DALLAS, Jan. 8 -- The amount of a clot-dissolver protein circulating in the blood may be a good predictor of an elevated stroke risk, according to a study in this month's Stroke: Journal of the American Heart Association.
The clot dissolver, tissue plasminogen activator (TPA), is used as a treatment to stop heart attacks. TPA, which is produced naturally in the blood, keeps the clotting mechanism from running amok and clogging blood vessels throughout the body. Blood levels of a protein known as the TPA antigen reflect both free active TPA and predominantly bound inactive TPA.
Previous studies have shown that blood levels of the TPA antigen are associated with stroke risk in older men, says the study's co-author, Richard F. Macko, M.D., assistant professor in neurology and gerontology at the University of Maryland School of Medicine and the Veteran's Administration Medical Center in Baltimore.
"Our study's findings support the hypothesis that an impaired blood clotting mechanism characterized by increases in the TPA antigen is an important predictor for increased risk of stroke for individuals in our study," he says. The majority of TPA antigen exists as a complex with another protein, called plasminogen activator inhibitor, that inhibits its action. "Higher TPA antigen levels indicate higher levels of this inhibitor and lower levels of the active form of TPA," says Macko.
In the Stroke Prevention in Young Women Study, 59 women, age 16 to 44 years, who had a diagnosis of a first stroke, were matched with 97 women who had not had a stroke. The women were divided into four equal size groups depending on their blood level of TPA antigen. Those in the group with the highest blood levels of TPA antigen were nearly four times as likely to have suffered a stroke as women in the lowest-level group.
The study controlled for risk factors for stroke such as older age, high blood
pressure, cigarette smoking, body mass index (an indication of gir
Contact: Brian Henry
American Heart Association