You've surely heard a lot about the risks of high levels of LDL (low-density lipoprotein) cholesterol and low levels of HDL (high-density lipoprotein) cholesterol in the blood. But you probably haven't heard about lipoprotein (a)-abbreviated Lp(a) - another lipoprotein that contributes to the development of atherosclerotic plaques.

Lp(a) contributes to atherosclerosis in two ways. Like LDL, Lp(a) can deposit its cholesterol in the coronary arteries and in other arteries throughout the body. In addition, because apo(a)-a constituent of Lp(a)-has a similar structure to the clot-busting blood protein plasminogen, elevated Lp(a) levels may disrupt the normal removal of a clot that could block an artery.

Elevated blood levels of Lp(a) are considered a minor risk factor compared with LDL cholesterol or cigarette smoking, for example. Nonetheless, high Lp(a) does contribute to the risk of coronary heart disease. In fact, I have seen two members of our faculty at Johns Hopkins who required coronary artery bypass surgery at a relatively young age, even though a high Lp(a) was their only risk factor.

There are no known strategies for successfully lowering Lp(a). Treatment with the drug niacin has been reported to lower Lp(a), but that did not work in the two patients mentioned above. Their experience made me stop trying to lower Lp(a) levels. Instead, I have considered a high Lp(a) as another reason to lower LDL cholesterol as aggressively as possible.