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Heart attacks and what causes them...click here

Angina and Coronary Artery Disease

WHAT IS CORONARY ARTERY DISEASE? The heart is the human body's hardest-working organ.  Throughout life it continuously pumps blood enriched with oxygen and vital nutrients through a network of arteries to all parts of the body's tissues.       The external structures of the heart include the ventricles, atria, arteries and veins. Arteries carry blood away from the heart while veins carry blood into the heart. The vessels colored blue indicate the transport of blood with relatively low content of oxygen and high content of carbon dioxide. The vessels colored red indicate the transport of blood with relatively high content of oxygen and low content of carbon dioxide. In order to perform the arduous task of pumping blood to the rest of the body, the heart muscle itself needs a plentiful supply of oxygen-rich blood, which is provided through a network of coronary arteries. These arteries carry oxygen-rich blood to the heart?s muscular walls (the myocardium). Click the icon to see an image of the anterior heart arteries. If blood flow to the myocardium is interrupted, an injury known as an infarct occurs, or in other words, a myocardial infarction, more commonly known as a heart attack. Click the icon to see an animation about coronary artery disease. The Process of Atherosclerosis Coronary artery disease is the end result of a complex process called atherosclerosis (commonly called "hardening of the arteries"). This causes blockage of arteries (ischemia) and prevents oxygen-rich blood from reaching the heart. There are many steps in the process leading to atherosclerosis and some are not fully understood. Click the icon to see an image of atherosclerosis. Increasingly, however, researchers are studying the interactions between cholesterol and processes known as oxidation and the inflammatory response: Cholesterol and Lipoproteins. The story begins with cholesterol and sphere-shaped bodies called lipoproteins that transport cholesterol. Cholesterol is a white, powdery nutrient that is found in all animal cells and in animal-based foods. It is critical for many functions, but under certain conditions cholesterol can have harmful effects. The lipoproteins that transport cholesterol are referred to by their size. The most commonly known are low-density lipoproteins (LDL) and high-density lipoproteins (HDL). LDL is often referred to as the "bad" cholesterol and HDL as the "good" cholesterol. Click the icon to see an image of cholesterol inside an artery. Oxidation. The damaging process called oxidation is an important trigger in the atherosclerosis story. Oxidation is a chemical process in the body caused by the release of unstable particles known as oxygen free radicals. It is one of the normal processes in the body, but under certain conditions (such as exposure to cigarette smoke or other environment stresses) these free radicals are over-produced. In excess amounts, they can be very dangerous, including damaging cells and even effecting genetic material. In heart disease, free radicals are released in artery linings and oxidize low-density lipoproteins (LDL). The oxidized LDL is the basis for cholesterol buildup on the artery walls. Inflammatory Response. For the arteries to harden there must be a persistent reaction in the body that causes ongoing harm. Researchers now believe that this reaction is an immune process known as the inflammatory response. The following is one theory about how the inflammatory response contributes to heart disease: The injuries to the arteries during oxidation signal the immune system to release white blood cells (particularly those called neutrophils and macrophages) at the site. These factors initiate the inflammatory response. Macrophages consume foreign debris, in this case oxidized LDL cholesterol. The process converts LDL cholesterol into foamy cells that attach to the smooth muscle cells of the arteries. The cholesterol becomes mushy and accumulates on artery walls. Over time the cholesterol dries and forms a hard plaque, which causes further injury to the walls of the arteries. In response to this additional harm, the immune system releases other factors called cytokines. These are powerful inflammatory molecules that attract more white blood cells and perpetuate the whole cycle, causing persistent injury to the arteries. Click the icon to see an image of atherosclerosis. Evidence is growing that the inflammatory response may be present not just in local plaques in single arteries but that it occurs throughout the arteries leading to the heart. Blockage in the Arteries. Eventually these calcified (hardened) arteries become narrower (a condition known as stenosis). As this narrowing and hardening process continues, blood flow slows and prevents sufficient oxygen-rich blood from reaching the heart. Such oxygen deprivation in vital cells is called ischemia. When it affects the coronary arteries, it causes injury to the tissues of the heart. Injured inner vessel walls also fail to produce enough nitric oxide, a substance critical for maintaining blood vessel elasticity. These narrow and inelastic arteries not only slow down blood flow but also become vulnerable to injury and tears. Click the icon to see an image of coronary artery blockage The End Result: Heart Attack. Heart attack can occur as a result of one or two effects of atherosclerosis: If the artery becomes completely blocked and ischemia becomes so extensive that oxygen-bearing tissues around the heart die. If the plaque itself develops fissures or tears. Blood platelets adhere to the site to seal off the plaque and a blood clot (thrombus) forms. A heart attack can then occur if the formed blood clot completely blocks the passage of oxygen-rich blood to the heart. Click the icon to see an image of the developmental process of atherosclerosis. Angina Angina is the primary symptom of coronary artery disease and, in severe cases, of a heart attack. It is typically experienced as chest pain and occurs when the heart muscle doesn't get as much blood (hence as much oxygen) as it needs for a given level of work (ischemia). Click the icon to see an image about angina. Angina is usually referred to as stable (predictable) or unstable (less predictable and a sign of a more serious situation). Angina itself is not a disease. Much evidence exists, in fact, that onset of angina less than 48 hours before a heart attack may be protective, possibly by conditioning the heart to resist the damage resulting from the attack. Click the icon to see an image of angina. Angina may be experienced in different ways and can be mild, moderate, or severe. Some common indications of angina are as follows: It is often reported as a dull, heavy pressure that may resemble a crushing object on the chest. Pain often radiates to the neck, jaw, or left shoulder and arm. Less commonly, patients report mild burning chest discomfort, sharp chest pain, or pain that radiates to the right arm or back. Sometimes a patient experiences shortness of breath, fatigue, or palpitations instead of pain. The intensity of the pain does not always relate to the severity of the medical problem. Some people may feel a crushing pain from mild ischemia, while others might experience only mild discomfort from severe ischemia. Some people have also reported a higher sensitivity to heat on the skin with the onset of angina. Stable Angina. Stable angina is predictable chest pain. Although less serious than unstable angina, it can be extremely painful. It is usually relieved by rest and responds well to medical treatment (typically nitroglycerin). Any event that increases oxygen demand can cause an angina attack. Some typical triggers include the following: Exercise. Cold weather. Emotional tension. Large meals. Angina attacks can occur at any time during the day, but a high proportion seems to take place between the hours of 6:00 AM and noon. Unstable Angina. 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 two-month period, and medications are less effective in relieving its pain. It should be noted that unstable angina is now usually discussed to as of a condition called acute coronary syndrome. This condition also includes non Q-wave myocardial infarction, which is diagnosed when blood tests and ECGs suggest a developing heart attack. In such cases, injury in the arteries appears to be less severe than with a full-blown heart attack. [For additional information on this syndrome see 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 Prinzmetal's angina 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, a condition 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. In one study, people with silent ischemia experienced much higher complication and mortality rates than those with anginal 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, sensitive imaging tests are suggesting that syndrome X may also be caused by ischemia, as is angina.