What Causes Coronary Artery Disease?

Coronary artery disease (CAD) is caused by atherosclerosis (the thickening and hardening of the inside walls of arteries). Some hardening of the arteries occurs normally as a person grows older.

In atherosclerosis, plaque deposits build up in the arteries. Plaque is made up of fat, cholesterol, calcium, and other substances from the blood. Plaque buildup in the arteries often begins in childhood. Over time, plaque buildup in the coronary arteries can:

• Narrow the arteries. This reduces the amount of blood and oxygen that reaches the heart muscle.
• Completely block the arteries. This stops the flow of blood to the heart muscle.
• Cause blood clots to form. This can block the arteries that supply blood to the heart muscle.

The illustration shows a normal artery with normal blood flow (Figure A) and an artery containing plaque buildup (Figure B).

Plaque in the arteries can be:

• Hard and stable. Hard plaque causes the artery walls to thicken and harden. This condition is associated more with angina than with a heart attack, but heart attacks frequently occur with hard plaque.
• Soft and unstable. Soft plaque is more likely to break open or to break off from the artery walls and cause blood clots. This can lead to a heart attack.