MONDAY, Sept. 23, 2002 (HealthDayNews) -- Healthy relatives of people with severe coronary artery disease have the same kind of dense and tangled clots in their blood.
Although the exact relationship between the clots and future heart disease is not clear, "this does identify a potential risk factor [in the healthy relatives]," says Robert Ariëns, lead author of a study appearing in tomorrow's Circulation: Journal of the American Heart Association.
"The study is also giving us a bit more knowledge about how actual blocked clots occur in the blood stream and how structural features make it harder for clots to be broken down by the body's natural defense systems," adds Ariëns, a senior lecturer at the University of Leeds' Academic Unit of Molecular Vascular Medicine.
This may illuminate potential targets for new drug development.
Blood clots are made up of fibrin, an elastic, threadlike protein. Depending on various genetic and environmental factors, different clots can have different structures and functions, and can be more -- or less -- difficult for the body to break up on its own. Although dense fibrin clots have been found in people who already have heart disease, prior to this study, no one knew whether close relatives shared the same characteristics.
In this study, the researchers analyzed blood samples from 100 healthy men who were first-degree relatives of patients with severe heart disease. Those blood samples were then compared to 100 individuals who did not have a family history of heart disease.
Using scanning electron microscopy, the research team studied the thickness of the fibers and the fibrin structure. Turbidity analysis showed how fast the clots formed.
As it turned out, relatives of people with coronary artery disease had clots that formed quicker and were composed of thicker, denser fibers. The clots were less permeable than clots in members of the control group, making it more difficult for the body to dissolve them.
"What we now know is people who have heart attacks make clots that have the structural features that we see in relatives, only it's more pronounced in people with heart attacks," Ariëns explains. "Relatives are somewhere between the healthy controls and patients with regard to clot structure. It's much more pronounced in people who have had a heart attack, but the clots have structural features that are similar."
The different structure may explain why some patients don't respond to clot-busting drugs, says Dr. Robert Frankel of Maimonides Medical Center in Brooklyn, N.Y. "When you form the clot, it may be a more difficult clot, and we do have a subset of patients that get clot-busting drugs and fail," he says. "They may have a resistant clot because of the fibrin."
Further studies are needed to see if the clots found in the study will actually lead to future heart disease in the healthy family members. The clots do, however, seem to be a plausible mechanism leading to eventual coronary artery disease.
"Next, we're aiming to find out a little bit more about the molecular mechanisms that lead to this altered structure so that we can then find targets for the development of new drugs to interfere with the clot structure," Ariëns says. "We're only at the beginning, but this will hopefully lead to the development of new clot busters."
In the meantime, a regular infusion of low-dose aspirin, which decreases clotting in healthy people, may not be a bad idea for relatives of people with heart disease.
"Aspirin may counteract the effects on fibrin structure/function, but this may need further characterization in a study designed to investigate aspirin in relatives," Ariëns says.
What To Do
The American Heart Association has more information on blood clots. For more on drugs used to prevent blood clots in coronary artery disease, visit the University of California, Davis.
