Unstable Angina and Acute Coronary Syndrome. Unstable angina is a much more serious situation and is often an intermediate stage between stable angina and a heart attack, in which an artery leading to the heart (a coronary artery) becomes completely blocked. A patient is usually diagnosed with unstable angina under one or more of the following conditions:
- Pain awakens a patient or occurs during rest.
- A patient who has never experienced angina has severe or moderate pain during mild exertion (walking two level blocks or climbing one flight of stairs).
- Stable angina has progressed in severity and frequency within a 2-month period, and medications are less effective in relieving its pain.
Unstable angina is now usually discussed as part of a condition called acute coronary syndrome (ACS). ACS also includes people with a condition called NSTEMI (non ST-segment elevation myocardial infarction) -- also referred to as non-Q wave heart attack. With NSTEMI, the blood tests suggest a developing heart attack. These conditions are less severe than heart attacks but may develop into full-blown attacks without aggressive treatment. [For additional information on this syndrome see In-Depth Report #12: Heart attack and acute coronary syndrome.]
Prinzmetal's Angina. A third type of angina, called variant or Prinzmetal's angina, is caused by a spasm of a coronary artery. It almost always occurs when the patient is at rest. About two-thirds of people with it have severe atherosclerosis in at least one major blood vessel. Irregular heartbeats are common, but the pain is generally relieved immediately with standard treatment.
 | Click the icon to see an image of a coronary artery spasm. |
Silent Ischemia. Some people with severe coronary artery disease do not experience angina pain. This condition is known as silent ischemia, which some experts attribute to abnormal processing of heart pain by the brain. This is a dangerous condition because patients have no warning signs of heart disease. Some studies suggest that people with silent ischemia experience higher complication and mortality rates than those with angina pain. (Angina pain may actually protect the heart by conditioning it before a heart attack.)
Syndrome X. Syndrome X is a condition that occurs when patients have atypical angina chest pain. Their electrocardiograms are abnormal during a stress test, but they have no signs of blocked arteries. It is more likely to occur in women. Although it unclear what causes this condition, imaging tests suggest that Syndrome X may also be caused by ischemia, as is angina.
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