Angina pectoris (or just angina) is a condition marked by recurring pain or discomfort in the chest caused by a sudden decrease of blood supply to the heart. It apparently feels like a pressing or squeezing pain in the chest under the breast bone, sometimes in the shoulders, arms, neck, jaws, or back. It's usually brought on by exercise, and occurs because the heart needs more oxygen than the blood nourishing it can supply. Stress, extreme cold or heat, heavy meals, alcohol and cigarette smoking can also trigger episodes of angina. Angina is a symptom of coronary artery disease or heart disease, which is caused by atherosclerosis or blockage of the blood vessels. Angina can be diagnosed by taking a patient history, though the doctor may use other diagnostic tools to confirm the diagnosis, including electrocardiogram (ECG or EKG), stress test, and/or x-ray of the coronary arteries to determine the level of vessel blockage.
Although it must feel like you're about to have a heart attack when you have an episode of angina, angina is not a heart attack. A heart attack occurs when the blood flow to part of the heart is suddenly, and permanently, cut off; it causes permanent and irreversible damage to the heart muscle. Heart attacks are typically accompanied by more severe pain than angina; the pain lasts longer and is not eased by rest or medicine. Increase in the severity of angina, though, may mean that a heart attack is imminent.
Treating angina ideally involves treating the causes of the underlying coronary artery disease: lowering blood pressure, quitting smoking, lowering cholesterol levels, losing weight. These should lessen the incidence of angina and reduce the likelihood that the condition will lead to a heart attack. Angina may also be treated with nitroglycerine, which widens the blood vessels, or beta blockers, which slow the heart rate. In severe cases, when heart attack seems imminent and lifestyle change unreachable, more aggressive treatments surgery or angioplasty may be required.
Some useful online resources which I used in writing this node can be found at
http://www.nhlbi.nih.gov/health/public/heart/other/angina.htm
http://www.medinfo.co.uk/conditions/angina.html
http://familydoctor.org/handouts/233.html