The amount of a clot-dissolver protein circulating in the blood may be a good predictor of high stroke risk, according to a study in this month's Stroke: Journal of the American Heart Association. The clot dissolver, TPA (tissue plasminogen activator), is used as a treatment to stop heart attacks. TPA, which is produced naturally in the blood, keeps the clotting mechanism from running wild and clogging blood vessels throughout the body. Blood levels of a protein known as the TPA antigen measure TPA as well. Blood levels of the TPA antigen show stroke risk in older men, says the study's co-author, Richard F. Macko, MD. "Our study's findings support the hypothesis that an impaired blood clotting mechanism as shown by increased TPA antigen predicts increased risk of stroke," he says. Most TPA antigen exists as a complex with another protein, called plasminogen activator inhibitor, that reduces its action. "Higher TPA antigen levels indicate higher levels of this inhibitor," 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 4 groups depending on their blood level of TPA antigen. Those in the group with the highest blood levels of TPA antigen were 4 times as likely to have a stroke as women in the lowest-level group. Macko cautions that more studies are needed to see if a patient's TPA antigen blood level is a good predictor of stroke risk. Title: Elevated Blood Levels Of Inactive TPA Linked to Increased Stroke Risk in Young Women From: Stroke: Journal of the American Heart Association January 7, 1999 ----------------------- Researchers say an MRI can tell which heart-disease patients are at high risk for heart attack and stroke. In several small trials, MRI (magnetic resonance imaging) identified the type of coronary plaque that is most likely to rupture. About 30% to 50% of these plaques may rupture, causing a heart attack or stroke. By adding more sophisticated software and hardware to the standard MRI, researchers at the Mt. Sinai School of Medicine iedntified plaque type in the aortas of 11 patients. Although MRI has been used to iedntify plaque type in carotid arteries, none of the current techniques, such as ultrasound or TEE (transesophageal echocardiography), have enough accuracy to look at the vessel wall, according to lead researcher Zahi A. Fayad, MD. Plaque composition was checked using proton density and T2-weighted images transverse to the thoracic aorta, which allowed researchers to detect aortic plaque type and maek-up along the entire aorta. Valentin Fuster, MD, president of the American Heart Association, compared this technique to an X-ray, in which the doctor can see a fixed image of the artery even though the heart is in motion. However, he cautioned, MRI is a sensitive technique that should be performed by skilled technicians for a proper analysis. In a second study, catheter-based MRI was used to tell the difference between types of plaque in arteries. The researchers extracted and analyzed the plaques of 19 human carotid endarterectomy specimens and used several different MRI image properties to test their properties. They found that catheter-based MRI can identify different types of plaque. "The most significant clinical advance of the next 5-10 years will be the ability to diagnose dangerous plaques," said Jan Breslow, M.D., a Frederick Henry Leohnhardt Professor at Rockefeller University. During that time, Dr. Rogers said, understanding plaque composition may lead to preventive therapies. In a third study, researchers used near-infrared spectroscopy to analyze 32 post-mortem human aorta tissue samples. The technology used is similar to that used to determine the chemical composition of rocks on Mars, said James E. Muller, MD. Dr. Muller and his team think this technology could be used via a catheter to examine coronary arteries in living patients. If the results of these studies are confirmed by larger trials, Dr. Breslow said, then MRI "may become an important diagnostic test in the future." Dr. Fuster cautioned that a positive scan does not absolutely mean a stroke or heart attack will happen, adding that all the patients in these studies already had known problems. The goal is to be able to screen patients without symptoms who may be at risk, he said. Title: Non-Invasive Techniques Can Identify Vulnerable Plaque From: Internist & Cardiologist Edition v39.n21:4, 1998 By: Samantha Meese ---------------------- National Heart, Lung, and Blood Institute (NHLBI)-supported scientists say that ultrasonography predicts risk of heart attack and stroke in older persons with no heart disease symptoms. The test measures the thickness of the walls of 2 arteries in the neck. "This study shows that ultrasonography has potential in preventing heart attack and stroke," said NHLBI Director Dr. Claude Lenfant. "By identifying high risk patients, ultrasonography would allow doctors to give aggressive treatment early." Such treatment includes control of high blood pressure and high cholesterol, weight loss, exercise, and aspirin and other drug therapies. Each year about 160,000 Americans die from stroke. One in five Americans has some form of heart disease. Ultrasonography is a relatively inexpensive, painless test in which sound waves above the range of human hearing are sent into the neck. Echoes bounce off the moving blood and the tissue in the artery and are then formed into an image. The test is currently used in stroke prevention to diagnose advanced disease in the carotid arteries. The study involved 4,476 men and women, aged 65 and older, from the Cardiovascular Health Study (CHS), a multi-center study of older Americans. About 40% of participants were men and 60% women. About 15% were black and the rest were white. Participants were followed-up for 6 years. Scientists used ultrasound to measure wall thickness in the common and internal carotid arteries. With atherosclerosis, fat and cholesterol are deposited in artery walls. The walls thicken and become less flexible, and the narrowed opening erduces blood flow. If an artery becomes blocked, a heart attack or stroke can happen. This buildup is not uniform. By combining the measures from both arteries, a more complete picture of the patients' conditions was formed. Patients' risk of heart attack and stroke increased in direct proportion with the thickness of their artery walls. Those with the thickest arteries had 5 times greater risk of heart attack or stroke than those with the thinnest measurements. Dr. Daniel O'Leary, Radiologist-in-Chief, Department of Radiology, Tufts New England Medical Center (NEMC), and Dr. Teri Manolio, Director of the Epidemiology and Biometry Program at NHLBI, are available for comment on the study. To contact O'Leary, call the NEMC Press Office at (617) 636-0200; to contact Manolio, call the NHLBI Communications Office at (301) 496-4236. NHLBI press releases are available online at http://www.nhlbi.nih.gov/ Title: Ultrasonography Predicts Heart Attack/Stroke Risk From: The January 7, 1999 issue of The New England Journal of Medicine