infarction

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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

1. The formation or development of an infarct.
2. An infarct.

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.

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.

Death of an area of tissue because its blood supply has been stopped.

Formation of an infarct See also myocardial infarction.

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.

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Look up infarction in Wiktionary, the free dictionary.

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:

• White infarctions (anemic infarcts) affect solid organs such as the heart, spleen and kidneys wherein the solidity of the tissue (biology) substantially limits the amount of nutrients (blood/oxygen/glucose/fuel) that can flow into the area of ischemic necrosis. Similar occlusion to blood flow and consequent necrosis can occur as a result of severe vasoconstriction as illustrated in severe Raynaud's phenomenon that can lead to irreversible gangrene.
• Red infarctions (hemorrhagic infarcts), generally affect the lungs or other loose organs (testis, ovary, small intestines). The occlusion consists more of red blood cells and fibrin strands. Characteristics of red infarcts include: occlusion of a vein; loose tissues that allow blood to collect in the infarcted zone; tissues with a dual circulatory system (lung, small intestines); tissues previously congested from sluggish venous outflow; and reperfusion (injury)[1] of previously ischemic tissue that is associated with reperfusion-related diseases[2] such as - Myocardial infarction, stroke (cerebral infarction), shock-resuscitation, replantation surgery, frostbite, burns and organ transplantation.

Diseases

Diseases commonly associated with infarctions include:

• Myocardial infarction (heart attack)
• Pulmonary embolism ("lung attack")
• Cerebral infarction (stroke)
• Peripheral artery occlusive disease (the most severe form of which is gangrene)
• Antiphospholipid syndrome
• Sepsis
• Giant-cell arteritis (GCA)
• Hernia
• Volvulus
• Splenic infarction

References

v • d • e Pathology: hemodynamics Decreases Thrombus/thrombosis Renal vein thrombosis Ischemia Brain ischemia · Ischaemic heart disease Infarction general: Anemic infarct · Hemorrhagic infarct regional: Myocardial infarction · Splenic infarction · Cerebral infarction Increases Hemorrhage general Bruise/Hematoma: Petechia · Purpura · Ecchymosis regional: head (Epistaxis, Hemoptysis, Intracranial hemorrhage, Hyphema) · torso (Hemothorax, Hemopericardium) · abdomen (Gastrointestinal bleeding, Haemobilia, Hemoperitoneum, Hematocele, Hematosalpinx ) · joint (Hemarthrosis) Edema general: Anasarca · Angioedema/Lymphedema · Exudate/Transudate regional: Cerebral edema · Pulmonary edema · Hydrothorax · Ascites/hydroperitoneum · Hydrosalpinx Other Hyperemia

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