November 13, 1995
Media Contact: John Cramer
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Johns Hopkins scientists may have found the first inherited risk factor for the development of blood clots that cause heart attacks, especially in younger people. One in five Americans may have it.
The factor is an abnormality in the shape of a hook-like protein prong that blood-clotting platelets use to link up -- "like bending a slightly barbed wire into the shape of a fishhook," says Ethan Weiss, the study's lead author and a fourth year student at the Johns Hopkins University School Medicine. "Just as a deeply curved hook would snag a fish more easily, the abnormally shaped prong may make the platelets link up more easily," says Weiss.
The factor, which appears to promote clots that can block blood vessels that nourish the heart, can be detected in a simple blood test. This factor might eventually be added to smoking, high blood pressure, high blood cholesterol and other major risk factors for heart disease, the nation's leading killer, according to investigators.
Weiss and his co-workers found the factor by comparing platelets of 71 people who had heart attacks with platelets of 68 patients who did not have heart attacks. Forty percent of the heart-attack patients -- and 50 percent of those under age 60 -- had the abnormality, while only 20 percent of the other patient group had the abnormality. Among the heart-attack patients, those with the abnormality had heart attacks on average seven years earlier than those without it.
"The results show there is a strong association between this genetic factor and heart attacks, particularly in young individuals," says Pascal Goldschmidt-Clermont, M.D., a senior author in the study and an associate professor of cardiology. "It could be the first inherited blood-clotting risk factor identified in coronary artery disease."
"Our next step is to find out what causes this genetic factor, so we can find a way around it," says Weiss.
Previous studies have shown that the absence of platelets' prongs weakens clotting, but this is the first evidence that a change in the prongs' shape may promote clotting, says Weiss. Platelets' prongs do not link up directly; they attach to a substance called fibrinogen that acts as a bridge between the platelets.
In other Hopkins studies:
Scientists found that African-Americans may have heart attacks earlier than whites because cholesterol build-up affects more of the heart's blood vessels in African-Americans. The finding may help persuade high-risk patients to adopt a "healthy-heart" lifestyle before a heart attack occurs, the scientists say. Previous studies by other investigators have found that in people having heart attacks, coronary arteries are not as severely narrowed by fatty material in African-Americans as in whites. Hopkins scientists studied 101 people with no symptoms of heart disease but who were at high risk for heart attacks because of family history. The results showed that the number of arteries narrowed by fatty material and the severity of the narrowing was the same in the two racial groups. But the fatty material covered twice the surface area of the coronary arteries in African-Americans as in whites, says Thomas Aversano, M.D., the study's lead author and an associate professor of medicine. "This greater burden, this greater length of artery covered by cholesterol build-up, could explain why African-Americans may be at higher risk for heart attacks at a young age," says Aversano. Smoking, diabetes, high blood pressure and cholesterol level were the same in the two racial groups.
Researchers found that an ultrasound-wave test can accurately predict which stroke patients are at high risk for heart attacks. In a study of 40 stroke patients with no previous record of heart disease, the ultrasound-wave test identified 24 patients as being at high risk for heart attacks caused by blood clots coming from the heart, says Joao Lima, M.D., the study's senior author and an assistant professor of medicine. The technique, called transesophageal echocardiography, uses echo images of the heart made from sound waves bounced through the esophagus, the muscular tube between the throat and stomach. The results led to changes in the treatment of 33 percent of the high-risk group.
Investigators found that people with low levels of a cholesterol-fighting particle may be at increased risk for coronary artery disease. The finding may be useful as a screening tool to identify high-risk patients before a heart attack occurs. Scientists studied blood-clotting cells called platelets and high- and low-density lipoproteins (fats carried in the blood bound to a "carrier" protein) in 196 people with no symptoms of heart disease. Results showed an increased risk for blood clots that can block arteries among patients with a low level of high-density lipoproteins (which carry cholesterol back to the liver to be excreted) and a low level of one of its "carrier" proteins. These low levels may also trigger an inherited tendency to develop blood clots that can block arteries narrowed by fatty materials, says James Roberts, M.D., the study's lead author and a cardiology fellow. Women who smoke may be at the most risk, the results suggested.
Scientists found that women who undergo coronary artery bypass surgery may further reduce their risk of heart attacks through follow-up nursing care to persuade them to stop smoking, lower their blood cholesterol level and exercise regularly. The lead author is Jerilyn K. Allen, Sc.D.