What Causes Angina?

Underlying Causes

Angina is a symptom of an underlying heart condition. Angina pain is the result of reduced blood flow to an area of heart muscle. Coronary artery disease (CAD) usually causes the reduced blood flow.

This means that the underlying causes of angina are generally the same as the underlying causes of CAD.

Research suggests that damage to the inner layers of the coronary arteries causes CAD. Smoking, high levels of fat and cholesterol in the blood, high blood pressure, and a high level of sugar in the blood (due to insulin resistance or diabetes) can damage the coronary arteries.

When damage occurs, your body starts a healing process. Excess fatty tissues release compounds that promote this process. This healing causes plaque to build up where the arteries are damaged. Plaque narrows or blocks the arteries, reducing blood flow to the heart muscle.

Some plaque is hard and stable and leads to narrowed and hardened arteries. Other plaque is soft and is more likely to break open and cause blood clots.

The buildup of plaque on the arteries' inner walls can cause angina in two ways. It can:

• Narrow the arteries and greatly reduce blood flow to the heart
• Form blood clots that partially or totally block the arteries

Immediate Causes

There are different triggers for angina pain, depending on the type of angina you have.

Stable Angina

Physical exertion is the most common trigger of stable angina. Severely narrowed arteries may allow enough blood to reach the heart when the demand for oxygen is low (such as when you're sitting). But with exertion, like walking up a hill or climbing stairs, the heart works harder and needs more oxygen.

Other triggers of stable angina include:

• Emotional stress
• Exposure to very hot or cold temperatures
• Heavy meals
• Smoking

Unstable Angina

Blood clots that partially or totally block an artery cause unstable angina. If plaque in an artery ruptures or breaks open, blood clots may form. This creates a larger blockage. A clot may grow large enough to completely block the artery and cause a heart attack. For more information, see the animation in "What Causes a Heart Attack?"

Blood clots may form, partly dissolve, and later form again. Angina can occur each time a clot blocks an artery.

Variant Angina

A spasm in a coronary artery causes variant angina. The spasm causes the walls of the artery to tighten and narrow. Blood flow to the heart slows or stops. Variant angina may occur in people with or without CAD.

Other causes of spasms in the coronary arteries are:

• Exposure to cold
• Emotional stress
• Medicines that tighten or narrow blood vessels
• Smoking
• Cocaine use