Plaque is a buildup of cholesterol, white blood cells, calcium, and other substances in the walls of arteries. Over time, plaque may narrow the artery.

Plaque sometimes reduces blood flow to the heart muscle, which can cause angina symptoms, such as chest pain or pressure. Plaque in the large artery in the neck (carotid artery stenosis) may reduce blood flow to the brain.

If a plaque breaks open or ruptures, the body will try to repair the injured artery lining. A blood clot may form and block blood flow. This blocked blood flow can cause a heart attack or stroke.