What Causes Angina?
The most common cause of angina is coronary heart disease, which is the build-up of fatty deposits inside the walls of the coronary arteries.
As these fatty deposits, known as plaques, continue to build up, they narrow the arteries and can reduce the flow of blood. These plaques may sufficiently reduce blood flow in the coronary arteries to cause angina or heart attack.
In addition to coronary heart disease, angina may occur with other conditions, such as coronary spasm, a thickened heart muscle, valvular heart disease or severe anemia.
Oxygen Supply and Demand
During rest, there is normally a balance between the amount of oxygen delivered to the heart muscle (oxygen supply) and the amount of oxygen the heart muscle needs to work properly (oxygen demand).
During exertion, the heart muscle does extra work and thus temporarily needs more oxygen. A healthy heart has no problem meeting this extra demand, since the normal coronary arteries are able to deliver enough oxygen-rich blood to the heart muscle.
In patients with coronary heart disease, however, the narrowed or blocked arteries are unable to deliver the extra oxygen needed during activity.
The imbalance between oxygen supply and demand leads to a temporary lack of oxygen, or ischemia, to the heart muscle. Angina is the body's way of sending a warning that ischemia is occurring.
What Is Coronary Spasm?
In some patients, ischemia may be caused by spasm, a temporary contraction of the artery's walls. During spasm, a segment of the artery becomes narrowed, thus reducing blood flow to the heart muscle. Spasm can occur in arteries with or without plaques.
When caused by spasm, angina symptoms may not be brought on by exertion–instead, they often occur at rest, even during sleep.