Coronary artery disease occurs when the major blood vessels that supply the heart with oxygen and nutrients become damaged.
CAD affects more than 1.6million men and one million women in the UK, and a total of 15million adults in the US.
It is usually due to plaque and inflammation.
When plaque builds up, it narrows the arteries, which decreases blood flow to the heart.
Over time this can cause angina, while a complete blockage can result in a heart attack.
Many people have no symptoms at first but as the plaque builds up they may notice chest pains or shortness of breath when exercising or stressed.
Other causes of CAD include smoking, diabetes and an inactive lifestyle.
It can be prevented by quitting smoking, controlling conditions like diabetes or high blood pressure, staying active, eating well and managing stress.
Drugs can help to lower cholesterol, while aspirin thins the blood to reduce the risk of clots.
In severe cases, stents can be put into the arteries to open them, while coronary bypass surgery creates a graft to bypass the blocked arteries using a vessel from another part of the body.
-Daily Mail.uk