Ischemia 490305 224407044 2008-07-08T18:39:17Z Basketm 7443500 standardized formatting {{Unreferenced|date=March 2008}} In [[medicine]], '''ischemia''' ([[Greek language|Greek]] '''ισχαιμία''', ''isch-'' is restriction, ''hema'' or ''haema'' is [[blood]]) is a restriction in blood supply, generally due to factors in the [[blood vessel]]s, with resultant damage or dysfunction of tissue. It may also be spelled '''ischaemia''' or '''ischæmia'''. ==Mechanism== Rather than in [[Hypoxia (medical)|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 results in tissue damage because of a lack of oxygen and nutrients. Ultimately, this causes great damage because of a buildup of metabolic wastes. 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: * [[Tachycardia]] (abnormally rapid beating of the [[heart]]) * [[Atherosclerosis]] (lipid-laden plaques obstructing the lumen of [[artery|arteries]]) * [[Hypotension]] (low blood pressure, e.g. in [[septic shock]], heart failure) * [[Thromboembolism]] (blood clots) * Outside compression of a blood vessel, e.g. by a [[tumor]] * [[Embolism]] (foreign bodies in the circulation, e.g. [[amniotic fluid embolism]]) * [[Sickle cell disease]] (abnormally shaped hemoglobin) * Induced [[g-force]]s which restrict the blood flow and force the blood to the extremities of the body, as in aerobatics and military flying ==Consequences== Since oxygen is mainly bound to [[hemoglobin]] in [[red blood cell]]s, insufficient blood supply causes tissue to become hypoxic, or, if no oxygen is supplied at all, [[Hypoxia (medical)|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 disease]]s, [[transient ischemic attack]]s, [[stroke|cerebrovascular accident]]s, ruptured [[arteriovenous malformation]]s, and [[peripheral artery occlusive disease]]. The [[heart]], the [[kidney]]s, and the [[brain]] are among the organs that are the most sensitive to inadequate blood supply. Ischemia in brain tissue, for example due to [[cerebrovascular accident|stroke]] or [[traumatic brain injury|head injury]], causes a process called the [[ischemic cascade]] to be unleashed, in which [[proteolysis|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 [[radical (chemistry)|free radicals]], resulting in [[reperfusion injury]]. With reperfusion injury, necrosis can be greatly accelerated. ==Variations== The mechanism of ischemia depends on the type. One important type is cardiac ischemia, another is bowel ischemia. ===Cardiac ischemia=== <!--Cardiac ischemia redirects here--> Cardiac ischemia may cause chest pain, known as [[angina pectoris]] ====Detection==== Initial evaluation of chest-pain patients involves a 12 lead [[electrocardiogram]] (ECG) and cardiac markers such as [[troponin]]s. 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. ===Bowel ischemia=== An ischemia in the large bowel caused by an inflammation results in [[ischemic colitis]]. An ischemia in the small bowel, on the other hand, caused by an inflammation results in [[mesenteric ischemia]]. ===Cutaneous ischemia=== Reduced blood flow to the skin layers may result in [[mottling]] or uneven, patchy discoloration of the skin. ==Treatment== A [[dietary supplement]] based on [[superoxide dismutase]] and wheat [[gliadin]] (also known as [[glisodin]]) has shown promise in the protection against ischemia-[[reperfusion]] injury by inhibiting oxidative DNA damage.{{Fact|date=June 2008}} ==References== * [http://www.omdict.com/definition/ischemia.php Ischemia definition, causes, treatment and details] <div class="references-small"> <!--See http://en.wikipedia.org/wiki/Wikipedia:Footnotes for an explanation of how to generate footnotes using the <ref(erences/)> tags--> <references/> </div> ==Notes== * Oxford Reference: ''Concise Medical Dictionary'' (1990, 3rd ed.). Oxford University Press: Market House Books. ==See also== * [[Cerebral ischemia]] * [[Infarction]] * [[Ischemic cascade]] * [[Reperfusion injury]] {{pathology}} [[Category:Cardiovascular system]] [[Category:Abdominal pain]] [[ar:إقفار]] [[ca:Isquèmia]] [[cs:Ischemie]] [[de:Ischämie]] [[et:Isheemia]] [[es:Isquemia]] [[fr:Ischémie]] [[hr:Ishemija]] [[it:Ischemia]] [[ku:Îşemî]] [[nl:Ischemie]] [[ja:虚血]] [[no:Iskemi]] [[pl:Niedokrwienie]] [[pt:Isquemia]] [[sl:Ishemija]] [[fi:Iskemia]] [[sv:Ischemi]] [[vi:Thiếu máu cục bộ]] [[ur:اقفار]]