardened arteries have more blood clots in their arteries than other people, probably because of platelets clumping together too much, Smith said. But this is the first report of patients with atherosclerosis having vein clots.
"From a basic science perspective, it makes sense," said Carl Hock, acting chairman of the cell biology department at the University of Medicine and Dentistry of New Jersey-Stratford.
He suggested the link may be endothelial cells, which line blood vessels and release substances that prevent clotting. The cells function abnormally in patients with both atherosclerosis and deep-vein clots.
Atherosclerosis is the main underlying cause of heart disease, which kills about 13 million Americans annually. Meanwhile, there are 200,000 to 600,000 new cases of vein clots each year.
The study included 449 patients hospitalized from March 1996 to April 2001. Two-thirds had deep-vein clots but no symptoms of atherosclerosis; the other third were a comparison group with unrelated conditions.
Each was given an ultrasound of the arteries in the neck called carotid arteries to spot plaque, an indicator arteries throughout the body are hardening, and doctors determined whether there was a clear clause for the 299 patients with vein clots.
Smith said controlling cardiac risk factors through smoking cessation, taking a daily baby aspirin, getting more exercise and losing weight would slow progression of atherosclerosis and might also prevent or limit vein clots.
The study is "one more reason that patients ought to understand whether they're at risk for heart disease and take steps to lower those risk factors," Smith said.
In some cases, risk factors and symptoms such as chest pain or shortness of breath could warrant expensive imaging tests to detect buildup of plaque indicating a patient's arteries have hardened - and that medication or more aggressive treatment is needed.
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