Atherosclerosis is the build-up of fatty material and other substances inside your arteries. It’s the underlying condition that causes most heart attacks and strokes.

The build-up occurs under the thin inside lining of the blood vessel and is called a plaque or atheroma. The plaque can harden the blood vessels and narrow the blood vessel to restrict blood flow.

The plaque can also break open which will trigger the formation of a blood clot. Such a blood clot can block the artery and completely stop blood flow. Atherosclerosis inside arteries happens gradually over decades. The more build-up there inside the arteries, the greater the risk of future heart disease or strokes. Atherosclerosis typically has no symptoms until it becomes very severe or causes a heart attack or stroke. Atherosclerosis can be largely prevented and improved by a healthy lifestyle.

Watch a visual explanation of atherosclerosis from the American Heart Association