Reduction of Blood Flow to Heart Muscle
Angina is a symptom of coronary artery disease (CAD) and is caused by reduced blood flow to your heart muscle.
Narrowing of the Arteries (Atherosclerosis)
The narrowing of the arteries in CAD is caused by a process called
atherosclerosis. People with atherosclerosis have a build-up of a substance called plaque inside the wall of their arteries.
Plaque is made up of fat, cholesterol, calcium deposits, and white blood cells that have gotten into the artery wall. The plaque causes the wall to "bulge" into the inside of the artery where the blood normally flows. The bulge can partly or completely restrict the flow of blood in a particular artery.
Lack of Oxygen (Ischemia)
When blood flow is restricted, the heart muscle does not get the oxygen that it needs to function properly. Angina is the symptom of this lack of oxygen, called
Stable angina occurs when you
increase the heart's work load as a result of exercise. A blockage of CAD limits the extra flow required by the extra work load causing angina. When exercise is discontinued, the anginal pain resolves.
Unstable angina is caused when narrowed arteries are
further blocked by a ruptured plaque and blood clot. This is a warning sign for complete blockage or heart attack.
Variant angina, which is rare, is caused by a spasm, or contraction, in a coronary artery, causing it to
narrow temporarily. It is not related to atherosclerosis.