Any event that increases oxygen demand can cause angina, including exercise, cold weather, emotional tension, and even large meals. Unstable angina is a much more serious situation and is often an intermediate stage between stable angina and a heart attack. Medications are less effective in relieving pain of unstable 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.
Irregular heartbeats are common, but the pain is generally relieved immediately with treatment.
Some people with severe coronary artery disease do not experience angina pain, a condition known as silent ischemia, which some experts attribute to abnormal processing of heart pain by the brain. Coronary artery disease is the leading killer in America of both men and women, responsible for over 475,000 deaths in 1996. On the positive side, mortality rates from coronary artery disease have significantly declined in industrialized countries over the past few decades, although they are on the rise in developing nations. When the necessary lifestyle changes are enacted in combination with appropriate medical or surgical treatments, a person suffering angina and heart disease has a good chance of living a normal life. Much evidence exists, in fact, that onset of angina less than 48 hours before a heart attack is actually protective, possibly by conditioning the heart to resist the damage resulting from the attack.