Angina pectoris is caused by a temporary inability of the coronary arteries to supply sufficient oxygenated blood to the heart muscle. The pain is felt in the chest and along the left arm. The pulse may become rapid and irregular. Angina pectoris commonly results from a disease of the wall of a coronary artery which causes it to narrow. This change in size of the artery prevents the blood from flowing freely to the heart muscle. The blood flow may also be affected when an artery is blocked by a blood clot. The disease usually appears after middle age and can appear suddenly. The pain may be precipitated by emotional strain, walking, running, or other physical exertion. The pain is a feeling of constriction rather than sharp or knifelike. The intensity varies from mild discomfort to severe. It frequently radiates to the left shoulder and then down the left arm to the elbow or wrist. The typical seizure lasts only a few minutes. Long periods of time may elapse between attacks during which time the person exhibits no negative symptoms and feels perfectly well. Some remedies that provide relief from the pain are nitroglycerin tablets or inhaling fumes of amyl nitrite. To prevent attacks, sufferers from the disease should also avoid physical and emotional strain, exercise, and whatever else has been known to cause an attack. Gradual weight reduction is strongly recommended in obese patients. The value of a low-fat diet is questionable, but moderation in dietary fat should be recommended for all patients. Smoking should be prohibited and alcoholic beverages are allowed in moderation. Average life expectancy is about 5 to 7 years from onset; however, the first attack may be fatal. Prognosis depends largely on the underlying disorder. False angina is a pain in the chest close to the heart, caused by nervousness, neuralgia, or rheumatism. It is not caused by disease of the heart. These pains do not move along the body, and are not a cause for alarm. False angina pains do not affect the circulation of the blood.