chest pain or chest discomfort produced when the heart muscle is not getting enough blood flow.
First, in contrast to stable angina, symptoms occur in a more random and unpredictable fashion. While in stable angina, symptoms typically are brought on by exertion, fatigue, anger, or some other form of stress, in unstable angina symptoms can occur without any apparent trigger. In fact, unstable angina often occurs at rest, and can even wake people from a restful sleep. Furthermore, in unstable angina, the symptoms often persist for more than just a few minutes, and nitroglycerin often fails to relieve the pain. So: unstable angina is "unstable" because symptoms may occur more frequently than usual, without any discernable trigger, and may persist for a long time.
it is most often caused by the actual rupture of a plaque in a coronary artery. In unstable angina, the ruptured plaque, and the blood clot that is almost always associated with the rupture, are producing partial blockage of the artery. The partial blockage may take a "stuttering" pattern (as the blood clot grows and shrinks), producing angina that comes and goes in an unpredictable fashion. If the clot should cause complete obstruction of the artery (which happens commonly), the heart muscle supplied by that affected artery is in grave danger of sustaining irreversible damage. In other words, the imminent risk of a complete myocardial infarction is very high in unstable angina.
If you have either unstable angina you will be treated with one of two general approaches: a) treat aggressively with drugs to stabilize the condition, then evaluate non-invasively, or b) treat aggressively with drugs to stabilize the condition, and schedule early invasive intervention (generally, angioplasty and stenting).