In medicine, infarction is tissue death caused by a local lack of oxygen, due to an obstruction
of the tissue's blood supply.
The resulting lesion is referred to as an infarct.
Myocardial Infarction is the partial death of heart tissue commonly known as heart attack.
Causes The supplying artery can be blocked by an
obstruction, may be mechanically compressed, ruptured by trauma, or vasoconstricted.
Hypertension and atherosclerosis are risk factors for both atherosclerotic plaques and
thromboembolism.
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 is exposed to circulating
platelets and thrombus formation occurs on the vessel wall occluding blood flow.
Occasionally, the plaque may rupture and form an embolus which travels with the blood-flow
downstream to 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
By histopathology Infarctions are divided into 2 types according
to the amount of blood present: White infarctions affect solid organs such
as the spleen, heart and kidneys wherein the solidity of the tissue substantially limits
the amount of nutrients 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, generally affect the lungs or other loose organs.
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 tissues previously congested from sluggish
venous outflow reperfusion of previously ischemic tissue
that is associated with reperfusion-related diseases, such as myocardial infarction, stroke,
shock-resuscitation, replantation surgery, frostbite, burns, and organ transplantation.
By localization Heart: Myocardial infarction, commonly known
as a heart attack, is an infarction of the heart, causing some heart cells to die.
This is most commonly due to occlusion of a coronary artery following the rupture of
a vulnerable atherosclerotic plaque, which is an unstable collection of lipids and white
blood cells in the wall of an artery.
The resulting ischemia and oxygen shortage, if left untreated for a sufficient period
of time, can cause damage or death of heart muscle tissue.
Brain: Cerebral infarction is the ischemic kind of stroke due to a disturbance in the
blood vessels supplying blood to the brain.
It can be atherothrombotic or embolic.
Stroke caused by cerebral infarction should be distinguished from two other kinds of stroke:
cerebral hemorrhage and subarachnoid hemorrhage.
Cerebral infarctions vary in their severity with one third of the cases resulting in death.
Lung: Pulmonary infarction or lung infarction Spleen: Splenic infarction occurs when the
splenic artery or one of its branches are occluded, for example by a blood clot.
Although it can occur asymptomatically, the typical symptom is severe pain in the left
upper quadrant of the abdomen, sometimes radiating to the left shoulder.
Fever and chills develop in some cases.
It has to be differentiated from other causes of acute abdomen.
Limb: Limb infarction is an infarction of an arm or leg.
Causes include arterial embolisms and skeletal muscle infarction as a rare complication of
long standing, poorly controlled diabetes mellitus.
A major presentation is painful thigh or leg swelling.
Bone: Infarction of bone results in avascular necrosis.
Without blood, the bone tissue dies and the bone collapses.
If avascular necrosis involves the bones of a joint, it often leads to destruction of
the joint articular surfaces.
Testicle: an infarction of a testicle may be caused by testicular torsion.
Eye: an infarction can occur to the central retinal artery which supplies the retina causing
sudden visual loss.
Associated diseases Diseases commonly associated with infarctions
include: Peripheral artery occlusive disease
Antiphospholipid syndrome Sepsis
Giant-cell arteritis Hernia
Volvulus Sickle-cell disease
References
External links Media related to Infarction at Wikimedia Commons
The dictionary definition of infarction at Wiktionary