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Heart Disease Health Center

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Atherosclerosis: What’s Happening Inside Your Arteries?

Could atherosclerosis already be clogging your arteries?

Atherosclerosis: "Stable" and "Unstable" Plaques continued...

Rather, the plaques to watch out for are the young punks down the block. "Most heart attacks occur because of sudden changes in plaques that only block 20% or 30% of an artery," says Jeff Borer, MD, professor of cardiovascular medicine at Weill Cornell Medical College in New York.

These small but deadly plaques are hard to detect, even with advanced tests for atherosclerosis. "Generally, we just have to infer they're there from the presence of bigger blockages elsewhere," says Borer.

Learning why these smaller plaques rupture is a key focus of ongoing research. Studies over the past decade have demonstrated that inflammation inside the plaque is the key

Atherosclerosis: Inflammation in Your Arteries

How does a plaque become inflamed? As plaques grow, leukocytes and muscle cells gather inside. The leukocytes attempt to digest the LDL cholesterol.

That may sound like a good thing. But leukocytes' job description includes releasing chemicals that can be destructive. The local muscle cells also release damaging substances.

The result can be a dissolving of the interior of a stable plaque, rendering it unstable. If the cap of the plaque breaks off, dangerous materials inside are exposed to blood flowing by. A blood clot forms rapidly in the artery, causing a heart attack or stroke.

Severe but stable blockages can often be seen on a stress test or coronary angiogram. However, smaller, dangerous plaques usually go undetected. And with current knowledge, "it's impossible to determine when these plaques are inflamed and therefore more likely to rupture," explains Borer.

Using a marker in the blood called C-reactive protein (CRP), doctors can get a general idea of the level of inflammation in the body. This test can't predict heart attacks or strokes with accuracy, though.

Atherosclerosis: Calcium and Hardening of the Arteries

Why is atherosclerosis often described as "hardening of the arteries?" As plaques grow and evolve in the artery walls, calcium deposits inside them. The calcium makes the plaque firm and the artery stiffer. In general, stable plaques contain more calcium.

A relatively new test called electron-beam computed tomography (EBCT) can calculate the amount of calcium in the coronary arteries and help predict the risk of heart attack in certain people.

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