Heart Disease: An Introduction to Coronary Artery Disease

Click the icon to see an image of cholesterol inside an artery.

Oxidation. The damaging process called oxidation is an important trigger in the atherosclerosis story.

• Oxidation is a chemical process in the body caused by the release of unstable particles known as oxygen-free radicals. It is one of the normal processes in the body, but under certain conditions (such as exposure to cigarette smoke or other environment stresses) these free radicals are overproduced.
• In excess amounts, they can be very dangerous, causing damaging inflammation and even affecting genetic material in cells.
• In heart disease, free radicals are released in artery linings and oxidize low-density lipoproteins (LDL). The oxidized LDL is the basis for cholesterol build-up on the artery walls and damage leading to heart disease.

Inflammatory Response. For the arteries to harden there must be a persistent reaction in the body that causes ongoing harm. Researchers now believe that this reaction is an immune process known as the inflammatory response. The following is one theory about how the inflammatory response contributes to heart disease:

• The injuries to the arteries during oxidation signal the immune system to release white blood cells (particularly those called neutrophils and macrophages) at the site. These factors initiate the inflammatory response.
• Macrophages literally "eat" foreign debris, in this case oxidized LDL cholesterol.
• The process converts LDL cholesterol into foamy material that attaches to the smooth muscle cells of the arteries. The cholesterol becomes mushy and accumulates on artery walls.
• Over time the cholesterol dries and forms a hard plaque, which causes further injury to the walls of the arteries.
• In response to this additional harm, the immune system releases other factors called cytokines. These are powerful inflammatory molecules that attract more white blood cells and perpetuate the whole cycle, causing persistent injury to the arteries.

Click the icon to see an image of atherosclerosis.