thromboembolism

　

WordNet

1. occlusion of a blood vessel by an embolus that has broken away from a thrombus

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2014/01/30 19:30:03」(JST)

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Thrombosis
Classification and external resources
Cyanosis of the lower right extremity, resulting from acute arterial thrombosis of the right leg
ICD-10	I80-I82
ICD-9	437.6, 453, 671.5, 671.9
MeSH	D013927

Thrombosis (Greek: θρόμβωσις) is the formation of a blood clot (thrombus; Greek: θρόμβος) inside a blood vessel, obstructing the flow of blood through the circulatory system. When a blood vessel 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 that breaks free and begins to travel around the body is known as an embolus.

When a thrombus is significantly large enough to reduce the blood flow to a tissue, hypoxia (oxygen deprivation) can occur and metabolic products such as lactic acid can accumulate. A larger thrombus causing a much greater obstruction to the blood flow may result in anoxia, the complete deprivation of oxygen and infarction, tissue death. There are also a number of other conditions that can arise according to the location of the thrombus and the organs affected.

Thromboembolism is the combination of thrombosis and its main complication, embolism.

Causes

In classical terms, thrombosis is caused by abnormalities in one or more of the following (Virchow's triad):

• The composition of the blood (hypercoagulability or thrombophilia)
• Quality of the vessel wall (endothelial cell injury)
• Nature of the blood flow (stasis, turbulence)

Hypercoagulability

Main article: Thrombophilia

Hypercoagulability is caused by, for example, genetic deficiencies or autoimmune disorders. Recent studies indicate that neutrophils play a pivotal role in deep vein thrombosis, mediating numerous pro-thrombotic actions

Endothelial cell injury

Causes of injury to the vessel's wall include trauma, surgery, infection or turbulent flow at bifurcations. The main mechanism is exposure of tissue factor to the blood coagulation system.

Disturbed blood flow

Further information: Blood flow

Causes of disturbed blood flow include stagnation of blood flow past the point of injury, or venous stasis which may occur in heart failure, in or after long periods of sedentary behavior, 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. 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). Also, treatments for cancer (radiation, chemotherapy) often cause additional hypercoagulability.

Classification

There are two distinct forms of thrombosis, venous thrombosis and arterial thrombosis, each of which can be presented by several subtypes.

Venous thrombosis

Main article: Venous thrombosis

Venous thrombosis is the formation of a thrombus (blood clot) within a vein. There are several diseases which can be classified under this category:

Deep vein thrombosis

Main article: 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.

Portal vein thrombosis

Main article: 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. It usually has a pathological cause such as pancreatitis, cirrhosis, diverticulitis or cholangiocarcinoma.

Renal vein thrombosis

Main article: 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. Anticoagulation therapy is the treatment of choice.

Jugular vein thrombosis

Main article: 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.

Budd-Chiari syndrome

Main article: Budd-Chiari syndrome

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

Paget-Schroetter disease

Main article: Paget-Schroetter disease

Paget-Schroetter disease is the obstruction of an upper extremity 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.

Cerebral venous sinus thrombosis

Main article: 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%.

Arterial thrombosis

Arterial thrombosis is the formation of a thrombus within an artery. In most cases, arterial thrombosis follows rupture of atheroma, and is therefore referred to as atherothrombosis.

Another common cause of arterial occlusion is atrial fibrillation, which causes a blood stasis within the atria with easy thrombus formation. In addition, it is well known that the direct current cardioversion of atrial fibrillation carries a great risk of thromboembolism, especially if persisting more than 48 hours. Thromboembolism strikes approximately 5% of cases not receiving anticoagulant therapy. When cardiac rhythm is restored clots are pushed out from atria to ventricles and from these to the aorta and its branches.

Arterial thrombosis can embolize and is a major cause of arterial embolism, potentially causing infarction of almost any organ in the body.

Stroke

Main article: Stroke

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, 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.

Myocardial infarction

Main article: Myocardial infarction

Myocardial infarction (MI) or heart attack, is caused by ischemia, (restriction in the blood supply), 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.

Other sites

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

An arterial embolus can also form in the limbs.

Embolization

If a bacterial infection is present at the site of thrombosis, the thrombus may break down, spreading particles of infected material throughout the circulatory system (pyemia, septic embolus) and setting up metastatic abscesses wherever they come to rest. Without an infection, the 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. If the occlusion is in the coronary artery, myocardial ischaemia is likely to occur, whereby cardiac myocytes cannot function properly due to lack of oxygen. This lack of oxygen is then likely to result in a myocardial infarction.

Most thrombi, however, become organized into fibrous tissue, and the thrombosed vessel is gradually recanalized.

Prevention

Prophylaxis of venous thromboembolism with heparin in medical patients does not appear to decrease mortality and while it may decrease the risk of pulmonary embolism and deep vein thrombosis it increases the risk of bleeding and thus results in little or no overall clinical benefit. Mechanical measures also appeared of little benefit in this group and in those with a stroke resulted in harm. Evidence supports the use of heparin following surgery which has a high risk of thrombosis to reduce the risk of DVTs; however the effect on PEs or overall mortality is not known.

Generally, a risk-benefit analysis is required, as all anticoagulants lead to a small increase in the risk of major bleeding. In atrial fibrillation, for instance, the risk of stroke (calculated on the basis of additional risk factors, such as advanced age and high blood pressure) needs to outweigh the small but known risk of major bleeding associated with the use of warfarin.

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. 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 suffered deep vein thrombosis) the insertion of a vena cava filter. In patients with medical rather than surgical illness, LMWH too is known to prevent thrombosis, 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.

Treatment

Coumarins, 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.

See also

• National Blood Clot Alliance
• Blood clotting tests

References

External links

• Media related to Thrombosis at Wikimedia Commons

UpToDate Contents

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• 1. 静脈血栓症の原因の概要 overview of the causes of venous thrombosis
• 2. 静脈血栓塞栓症の患者における理論的根拠と無期限の抗凝固の適応 rationale and indications for indefinite anticoagulation in patients with venous thromboembolism
• 3. 下肢深部静脈血栓症の治療の概要 overview of the treatment of lower extremity deep vein thrombosis dvt
• 4. 急性肺塞栓症の抗凝固療法 anticoagulation in acute pulmonary embolism
• 5. 成人癌患者における静脈血栓塞栓症のリスクおよび予防 risk and prevention of venous thromboembolism in adults with cancer

English Journal

• Effects of clopidogrel therapy on whole blood platelet aggregation, the Plateletworks® assay and coagulation parameters in cats with asymptomatic hypertrophic cardiomyopathy: a pilot study.

• den Toom ML1, van Leeuwen MW1, Szatmári V1, Teske E1.
• The Veterinary quarterly.Vet Q.2017 Dec;37(1):8-15. Epub 2016 Oct 27.
• BACKGROUND: Although scientific evidence is limited, clopidogrel is frequently used as prophylaxis for arterial thromboembolism in cats with hypertrophic cardiomyopathy (HCM).OBJECTIVES: Evaluating effects of clopidogrel therapy in asymptomatic cats with HCM on (1) conventional whole blood aggregati
• PMID 27786603

• Baseline and treatment-related changes in thrombin generation in patients with multiple myeloma.

• Tiong IS1,2, Rodgers SE1,3, Lee CH1,2,4, McRae SJ1,3,4.
• Leukemia & lymphoma.Leuk Lymphoma.2017 Apr;58(4):941-949. doi: 10.1080/10428194.2016.1219900. Epub 2016 Dec 8.
• The prothrombotic risk in multiple myeloma (MM) could be potentially assessed by thrombin generation (TG) assays. TG was performed using Calibrated Automated Thrombography with 5 and 1 pM tissue factor. We compared baseline TG among 24 MM patients, 19 MGUS, and 50 healthy controls, and assessed
• PMID 27931131

• JAK2V617F and calreticulin mutations in recurrent venous thromboembolism: results from the EDITH prospective cohort.

• Ianotto JC1,2, Chauveau A3,4, Mottier D5,6, Ugo V7, Berthou C8, Lippert E3,4, Delluc A5,6.
• Annals of hematology.Ann Hematol.2017 Mar;96(3):383-386. doi: 10.1007/s00277-016-2853-1. Epub 2016 Oct 20.
• Cancer incidence in patients with recurrent unprovoked venous thromboembolism (VTE) is much higher than after a first event, but the incidence of myeloproliferative neoplasms (MPN) in this situation is still unknown. We tested for JAK2V617F and calreticulin mutants, 372 DNA samples of patients treat
• PMID 27766390

Japanese Journal

• 症例 先天性血栓性素因を有し術後6日目に肺血栓塞栓症を発症した若年性卵巣癌の1例

• 産科と婦人科 84(3), 358-362, 2017-03
• NAID 40021107616

• Aln Retrievable Vena Cava Filter - Efficacy, Safety and Retrievability -

• 弘前医学 67(2-4), 158-165, 2017-02-27
• NAID 120005982571

• 症例 経皮的心肺補助の使用により重度障害なく救命しえた大腿骨骨折後肺動脈血栓塞栓症の1例

• 整形・災害外科 60(2), 225-228, 2017-02
• NAID 40021093800

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