In most cases, unstable angina is caused by blood clots that partially or totally block a coronary artery. In someone at risk for unstable angina, blood clots can form for several reasons. The main cause is when plaque ruptures or breaks open (plaque is excess cholesterol and other debris that has built up inside a coronary artery). This can either narrow the artery even more than the plaque did or completely block it. Your body may be able to dissolve the clot, in which case, the symptoms of angina will improve. If the clot grows large enough to completely block the artery and the body cannot dissolve the clot, however, a heart attack will occur. Blood clots may form, partly dissolve, and later form again. Chest pain can occur each time a clot narrows or blocks an artery.
In a small number of people, symptoms of unstable angina can occur because of:
Chest pain or discomfort is the primary symptom of unstable angina. People with symptoms of an angina attack usually feel discomfort (often a pressure-like pain) in or around the chest, shoulders, jaw, neck, back, or arms. It may feel like a squeezing, pressing sensation in the chest.
Other symptoms of unstable angina can include:
- Indigestion or heartburn-type sensation
- Shortness of breath
Unlike stable angina, the pain or discomfort associated with unstable angina:
- Often occurs at rest, while sleeping at night, or with little physical exertion
- Is unexpected
- Is more severe and lasts longer (as long as 30 minutes) than episodes of stable angina
- Is usually not relieved with rest or angina medicine
- May get continuously worse
- May signal that a heart attack will happen soon.