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infarction

 
Medical Encyclopedia: Heart Attack

Definition

A heart attack is the death of, or damage to, part of the heart muscle because the supply of blood to the heart muscle is severely reduced or stopped.

Description

Heart attack is the leading cause of death in the United States. More than 1.5 million Americans suffer a heart attack every year, and almost half a million die, according to the American Heart Association. Most heart attacks are the end result of years of silent but progressive coronary artery disease, which can be prevented in many people. A heart attack is often the first symptom of coronary artery disease. According to the American Heart Association, 63% of women and 48% of men who died suddenly of coronary artery disease had no previous symptoms. Heart attacks are also called myocardial infarctions (MIs).

A heart attack occurs when one or more of the coronary arteries that supply blood to the heart are completely blocked and blood to the heart muscle is cut off. The blockage is usually caused by atherosclerosis, the buildup of plaque in the artery walls, and/or by a blood clot in a coronary artery. Sometimes, a healthy or atherosclerotic coronary artery has a spasm and the blood flow to part of the heart decreases or stops. Why this happens is unclear, but it can result in a heart attack.

About half of all heart attack victims wait at least two hours before seeking help. This increases their chance of sudden death or being disabled. The longer the artery remains blocked during a heart attack, the more damage will be done to the heart. If the blood supply is cut off severely or for a long time, muscle cells suffer irreversible injury and die. The patient can die. That is why it is important to recognize the signs of a heart attack and seek prompt medical attention at the nearest hospital with 24-hour emergency cardiac care.

About one fifth of all heart attacks are silent, that is, the victim does not know one has occurred. Although the victim feels no pain, silent heart attacks can still damage the heart.

The outcome of a heart attack also depends on where the blockage is, whether the heart rhythm is disturbed, and whether another coronary artery supplies blood to that part of the heart. Blockages in the left coronary artery are usually more serious than in the right coronary artery. Blockages that cause an arrhythmia, an irregular heartbeat, can cause sudden death.

— Lori De Milto



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Dictionary: in·farc·tion   (ĭn-färk'shən) pronunciation
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n.
  1. The formation or development of an infarct.
  2. An infarct.

Sci-Tech Encyclopedia: Infarction
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The process of anoxic tissue death. The usual cause is occlusion of an artery by a thrombus or embolus and sometimes by severe atherosclerosis. The development of the infarct depends to a great extent on the collateral circulation. If the collateral blood supply is inadequate or if the vessel is the sole source of blood supply to the region, an infarct results. See also Arteriosclerosis.

Infarcts commonly occur in the lungs, heart, brain (see illustration), spleen, and kidneys. The common cause of infarcts of the heart is thrombosis of the coronary artery, usually secondary to atherosclerosis. Hemorrhage into an atherosclerotic plaque can also result in thrombosis of an artery. Myocardial infarcts usually involve the left ventricle or interventricular septum and only rarely involve the right ventricle or atria. The location of the infarct usually depends on the coronary artery occluded. See also Heart disorders.

Gross photograph of a brain section, showing a wedge-shaped infarct that resulted from a thrombus. Secondary hemorrhage has occurred.
Gross photograph of a brain section, showing a wedge-shaped infarct that resulted from a thrombus. Secondary hemorrhage has occurred.

Infarction of a portion of bowel will result in death unless surgical intervention is forthcoming. Embolization to the lungs is a rather frequent occurrence. However, because of the collateral blood supply of the lungs, infarction follows only when there is some interference with the circulation, such as chronic pulmonary venous congestion. An extensive collateral circulation also exists in the liver, hence the rarity of infarcts in this organ. See also Circulation disorders.


Food and Nutrition: infarction
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Death of an area of tissue because its blood supply has been stopped.

 
Columbia Encyclopedia: infarction
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infarction, blockage of blood circulation to a localized area or organ of the body resulting in tissue death. Infarctions commonly occur in the spleen, kidney, lungs, brain, and heart. The acute emergency known as myocardial infarction or
heart attack
is usually caused by a blockage in one of the coronary arteries that supply blood to the heart muscle. The blockage typically occurs when a blood clot (see thrombosis) lodges in an area already narrowed by arteriosclerosis; other causes are vasospasms in the arterial walls or viral infection of the heart. Symptoms include a crushing pain in the chest radiated to either arm (more commonly the left arm), the jaw, and the neck. The pain may be experienced, particularly in women, as pain in the shoulder or stomach, instead of the chest, and in some cases there are no symptoms at all. The seriousness of the infarction is dependent upon the amount of heart muscle affected, how long the area is deprived of blood, and whether it affects the natural pacemaker of the heart, setting off arrhythmias such as ventricular fibrillation. Death of heart muscle tissue and heart failure may result (see congestive heart failure); damage to other vital organs, including the brain, may occur if the heart is unable to pump necessary oxygen and blood to them. Confirmation of myocardial infarction is made by electrocardiography and measurement of elevations of white blood cells and certain enzymes. Treatment of acute myocardial infarction may include first aid in the form of cardiopulmonary resuscitation (CPR), an emergency balloon angioplasty, or the administration of beta-blockers and thrombolytic drugs (clot-dissolving drugs), such as tissue plasminogen activator. The healing of an infarction occurs through replacement of the dead tissue by scar tissue.

See also coronary artery disease.


Veterinary Dictionary: infarction
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1. the formation of an infarct.
2. an infarct.

  • cardiac i. — see myocardial infarction (below) and also myocardial infarction.
  • cerebral i. — an ischemic condition of the brain, causing a persistent focal neurological deficit in the area affected.
  • i. fever — an aseptic fever caused by liberation of pyrogens from damaged tissue.
  • intestinal i. — a common occurrence in horses due to occlusion of arteries by larvae of Strongylus vulgaris. Sections of intestine, sometimes very large ones, become devitalized leading to peritonitis and death.
  • — May also result from torsion or strangulation. See also thromboembolic colic.
  • myocardial i. — gross necrosis of the myocardium, due to interruption of the blood supply to the area. See also myocardial infarction.
  • pulmonary i. — localized necrosis of lung tissue, due to obstruction of the arterial blood supply.
  • renal i. — is usually conical, anemic and multiple and may heal leaving a narrow scar. It is usually clinically inapparent unless the obstructing material is infected. This leads to the development of renal abscess or embolic nephritis, also usually without clinical signs unless the abscesses are large or numerous.
  • spinal cord i. — caused sometimes by fibrocartilaginous emboli of prolapsed disk material, causing sudden loss of function of large sections of the spinal cord, leading to flaccid paralysis of the hindlimbs or of all four, depending on the site of the infarct.
  • splenic i. — usually hemorrhagic; may be difficult to differentiate from subcapsular hematoma.
  • venous i. — a thrombus in a vein may cause infarction, e.g. in the thigh muscles of downer cow, recumbent for long periods, or in the gastric mucosa of pigs, where it is a common finding in acute septicemia.
Obscure Words: infarction
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medical  necrosis
Wikipedia: Infarction
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In medicine, an infarction is the process of tissue death (necrosis) caused by blockage of the tissue's blood supply. The supplying artery may be blocked by an obstruction (e.g. an embolus, thrombus, or atherosclerotic plaque), may be mechanically compressed (e.g. tumor, volvulus, or hernia), ruptured by trauma (e.g. atherosclerosis or vasculitides), or vasoconstricted (e.g. cocaine vasoconstriction leading to myocardial infarction).

Infarctions are commonly associated with hypertension or atherosclerosis. In atherosclerotic formations a plaque develops under a fibrous cap. When the fibrous cap is degraded by metalloproteinases released from macrophages or by intravascular shear force from blood flow subendothelial thrombogenic material (extracellular matrix) is exposed to circulating platelets and thrombus formation occurs on the vessel wall occluding blood flow. Occasionally, the plaque may rupture forming an embolus that travels with the blood flow downstream where the vessel narrows and eventually clogs the vessel lumen. Infarctions can also involve mechanical blockage of the blood supply, such as when part of the gut or testicles herniates or becomes involved in a volvulus.

Classification

Infarctions are divided into 2 types according to the amount of blood present:

Diseases

Diseases commonly associated with infarctions include:

References


 
 
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MI
MIMI
MI (abbreviation)

What are myocardial infarctions? Read answer...
What is a myocardial infarction? Read answer...
What is the Prognosis for myocardial infarction? Read answer...

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What is a nonacute infarction?
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What is an ischemic infarction?

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Sci-Tech Encyclopedia. McGraw-Hill Encyclopedia of Science and Technology. Copyright © 2005 by The McGraw-Hill Companies, Inc. All rights reserved.  Read more
Food and Nutrition. A Dictionary of Food and Nutrition. Copyright © 1995, 2003, 2005 by A. E. Bender and D. A. Bender. All rights reserved.  Read more
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Veterinary Dictionary. Saunders Comprehensive Veterinary Dictionary 3rd Edition. Copyright © 2007 by D.C. Blood, V.P. Studdert and C.C. Gay, Elsevier. All rights reserved.  Read more
Obscure Words. © 2008 by Michael A. Fischer http://home.comcast.net/~wwftd Read more
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