Heart disease's new measuring stick.

• Position: Cholesterol

In our increasingly health-conscious society, high cholesterol levels are so synonymous with heart disease that it no longer is open for question. Yet, perhaps it should be, suggests Robert S. Rosenson, professor of medicine and director of Lipoprotein Disorders and Clinical Atherosclerosis at the University of Michigan, Ann Arbor. He points out that recent studies indicate that cholesterol levels alone may not reflect an individual's cardiovascular disease risk accurately. According to the American Diabetes Association (ADA), Alexandria, Va., and the American College of Cardiology (ACC), Washington, D.C., sudden death is the first sign of heart disease in up to 30% of patients. Indeed, more than 50% of those who experience a heart attack have normal cholesterol levels, Rosenson indicates, adding that heart disease is caused by a complex series of events in which cholesterol plays a part, although perhaps not the starring role, as previously was thought.

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LDL, the so-called "bad" cholesterol, usually is characterized as a soft, waxy substance that travels freely in the blood; if there is too muCh, it can build up on artery walls and cause heart disease. Actually, just as oil does not mix with water, cholesterol does not travel freely in the bloodstream. Instead, it is carried in containers called low density lipoprotein particles (LDL-P). The interaction of these particles with the blood vessel wall can initiate a cascade of events that could lead to atherosclerosis or hardening of the arteries. LDL particles travel into the artery wall where they break open, deposit their cholesterol, and form plaques. Over time, the build-up of plaque can block the flow of blood, or can break off and cause a heart attack or stroke. Knowing your LDL-P can help reduce the risk of heart disease. The fewer particles there are, the less likely the onset.

A more simple way to think of the role that cholesterol and LDL-P play in heart disease is to compare them to a traffic jam, Rosenson explains. In this analogy, think of LDL particles as the cars on the highway, and cholesterol as the passengers in those cars. A traffic jam is caused by having too many cars on the road, not by having too many people in the cars. It is not the amount of cholesterol but the number of particles carrying it that can cause plaque build-up.

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