Unstable angina is a condition more serious than stable angina and less serious than an actual heart attack. Stable angina is chest pain from a temporary decrease in oxygen to the heart that is caused by exertion and goes away with rest. A heart attack is a prolonged decrease in oxygen to the heart that results in permanent damage to the heart.

What is going on in the body?

Atherosclerosis, or hardening of the arteries, is a condition in which fatty deposits, or plaque, form inside blood vessel walls. Atherosclerosis that involves the arteries supplying the heart is known as coronary artery disease. Plaque can block the flow of blood through the arteries. The tissues that normally receive blood from these arteries then begin to suffer damage from a lack of oxygen. When the heart does not have enough oxygen, it responds by causing the pain and discomfort known as angina.

Unstable angina occurs when the narrowing becomes so severe that not enough blood gets through to keep the heart functioning normally, even at rest. Sometimes the artery can become almost completely blocked. With unstable angina, the lack of oxygen to the heart almost kills the heart tissue.

What are the causes and risks of the condition?

The factors that increase the risk of unstable angina include: