Definition of Unstable angina:

Unstable angina is a type of acute chest pain that occurs when your heart doesn't get enough oxygen. It can be a warning sign of a heart attack.

See also:

• Stable angina
• Variant angina

Causes, incidence, and risk factors:

Coronary artery disease due to atherosclerosis is by far the most common cause of unstable angina. Atherosclerosis is the build up of fatty material called plaque along the walls of the arteries. This causes arteries to become less flexible and narrow, which interrupts blood flow to the heart, causing chest pain.

At first, angina may be considered stable -- that is, the chest pain only occurs with activity or stress. Unstable angina is chest pain that is sudden and gets increasingly worse. The chest pain:

• Occurs without cause (for example, it wakes you up from sleep)
• Lasts longer than 15 - 20 minutes
• Responds poorly to a medicine called nitroglycerine
• May occur along with a drop in blood pressure or significant shortness of breath

A coronary artery spasm is a rare cause of angina.

Risk factors for unstable angina are similar to those for stable angina and coronary artery disease. They include:

• Being male
• Diabetes
• Getting older
• Family history of coronary heart disease before age 50
• High blood pressure
• High LDL cholesterol
• Low HDL cholesterol
• Not getting enough exercise
• Smoking
• Obesity