The plaque that builds up in the arteries of people with coronary heart disease sometimes ruptures, causing a clot to form. If this clot blocks a coronary artery, it can cause a heart attack. Plaque in the carotid artery leading to the brain can rupture, breaking off and blocking a small blood vessel in the brain, causing a stroke. But what causes the plaque to rupture?

Researchers from Harvard Medical School recently announced their findings that plaques with more fat content are more likely to rupture than those containing calcium. Comparing the composition and structural integrity of arterial plaques, they found that fatty plaques were as much as 25% less stable than calcified plaques.

Such findings reinforce the value of lipid-lowering therapy in reducing heart attacks. It is now clearer why decreasing the extent of the lipid build-up can lower the internal stresses on the plaque and prevent it from tearing. This information also fits with the theories that the lipid-lowering drugs succeed in preventing heart attacks and strokes because they reduce the fat content of the plaques, making them more stable and therefore less likely to rupture.

Identifying factors that affect the structural stability of arterial plaque can help doctors identify which patients are most at risk and also to select the best treatment for them.

Sources:

• Huang H, Virmani R, Younis H, et al. Circulation, Feb. 27, 2001.
• AHA. Fatty plaque more likely to cause a heart attack than calcified plaque. AHA journal report, Feb. 26, 2001.