ischemic

In medicine, ischemia (Greek ισχαιμία, isch- is restriction, hema or haema is blood) is a restriction in blood supply, generally due to factors in the blood vessels, with resultant damage or dysfunction of tissue. It may also be spelled ischaemia or ischæmia.

Mechanism

Rather than in hypoxia, a more general term denoting a shortage of oxygen (usually a result of lack of oxygen in the air being breathed), ischemia is an absolute or relative shortage of the blood supply to an organ. Relative shortage means the mismatch of blood supply (oxygen delivery) and blood request for adequate oxygenation of tissue.

Ischemia can also be described as an inadequate flow of blood to a part of the body, caused by constriction or blockage of the blood vessels supplying it. Ischemia of heart muscle produces angina pectoris.

This can be due to:

Consequences

Since oxygen is mainly bound to hemoglobin in red blood cells, insufficient blood supply causes tissue to become hypoxic, or, if no oxygen is supplied at all, anoxic. This can cause necrosis (i.e. cell death). In very aerobic tissues such as heart and brain, at body temperature Necrosis due to ischemia usually takes about 3-4 hours before becoming irreversible. This and typically some collateral circulation to the ischemic area accounts for the efficacy of "clot-buster" drugs such as Alteplase, given for stroke and heart-attack within this time period. However, complete cessation of oxygenation of such organs for more than 20 minutes typically results in irreversible damage.

Ischemia is a feature of heart diseases, transient ischemic attacks, cerebrovascular accidents, ruptured arteriovenous malformations, and peripheral artery occlusive disease. The heart, the kidneys, and the brain are among the organs that are the most sensitive to inadequate blood supply. Ischemia in brain tissue, for example due to stroke or head injury, causes a process called the ischemic cascade to be unleashed, in which proteolytic enzymes, reactive oxygen species, and other harmful chemicals damage and may ultimately kill brain tissue.

Restoration of blood flow after a period of ischemia can actually be more damaging than the ischemia. Reintroduction of oxygen causes a greater production of damaging free radicals, resulting in reperfusion injury. With reperfusion injury, necrosis can be greatly accelerated.

Detection of cardiac ischemia

Initial evaluation of chest-pain patients involves a 12 lead electrocardiogram (ECG) and cardiac markers such as troponins. These tests are highly specific but very insensitive and often leave the requirement for further testing to achieve an accurate diagnosis. Magnetocardiography (MCG) imaging utilises superconducting quantum interference devices (SQUIDs) to detect the weak magnetic fields generated by the heart's electrical fields. There is a direct correlation between abnormal cardiac depolarisation or repolarisation and abnormality in the magnetic field map. In July 2004, the Food and Drug Administration (FDA) approved the CardioMag Imaging MCG as a safe device for the non-invasive detection of ischemia.

References

Notes

  • Oxford Reference: Concise Medical Dictionary (1990, 3rd ed.). Oxford University Press: Market House Books.

See also

Medicine is the science and "" of maintaining and/or restoring human health through the study, diagnosis, and treatment of patients. The term is derived from the Latin ars medicina meaning the art of healing.
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Greek}}} 
Writing system: Greek alphabet 
Official status
Official language of:  Greece
 Cyprus
 European Union
recognised as minority language in parts of:
 European Union
 Italy
 Turkey
Regulated by:
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Blood is a specialized biological fluid consisting of red blood cells (also called RBCs or erythrocytes), white blood cells (also called leukocytes) and platelets (also called thrombocytes) suspended in a complex fluid medium known as blood plasma.
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The blood vessels are part of the cardiovascular system and function to transport blood throughout the body. The most important types, arteries and veins, carry blood away from or towards the heart, respectively.
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For other uses of the term "hypoxia", see hypoxia.


Hypoxia is a pathological condition in which the body as a whole (generalised hypoxia) or region of the body (tissue hypoxia) is deprived of adequate oxygen supply.
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MeSH D000787
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Tachycardia
Classifications and external resources

ICD-10 R 00.0
ICD-9 785.0

MeSH D013610 Tachycardia is a form of cardiac arrhythmia which refers to a rapid beating of the heart.
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heart is a muscular organ responsible for pumping blood through the blood vessels by repeated, rhythmic contractions, or a similar structure in the annelids, mollusks, and arthropods.
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Atherosclerosis
Classification & external resources

Changes in endothelial dysfunction in atherosclerosis (note text comments about geometry error)
ICD-10 I 70.
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Arteries are muscular blood vessels that carry blood away from the heart.[1] All arteries, with the exception of the pulmonary and umbilical arteries, carry oxygenated blood.

The circulatory system is extremely important for sustaining life.
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MeSH D007022

In physiology and medicine, hypotension refers to an abnormally low blood pressure. This is best understood as a physiologic state, rather than a disease. It is often associated with shock, though not necessarily indicative of it.
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Septic shock
Classification & external resources

ICD-10 A41.9
ICD-9 785.52

Septic shock is a serious medical condition caused by decreased tissue perfusion and oxygen delivery as a result of infection and sepsis.
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MeSH D013927 Thrombosis is the formation of a clot or thrombus inside a blood vessel, obstructing the flow of blood through the circulatory system. Thromboembolism is a general term describing both thrombosis and its main complication which is embolisation.
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Tumor or tumour (via Old French tumour from Latin tumor "swelling") is an abnormal growth or mass of tissue. A tumor can be either malignant or benign.
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Amniotic fluid is the watery liquid surrounding and cushioning a growing fetus within the amnion. It allows the fetus to move freely without the walls of the uterus being too tight against its body. Buoyancy is also provided.
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Amniotic fluid embolism (AFE) is a rare and incompletely understood obstetric emergency in which amniotic fluid, fetal cells, hair or other debris enters the mother's blood stream via the placental bed of the uterus and triggers an allergic reaction.
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Sickle cells
Classification & external resources

Sickle-shaped red blood cells
ICD-10 D 57.
ICD-9 282.6

OMIM 603903
DiseasesDB 1206
MedlinePlus 000527
eMedicine emerg/26  

MeSH C15.378.071.141.150.
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g-force (also g-load) is a measurement of an object's acceleration expressed in g's. It may also informally refer to the reaction force resulting from an acceleration, with the causing acceleration expressed in g's.
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Hemoglobin, also spelled haemoglobin and abbreviated Hb, is the iron-containing oxygen-transport metalloprotein in the red blood cells of the blood in vertebrates and other animals.
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Red blood cells are the most common type of blood cell and the vertebrate body's principal means of delivering oxygen from the lungs or gills to body tissues via the blood.
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For other uses of the term "hypoxia", see hypoxia.


Hypoxia is a pathological condition in which the body as a whole (generalised hypoxia) or region of the body (tissue hypoxia) is deprived of adequate oxygen supply.
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Necrosis (in Greek Νεκρός = Dead) is the name given to accidental death of cells and living tissue. Necrosis is less orderly than apoptosis, which is part of programmed cell death.
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Necrosis (in Greek Νεκρός = Dead) is the name given to accidental death of cells and living tissue. Necrosis is less orderly than apoptosis, which is part of programmed cell death.
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Tissue plasminogen activator (abbreviated PLAT or tPA) is a secreted serine protease which converts the proenzyme plasminogen to plasmin, a fibrinolytic enzyme.
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Heart disease is an umbrella term for a number of different diseases which affect the heart and as of 2007 it is the leading cause of death in the United States.[1]

Types of heart disease

Cardiomyopathy


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Transient ischemic attack
Classification & external resources

ICD-10 G 45.9
ICD-9 435.9

DiseasesDB 13253
MedlinePlus 000730
eMedicine emerg/604  
MeSH D002546

A transient ischemic attack (TIA
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Stroke
Classification & external resources

ICD-10 I 61. -I 64.
ICD-9 435 - 436

OMIM 601367
DiseasesDB 2247
MedlinePlus 000726pi
eMedicine neuro/9   emerg/558 emerg/557 pmr/187
MeSH D020521

Stroke (or
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MeSH D001165

Arteriovenous malformation or AVM is a congenital disorder of the connections between veins and arteries in the vascular system. The genetic transmission patterns of AVM (if any) are unknown, and AVM is not generally thought to be an inherited
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In medicine, peripheral artery occlusive disease (PAOD, also known as peripheral vascular disease (PVD) and peripheral artery disease (PAD) is a collator for all diseases caused by the obstruction of large peripheral arteries, which can result from atherosclerosis,
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heart is a muscular organ responsible for pumping blood through the blood vessels by repeated, rhythmic contractions, or a similar structure in the annelids, mollusks, and arthropods.
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