Causes

The leading cause of angina is atherosclerosis (or arteriosclerosis). In order to perform the arduous task of pumping blood, the heart muscle needs a plentiful supply of oxygen-rich blood, which is provided through a network of coronary arteries. Coronary artery disease is the end result of atherosclerosis (commonly called "hardening of the arteries"), a process in which arteries narrow, preventing sufficient oxygen-rich blood from reaching the heart. Oxygen deprivation in vital cells (called ischemia) causes injury to the tissues of the heart. If the artery becomes completely blocked, damage becomes so extensive that cell death, a heart attack, occurs.

Atherosclerosis is triggered by excess amounts of unstable particles known as oxygen - free radicals, which bind with and alter other molecules, a process called oxidation. The particles are released as part of normal bodily processes, but environmental toxins, such as viruses or smoking, can produce excess amounts. When free radicals are released in artery linings, they react with and oxidize low-density lipoproteins (LDL, the so-called bad cholesterol). LDL then deposits mushy layers of oxidized cholesterol on the walls of the artery. The cholesterol accumulates and eventually hardens into plaques.

But that isn't the end of the story. The injuries to the arteries signal the immune system to release white blood cells (particularly those called neutrophils and macrophages) at the site; this initiates a process called the inflammatory response. Macrophages literally "eat" foreign debris, in this case oxidized cholesterol, and become foamy cells that attach to smooth muscle cells causing them to build up. The immune system, sensing further harm, releases other factors called cytokines, which attract more white blood cells and perpetuate the whole cycle. They also stimulate the liver to produce blood-clotting factors called fibrinogen and C-reactive protein. Injured inner walls fail to produce enough nitric oxide, a substance critical for maintaining blood vessel elasticity. The arteries become calcified and lose elasticity. As this process continues, blood flow slows. A heart attack usually occurs when a blood clot forms completely sealing off the passage of blood. This typically happens when the plaque itself develops fissures or tears; blood platelets adhere to the site to seal off the plaque and a blood clot (thrombus) forms.

Atherosclerosis affects many people in developed countries. It may start as early as in the twenties and increases with age. Numerous 'risk factors' are known to be associated with the development of arteriosclerosis:

• a family history of atherosclerosis
• hypercholesterolaemia-a high content of (LDL) cholesterol in the blood
• hypertension(high blood pressure)
• smoking
• being male
• diabetes type 1 and type 2
• obesity
• stress
• lack of regular exercise

Although atherosclerosis is far and away the leading cause of angina, other conditions can impair the delivery of oxygen to the heart muscle and cause pain. Such conditions include: spasm in the coronary artery, abnormalities of the heart muscle itself, hyperthyroidism, anaemia, vasculitis (a group of disorders that cause inflammation of the blood vessels), and, in rare cases, exposure to high altitudes. Many conditions may cause chest pains unrelated to heart or blood vessel abnormalities. High on the list are anxiety attacks, gastrointestinal disorders (gallstone attacks, peptic ulcer disease, hiatal hernia, heartburn), lung disorders (asthma, blood clots, bronchitis, pneumonia, collapsed lung), and problems affecting the ribs and chest muscles (injured muscles, fractures, arthritis, spasms, infections).