Coronary artery disease (CAD) occurs when the arteries that supply blood to the heart muscle (the coronary arteries) become hardened and narrowed. The arteries harden and narrow due to build-up of fatty deposits called plaque on their inner walls. The hardening of the artery walls is known as arteriosclerosis, while the build-up of plaque is known as atherosclerosis. As the plaque increases in size, the insides of the coronary arteries get narrower and less blood can flow through them. Eventually, blood flow to the heart muscle is reduced and can cause chest pain (angina). A sudden, complete blockage can lead to a heart attack.

Many people with this disease are not aware they have it, as it develops slowly and silently over decades. It can go virtually unnoticed until it produces a heart attack.