Thrombosis

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Thrombosis
Arterial thrombosis causing cyanosis.jpg
Cyanosis of the lower right extremity, resulting from acute arterial thrombosis of the right leg (on the left side of the image)
Specialty Vascular surgery, internal medicine, pulmonology
Symptoms Dependent on location

Thrombosis (from Ancient Greek θρόμβωσις thrómbōsis "clotting") is the formation of a blood clot inside a blood vessel, obstructing the flow of blood through the circulatory system. When a blood vessel (a vein or an artery) is injured, the body uses platelets (thrombocytes) and fibrin to form a blood clot to prevent blood loss. Even when a blood vessel is not injured, blood clots may form in the body under certain conditions. A clot, or a piece of the clot, that breaks free and begins to travel around the body is known as an embolus. [1] [2]

Contents

Thrombosis may occur in veins (venous thrombosis) or in arteries (arterial thrombosis). Venous thrombosis (sometimes called DVT) leads to a blood clot in the affected part of the body, while arterial thrombosis (and, rarely, severe venous thrombosis) affects the blood supply and leads to damage of the tissue supplied by that artery (ischemia and necrosis). A piece of either an arterial or a venous thrombus can break off as an embolus, which could then travel through the circulation and lodge somewhere else as an embolism. This type of embolism is known as a thromboembolism. Complications can arise when a venous thromboembolism (commonly called a VTE) lodges in the lung as a pulmonary embolism. An arterial embolus may travel further down the affected blood vessel, where it can lodge as an embolism.[ citation needed ]

Signs and symptoms

Thrombosis is generally defined by the type of blood vessel affected (arterial or venous thrombosis) and the precise location of the blood vessel or the organ supplied by it.[ citation needed ]

Venous thrombosis

Deep vein thrombosis

Deep vein thrombosis (DVT) is the formation of a blood clot within a deep vein. It most commonly affects leg veins, such as the femoral vein. Three factors are important in the formation of a blood clot within a deep vein—these are the rate of blood flow, the thickness of the blood and qualities of the vessel wall. Classical signs of DVT include swelling, pain and redness of the affected area.[ citation needed ]

Paget-Schroetter disease

Paget-Schroetter disease or upper extremity DVT (UEDVT) is the obstruction of an arm vein (such as the axillary vein or subclavian vein) by a thrombus. The condition usually comes to light after vigorous exercise and usually presents in younger, otherwise healthy people. Men are affected more than women. [3]

Budd-Chiari syndrome

Budd-Chiari syndrome is the blockage of a hepatic vein or of the hepatic part of the inferior vena cava. This form of thrombosis presents with abdominal pain, ascites and enlarged liver. Treatment varies between therapy and surgical intervention by the use of shunts. [4]

Portal vein thrombosis

Portal vein thrombosis affects the hepatic portal vein, which can lead to portal hypertension and reduction of the blood supply to the liver. [5] It usually happens in the setting of another disease such as pancreatitis, cirrhosis, diverticulitis or cholangiocarcinoma. [6]

Renal vein thrombosis

Renal vein thrombosis is the obstruction of the renal vein by a thrombus. This tends to lead to reduced drainage from the kidney. "Renal vein thrombosis: MedlinePlus Medical Encyclopedia". medlineplus.gov. Retrieved 27 May 2019.</ref>

Cerebral venous sinus thrombosis

Cerebral venous sinus thrombosis (CVST) is a rare form of stroke which results from the blockage of the dural venous sinuses by a thrombus. Symptoms may include headache, abnormal vision, any of the symptoms of stroke such as weakness of the face and limbs on one side of the body and seizures. The diagnosis is usually made with a CT or MRI scan. The majority of persons affected make a full recovery. The mortality rate is 4.3%. [7]

Jugular vein thrombosis

Jugular vein thrombosis is a condition that may occur due to infection, intravenous drug use or malignancy. Jugular vein thrombosis can have a varying list of complications, including: systemic sepsis, pulmonary embolism, and papilledema. Though characterized by a sharp pain at the site of the vein, it can prove difficult to diagnose, because it can occur at random. [8]

Cavernous sinus thrombosis

Cavernous sinus thrombosis is a specialised form of cerebral venous sinus thrombosis, where there is thrombosis of the cavernous sinus of the basal skull dura, due to the retrograde spread of infection and endothelial damage from the danger triangle of the face. The facial veins in this area anastomose with the superior and inferior ophthalmic veins of the orbit, which drain directly posteriorly into the cavernous sinus through the superior orbital fissure. Staphyloccoal or Streptococcal infections of the face, for example nasal or upper lip pustules may thus spread directly into the cavernous sinus, causing stroke-like symptoms of double vision, squint, as well as spread of infection to cause meningitis. "Guidelines Cavernous sinus thrombosis" (PDF).</ref>

Arterial thrombosis

Arterial thrombosis is the formation of a thrombus within an artery. In most cases, arterial thrombosis follows rupture of atheroma (a fat-rich deposit in the blood vessel wall), and is therefore referred to as atherothrombosis. Arterial embolism occurs when clots then migrate downstream and can affect any organ. [9]

Alternatively, arterial occlusion occurs as a consequence of embolism of blood clots originating from the heart ("cardiogenic" emboli). The most common cause is atrial fibrillation, which causes a blood stasis within the atria with easy thrombus formation, but blood clots can develop inside the heart for other reasons too as infective endocarditis.[ citation needed ]

Stroke

Acute thrombus in the right MCA M1 branch ThrombusRtMCAM1Mark.png
Acute thrombus in the right MCA M1 branch

A stroke is the rapid decline of brain function due to a disturbance in the supply of blood to the brain. This can be due to ischemia, thrombus, embolus (a lodged particle) or hemorrhage (a bleed). In thrombotic stroke, a thrombus (blood clot) usually forms around atherosclerotic plaques. Since blockage of the artery is gradual, the onset of symptomatic thrombotic strokes is slower. Thrombotic stroke can be divided into two categories—large vessel disease and small vessel disease. The former affects vessels such as the internal carotids, vertebral and the circle of Willis. The latter can affect smaller vessels such as the branches of the circle of Willis.[ citation needed ]

Myocardial infarction

Myocardial infarction (MI), or heart attack, is caused by ischemia (restriction in the blood supply), which is often due to the obstruction of a coronary artery by a thrombus. This restriction gives an insufficient supply of oxygen to the heart muscle which then results in tissue death (infarction). A lesion is then formed which is the infarct. MI can quickly become fatal if emergency medical treatment is not received promptly. If diagnosed within 12 hours of the initial episode (attack) then thrombolytic therapy is initiated.[ citation needed ]

Limb ischemia

An arterial thrombus or embolus can also form in the limbs, which can lead to acute limb ischemia. [10]

Other sites

Hepatic artery thrombosis usually occurs as a devastating complication after liver transplantation. [11]

Causes

Thrombosis prevention is initiated with assessing the risk for its development. Some people have a higher risk of developing thrombosis and its possible development into thromboembolism. [12] Some of these risk factors are related to inflammation. "Virchow's triad" has been suggested to describe the three factors necessary for the formation of thrombosis: stasis of blood, vessel wall injury, and altered blood coagulation. [13] [14] Some risk factors predispose for venous thrombosis while others increase the risk of arterial thrombosis.[ citation needed ] Newborn babies in the neonatal period are also at risk of a thromboembolism. [15]

Risk factors for thrombosis
FactorNotesReferences
Previous episodes of thrombosis [13]
Vasoconstriction [16]
Slow or turbulent blood flowslow flow is modifiable with exercise [16]
Stroke [17]
Heart failure [17]
Sedentary life stylemodifiable [16]
Plaster casttransient [17]
Dehydration modifiable [16]
Acute respiratory failure [17]
Dysrhythmias [16]
Shock [16]
Obesity modifiable [12] [17] [18] [19] [20]
Pregnancy and the post-partum period [12] [19] [20]
Varicose veins [17] [19]
Surgery [12] [19]
Trauma [12] [17] [19]
Estrogen-based oral contraceptive discontinuation reduces risk [12] [16] [19]
Hormone replacement therapy discontinuation reduces risk [12]
Ovarian hyper-stimulation therapy to treat infertility [12]
Compression of a vein or artery by abnormality, tumor, hematoma [12]
Long surgeries [18]
Pacing wires [19] [21]
Local vein damage, incompetent valves [16] [19] [20]
Central venous catheters [19]
Dialysis catheters [19]
Repetitive motion injury [19]
Immobilitymodifiable risk [17] [19]
Spinal cord injury [19]
Age [12] [16] [17] [19]
Cancers [19]
Sepsis [19]
Polycythemia [19]
Protein C and/or S deficiencycongenital; associated with Warfarin necrosis [19]
Antiphospholipid antibody syndrome altered coagulation [19]
Factor V Leiden defectaltered coagulation [19]
Prothrombin G20210A defectaltered coagulation [19]
Elevated PAI-1 inhibits physiological breakdown of blood clots [22]
Hyperhomocysteinemia altered coagulation [19]
Elevated factors II, VIII, IX, XI altered coagulation [19]
Antithrombin III deficiency altered coagulation [19]
Falls and hip fracturerelated to immobility [23]
Selective estrogen-receptor modulators [12]
Erythropoiesis-stimulating agents [12]
Acute medical illness [12]
Inflammatory bowel disease [12]
Nephrotic syndrome [12]
Myeloproliferative disorders [12]
Paroxysmal nocturnal hemoglobinnuria [12]
Thrombophilias [12]
Post-menopausal hormone replacement therapydiscontinuation reduces risk [12]
Right heart failure [20]
Venous inflammation/phlebitiswhen a thrombus forms, it is thrombophlebitis [16]
Ambient air pollutionthought to be related to inflammation [24] [25] [26]

Mechanism

Pathogenesis

The main causes of thrombosis are given in Virchow's triad which lists thrombophilia, endothelial cell injury, and disturbed blood flow. Generally speaking the risk for thrombosis increases over the life course of individuals, depending on life style factors like smoking, diet, and physical activity, the presence of other diseases like cancer or autoimmune disease, while also platelet properties change in aging individuals which is an important consideration as well. [27]

Hypercoagulability

Hypercoagulability or thrombophilia, is caused by, for example, genetic deficiencies or autoimmune disorders. Recent studies indicate that white blood cells play a pivotal role in deep vein thrombosis, mediating numerous pro-thrombotic actions. [28]

Endothelial cell injury

Any inflammatory process, such as trauma, surgery or infection, can cause damage to the endothelial lining of the vessel's wall. The main mechanism is exposure of tissue factor to the blood coagulation system. [29] Inflammatory and other stimuli (such as hypercholesterolemia) can lead to changes in gene expression in endothelium producing to a pro-thrombotic state. [30] When this occurs, endothelial cells downregulate substances such as thrombomodulin, which is a key modulator of thrombin activity. [31] The result is a sustained activation of thrombin and reduced production of protein C and tissue factor inhibitor, which furthers the pro-thrombotic state. [30]

Endothelial injury is almost invariably involved in the formation of thrombi in arteries, as high rates of blood flow normally hinder clot formation. In addition, arterial and cardiac clots are normally rich in platelets–which are required for clot formation in areas under high stress due to blood flow. [30]

Disturbed blood flow

Cancer-associated thrombosis can result from: (1) stasis, i.e., direct pressure on blood vessels by the tumor mass, poor performance status, and bed rest following surgical procedures; (2) iatrogenic, due to treatment with antineoplastic medications; and (3) secretion of heparanase from malignant tumors that results in degradation of endogenous heparin. Source: Potential Mechanisms of Cancer-Related Hypercoagulability. Nasser NJ, Fox J, Agbarya A. Cancers (Basel). 2020 Feb 29;12(3):566. https://doi.org/10.3390/cancers12030566 Potential Mechanisms of Cancer-Related Hypercoagulability.png
Cancer-associated thrombosis can result from: (1) stasis, i.e., direct pressure on blood vessels by the tumor mass, poor performance status, and bed rest following surgical procedures; (2) iatrogenic, due to treatment with antineoplastic medications; and (3) secretion of heparanase from malignant tumors that results in degradation of endogenous heparin. Source: Potential Mechanisms of Cancer-Related Hypercoagulability. Nasser NJ, Fox J, Agbarya A. Cancers (Basel). 2020 Feb 29;12(3):566. https://doi.org/10.3390/cancers12030566

Causes of disturbed blood flow include stagnation of blood flow past the point of injury, or venous stasis which may occur in heart failure, [29] or after long periods of sedentary behaviour, such as sitting on a long airplane flight. Also, atrial fibrillation, causes stagnant blood in the left atrium (LA), or left atrial appendage (LAA), and can lead to a thromboembolism. [29] Cancers or malignancies such as leukemia may cause increased risk of thrombosis by possible activation of the coagulation system by cancer cells or secretion of procoagulant substances (paraneoplastic syndrome), by external compression on a blood vessel when a solid tumor is present, or (more rarely) extension into the vasculature (for example, renal cell cancers extending into the renal veins). [29] Also, treatments for cancer (radiation, chemotherapy) often cause additional hypercoagulability. [29] There are scores that correlate different aspects of patient data (comorbidities, vital signs, and others) to risk of thrombosis, such as the POMPE-C, which stratifies risk of mortality due to pulmonary embolism in patients with cancer, who typically have higher rates of thrombosis. [33] Also, there are several predictive scores for thromboembolic events, such as Padua, [34] Khorana, [35] [36] and ThroLy score. [37]

Pathophysiology

Natural history

Fibrinolysis is the physiological breakdown of blood clots by enzymes such as plasmin.

Organisation: following the thrombotic event, residual vascular thrombus will be re-organised histologically with several possible outcomes. For an occlusive thrombus (defined as thrombosis within a small vessel that leads to complete occlusion), wound healing will reorganise the occlusive thrombus into collagenous scar tissue, where the scar tissue will either permanently obstruct the vessel, or contract down with myofibroblastic activity to unblock the lumen. For a mural thrombus (defined as a thrombus in a large vessel that restricts the blood flow but does not occlude completely), histological reorganisation of the thrombus does not occur via the classic wound healing mechanism. Instead, the platelet-derived growth factor degranulated by the clotted platelets will attract a layer of smooth muscle cells to cover the clot, and this layer of mural smooth muscle will be vascularised by the blood inside the vessel lumen rather than by the vasa vasorum.[ citation needed ]

Ischemia/infarction: if an arterial thrombus cannot be lysed by the body and it does not embolise, and if the thrombus is large enough to impair or occlude blood flow in the involved artery, then local ischemia or infarction will result. A venous thrombus may or may not be ischemic, since veins distribute deoxygenated blood that is less vital for cellular metabolism. Nevertheless, non-ischemic venous thrombosis may still be problematic, due to the swelling caused by blockage to venous drainage. In deep vein thrombosis this manifests as pain, redness, and swelling; in retinal vein occlusion this may result in macular oedema and visual acuity impairment, which if severe enough can lead to blindness.

Embolization

A thrombus may become detached and enter circulation as an embolus, finally lodging in and completely obstructing a blood vessel, which unless treated very quickly will lead to tissue necrosis (an infarction) in the area past the occlusion. Venous thrombosis can lead to pulmonary embolism when the migrated embolus becomes lodged in the lung. In people with a "shunt" (a connection between the pulmonary and systemic circulation), either in the heart or in the lung, a venous clot can also end up in the arteries and cause arterial embolism.[ citation needed ]

Arterial embolism can lead to obstruction of blood flow through the blood vessel that is obstructed by it, and a lack of oxygen and nutrients (ischemia) of the downstream tissue. The tissue can become irreversibly damaged, a process known as necrosis. This can affect any organ; for instance, arterial embolism of the brain is one of the causes of stroke.[ citation needed ]

Prevention

The use of heparin following surgery is common if there are no issues with bleeding. Generally, a risk-benefit analysis is required, as all anticoagulants lead to an increased risk of bleeding. [38] In people admitted to hospital, thrombosis is a major cause for complications and occasionally death. In the UK, for instance, the Parliamentary Health Select Committee heard in 2005 that the annual rate of death due to thrombosis was 25,000, with at least 50% of these being hospital-acquired. [39] Hence thromboprophylaxis (prevention of thrombosis) is increasingly emphasized. In patients admitted for surgery, graded compression stockings are widely used, and in severe illness, prolonged immobility and in all orthopedic surgery, professional guidelines recommend low molecular weight heparin (LMWH) administration, mechanical calf compression or (if all else is contraindicated and the patient has recently developed deep vein thrombosis) the insertion of a vena cava filter. [40] [41] In patients with medical rather than surgical illness, LMWH too is known to prevent thrombosis, [41] [42] and in the United Kingdom the Chief Medical Officer has issued guidance to the effect that preventative measures should be used in medical patients, in anticipation of formal guidelines. [39]

Treatment

The treatment for thrombosis depends on whether it is in a vein or an artery, the impact on the person, and the risk of complications from treatment.

Anticoagulation

Warfarin and vitamin K antagonists are anticoagulants that can be taken orally to reduce thromboembolic occurrence. Where a more effective response is required, heparin can be given (by injection) concomitantly. As a side effect of any anticoagulant, the risk of bleeding is increased, so the international normalized ratio of blood is monitored. Self-monitoring and self-management are safe options for competent patients, though their practice varies. In Germany, about 20% of patients were self-managed while only 1% of U.S. patients did home self-testing (according to one 2012 study). [43] Other medications such as direct thrombin inhibitors and direct Xa inhibitors are increasingly being used instead of warfarin.[ citation needed ]

Thrombolysis

Thrombolysis is the pharmacological destruction of blood clots by administering thrombolytic drugs including recombinant tissue plasminogen activator, which enhances the normal destruction of blood clots by the body's enzymes. This carries an increased risk of bleeding so is generally only used for specific situations (such as severe stroke or a massive pulmonary embolism). [44]

Surgery

Arterial thrombosis may require surgery if it causes acute limb ischemia.[ citation needed ]

Endovascular treatment

Mechanical clot retrieval and catheter-guided thrombolysis are used in certain situations. [45]

Antiplatelet agents

Arterial thrombosis is platelet-rich, and inhibition of platelet aggregation with antiplatelet drugs such as aspirin may reduce the risk of recurrence or progression. [46]

Targeting ischemia/reperfusion injury

With reperfusion comes ischemia/reperfusion (IR) injury (IRI), which paradoxically causes cell death in reperfused tissue [47] and contributes significantly to post-reperfusion mortality and morbidity. [48] [49] For example, in a feline model of intestinal ischemia, four hours of ischemia resulted in less injury than three hours of ischemia followed by one hour of reperfusion. [47] In ST-elevation myocardial infarction (STEMI), IRI contributes up to 50% of final infarct size despite timely primary percutaneous coronary intervention. This is a key reason for the continued high mortality and morbidity in these conditions, despite endovascular reperfusion treatments and continuous efforts to improve timeliness and access to these treatments. Hence, protective therapies are required to attenuate IRI alongside reperfusion in acute ischemic conditions to improve clinical outcomes. [50] Therapeutic strategies that have potential to improve clinical outcomes in reperfused STEMI patients include remote ischemic conditioning (RIC), exenatide, and metoprolol. These have emerged amongst a multitude of cardioprotective interventions investigated with largely neutral clinical data. [51] Of these, RIC has the most robust clinical evidence, especially in the context of STEMI, but also emerging for other indications such as acute ischemic stroke and aneurysmal subarachnoid hemorrhage. [50]

Neonatal thrombosis

Treatment options for full-term and preterm babies who develop thromboembolism include expectant management (with careful observation), nitroglycerin ointment, pharmacological therapy (thrombolytics and/or anticoagulants), and surgery. [15] The evidence supporting these treatment approaches is weak. For anticoagulant treatment, t is not clear if unfractionated and/or low molecular weight heparin treatment is effective at decreasing mortality and serious adverse events in this population. [15] There is also insufficient evidence to understand the risk of adverse effects associated with these treatment approaches in term or preterm infants. [15]

See also

Related Research Articles

Embolism Disease of arteries, arterioles and capillaries

An embolism is the lodging of an embolus, a blockage-causing piece of material, inside a blood vessel. The embolus may be a blood clot (thrombus), a fat globule, a bubble of air or other gas, amniotic fluid, or foreign material. An embolism can cause partial or total blockage of blood flow in the affected vessel. Such a blockage may affect a part of the body distant from the origin of the embolus. An embolism in which the embolus is a piece of thrombus is called a thromboembolism.

Embolus Unattached mass that travels through the bloodstream

An embolus is an unattached mass that travels through the bloodstream and is capable of creating blockages. When an embolus occludes a blood vessel, it is called an embolism or embolic event. There are a number of different types of emboli, including blood clots, cholesterol plaque or crystals, fat globules, gas bubbles, and foreign bodies, which can result in different types of embolisms.

Thrombus Blood clot

A thrombus, colloquially called a blood clot, is the final product of the blood coagulation step in hemostasis. There are two components to a thrombus: aggregated platelets and red blood cells that form a plug, and a mesh of cross-linked fibrin protein. The substance making up a thrombus is sometimes called cruor. A thrombus is a healthy response to injury intended to stop and prevent further bleeding, but can be harmful in thrombosis, when a clot obstructs blood flow through healthy blood vessels in the circulatory system.

Venous thrombosis Blood clot (thrombus) that forms within a vein

Venous thrombosis is blockage of a vein caused by a thrombus. A common form of venous thrombosis is deep vein thrombosis (DVT), when a blood clot forms in the deep veins. If a thrombus breaks off (embolizes) and flows to the lungs to lodge there, it becomes a pulmonary embolism (PE), a blood clot in the lungs. The conditions of DVT only, DVT with PE, and PE only, are all captured by the term venous thromboembolism (VTE).

Factor V Leiden is a variant of human factor V, which causes an increase in blood clotting (hypercoagulability). Due to this mutation, protein C, an anticoagulant protein that normally inhibits the pro-clotting activity of factor V, is not able to bind normally to factor V, leading to a hypercoagulable state, i.e., an increased tendency for the patient to form abnormal and potentially harmful blood clots. Factor V Leiden is the most common hereditary hypercoagulability disorder amongst ethnic Europeans. It is named after the Dutch city of Leiden, where it was first identified in 1994 by Rogier Maria Bertina under the direction of Pieter Hendrick Reitsma. Despite the increased risk of venous thromboembolisms, people with one copy of this gene have not been found to have shorter lives than the general population.

Ischemia Restriction in blood supply to tissues

Ischemia or ischaemia is a restriction in blood supply to any tissues, muscle group, or organ of the body, causing a shortage of oxygen that is needed for cellular metabolism. Ischemia is generally caused by problems with blood vessels, with resultant damage to or dysfunction of tissue i.e. hypoxia and microvascular dysfunction. It also means local hypoxia in a given part of a body sometimes resulting from constriction. Ischemia comprises not only insufficiency of oxygen, but also reduced availability of nutrients and inadequate removal of metabolic wastes. Ischemia can be partial or total blockage. The inadequate delivery of oxygenated blood to the organs must be resolved either by treating the cause of the inadequate delivery or reducing the oxygen demand of the system that needs it. For example, patients with myocardial ischemia have a decreased blood flow to the heart and are prescribed with medications that reduce chronotrophy and ionotrophy to meet the new level of blood delivery supplied by the stenosed so that it is adequate.

Thrombolysis Breakdown (lysis) of blood clots formed in blood vessels, using medication

Thrombolysis, also called fibrinolytic therapy, is the breakdown (lysis) of blood clots formed in blood vessels, using medication. It is used in ST elevation myocardial infarction, stroke, and in cases of severe venous thromboembolism.

Deep vein thrombosis Formation of a blood clot (thrombus) in a deep vein

Deep vein thrombosis (DVT) is a type of venous thrombosis involving the formation of a blood clot in a deep vein, most commonly in the legs or pelvis. A minority of DVTs occur in the arms. Symptoms can include pain, swelling, redness, and enlarged veins in the affected area, but some DVTs have no symptoms. The most common life-threatening concern with DVT is the potential for a clot to embolize, travel as an embolus through the right side of the heart, and become lodged in a pulmonary artery that supplies blood to the lungs. This is called a pulmonary embolism (PE). DVT and PE comprise the cardiovascular disease of venous thromboembolism (VTE). About two-thirds of VTE manifests as DVT only, with one-third manifesting as PE with or without DVT. The most frequent long-term DVT complication is post-thrombotic syndrome, which can cause pain, swelling, a sensation of heaviness, itching, and in severe cases, ulcers. Recurrent VTE occurs in about 30% of those in the ten years following an initial VTE.

Infarction Tissue death due to inadequate blood supply

Infarction is tissue death (necrosis) due to inadequate blood supply to the affected area. It may be caused by artery blockages, rupture, mechanical compression, or vasoconstriction. The resulting lesion is referred to as an infarct (from the Latin infarctus, "stuffed into").

Coronary thrombosis Medical condition

Coronary thrombosis is defined as the formation of a blood clot inside a blood vessel of the heart. This blood clot may then restrict blood flow within the heart, leading to heart tissue damage, or a myocardial infarction, also known as a heart attack.

Cerebral infarction Medical condition

A cerebral infarction is the pathologic process that results in an area of necrotic tissue in the brain. It is caused by disrupted blood supply (ischemia) and restricted oxygen supply (hypoxia), most commonly due to thromboembolism, and manifests clinically as ischemic stroke. In response to ischemia, the brain degenerates by the process of liquefactive necrosis.

An embolus, is described as a free-floating mass, located inside blood vessels that can travel from one site in the blood stream to another. An embolus can be made up of solid, liquid, or gas. Once these masses get "stuck" in a different blood vessel, it is then known as an "embolism." An embolism can cause ischemia - or damage to an organ from lack of oxygen. A paradoxical embolism is a specific type of embolism in which the emboli travels from the right side of the heart or "venous circulation," travels to the left side of the heart or "arterial circulation," and lodges itself in a blood vessel known as an artery. Thus, it is termed "paradoxical" because the emboli lands in an artery, rather than a vein.

Compression stockings Compression garment

Compression stockings are a specialized hosiery designed to help prevent the occurrence of, and guard against further progression of, venous disorders such as edema, phlebitis and thrombosis. Compression stockings are elastic compression garments worn around the leg, compressing the limb. This reduces the diameter of distended veins and increases venous blood flow velocity and valve effectiveness. Compression therapy helps decrease venous pressure, prevents venous stasis and impairments of venous walls, and relieves heavy and aching legs.

Ocular ischemic syndrome is the constellation of ocular signs and symptoms secondary to severe, chronic arterial hypoperfusion to the eye. Amaurosis fugax is a form of acute vision loss caused by reduced blood flow to the eye; it may be a warning sign of an impending stroke, as both stroke and retinal artery occlusion can be caused by thromboembolism due to atherosclerosis elsewhere in the body. Consequently, those with transient blurring of vision are advised to urgently seek medical attention for a thorough evaluation of the carotid artery. Anterior segment ischemic syndrome is a similar ischemic condition of anterior segment usually seen in post-surgical cases. Retinal artery occlusion leads to rapid death of retinal cells, thereby resulting in severe loss of vision.

Embolectomy is the emergency surgical removal of emboli which are blocking blood circulation. It usually involves removal of thrombi, and is then referred to as thrombectomy. Embolectomy is an emergency procedure often as the last resort because permanent occlusion of a significant blood flow to an organ leads to necrosis. Other involved therapeutic options are anticoagulation and thrombolysis.

Acute limb ischaemia Occurs when there is a sudden lack of blood flow to a limb

Acute limb ischaemia (ALI) occurs when there is a sudden lack of blood flow to a limb.

Arterial embolism Interruption of blood flow to an organ

Arterial embolism is a sudden interruption of blood flow to an organ or body part due to an embolus adhering to the wall of an artery blocking the flow of blood, the major type of embolus being a blood clot (thromboembolism). Sometimes, pulmonary embolism is classified as arterial embolism as well, in the sense that the clot follows the pulmonary artery carrying deoxygenated blood away from the heart. However, pulmonary embolism is generally classified as a form of venous embolism, because the embolus forms in veins. Arterial embolism is the major cause of infarction.

Blood clots are a relatively common occurrence in the general population and are seen in approximately 1-2% of the population by age 60. Typically blood clots develop in the deep veins of the lower extremities, deep vein thrombosis (DVT) or as a blood clot in the lung, pulmonary embolism (PE). A very small number of people who develop blood clots have a more serious and often life-threatening condition, known as Thrombotic Storm (TS). TS is characterized by the development of more than one blood clot in a short period of time. These clots often occur in multiple and sometimes unusual locations in the body and are often difficult to treat. TS may be associated with an existing condition or situation that predisposes a person to blood clots such as injury, infection, or pregnancy. In many cases a risk assessment will identify interventions that will prevent the formation of blood clots.

Thrombosis prevention Medical treatment

Thrombosis prevention or thromboprophylaxis is medical treatment to prevent the development of thrombosis in those considered at risk for developing thrombosis. Some people are at a higher risk for the formation of blood clots than others. Prevention measures or interventions are usually begun after surgery as people are at higher risk due to immobility.

Arterial occlusion

Arterial occlusion is a condition involving partial or complete blockage of blood flow through an artery. Arteries are blood vessels that carry oxygenated blood to body tissues. An occlusion of arteries disrupts oxygen and blood supply to tissues, leading to ischemia. Depending on the extent of ischemia, symptoms of arterial occlusion range from simple soreness and pain that can be relieved with rest, to a lack of sensation or paralysis that could require amputation.

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