Venous thrombosis
Encyclopedia
A venous thrombosis is a blood clot that forms within a vein
. (Thrombosis
is a medical term for blood clotting (Haemostasis) occurring in the wrong place, i.e. a thrombus forming on the inside wall of a blood vessel.
Since the veins return blood
to the heart
, if a piece of a blood clot formed in a vein breaks off it can be transported to the right side of the heart, and from there into the lung
s. A piece of thrombus that is transported in this way is an embolism
: the process of forming a thrombus that becomes embolic is called a thromboembolism. An embolism that lodges in the lungs is a pulmonary embolism
(PE). A pulmonary embolus is a very serious condition that can be fatal if not recognized and treated promptly.
Systemic embolisms of venous origin can occur in patients with an atrial
or ventricular septal defect
, through which an embolus may pass into the arterial system. Such an event is termed a paradoxical embolism
.
in medical patients must be individualized as routine prophylaxis does not appear to decrease mortality and while it does decrease the risk of pulmonary embolism
increases the risk of bleeding. Mechanical measures also appeared of little benefit in this group. Recommendations in surgical patients include mechanical thromboprophylaxis methods and devices such as frequent ambulation, intermittent pneumatic compression
as well as blood thinners.
, fondaparinux
and more recently dabigatran
has shown promise. Vitamin K antagonist
s such as warfarin
are also commonly used.
Vein
In the circulatory system, veins are blood vessels that carry blood towards the heart. Most veins carry deoxygenated blood from the tissues back to the heart; exceptions are the pulmonary and umbilical veins, both of which carry oxygenated blood to the heart...
. (Thrombosis
Thrombosis
Thrombosis is the formation of a blood clot inside a blood vessel, obstructing the flow of blood through the circulatory system. When a blood vessel is injured, the body uses platelets and fibrin to form a blood clot to prevent blood loss...
is a medical term for blood clotting (Haemostasis) occurring in the wrong place, i.e. a thrombus forming on the inside wall of a blood vessel.
Classification
Superficial venous thromboses can cause discomfort but generally do not cause serious consequences, unlike the deep venous thromboses (DVTs) that form in the deep veins of the legs or in the pelvic veins.Since the veins return blood
Blood
Blood is a specialized bodily fluid in animals that delivers necessary substances such as nutrients and oxygen to the cells and transports metabolic waste products away from those same cells....
to the heart
Heart
The heart is a myogenic muscular organ found in all animals with a circulatory system , that is responsible for pumping blood throughout the blood vessels by repeated, rhythmic contractions...
, if a piece of a blood clot formed in a vein breaks off it can be transported to the right side of the heart, and from there into the lung
Lung
The lung is the essential respiration organ in many air-breathing animals, including most tetrapods, a few fish and a few snails. In mammals and the more complex life forms, the two lungs are located near the backbone on either side of the heart...
s. A piece of thrombus that is transported in this way is an embolism
Embolism
In medicine, an embolism is the event of lodging of an embolus into a narrow capillary vessel of an arterial bed which causes a blockage in a distant part of the body.Embolization is...
: the process of forming a thrombus that becomes embolic is called a thromboembolism. An embolism that lodges in the lungs is a pulmonary embolism
Pulmonary embolism
Pulmonary embolism is a blockage of the main artery of the lung or one of its branches by a substance that has travelled from elsewhere in the body through the bloodstream . Usually this is due to embolism of a thrombus from the deep veins in the legs, a process termed venous thromboembolism...
(PE). A pulmonary embolus is a very serious condition that can be fatal if not recognized and treated promptly.
Systemic embolisms of venous origin can occur in patients with an atrial
Atrial septal defect
Atrial septal defect is a form of congenital heart defect that enables blood flow between the left and right atria via the interatrial septum. The interatrial septum is the tissue that divides the right and left atria...
or ventricular septal defect
Ventricular septal defect
A ventricular septal defect is a defect in the ventricular septum, the wall dividing the left and right ventricles of the heart.The ventricular septum consists of an inferior muscular and superior membranous portion and is extensively innervated with conducting cardiomyocytes.The membranous...
, through which an embolus may pass into the arterial system. Such an event is termed a paradoxical embolism
Paradoxical embolism
A paradoxical embolism is a kind of stroke or other form of arterial thrombosis caused by embolism of a thrombus of venous origin through a lateral opening in the heart, such as a patent foramen ovale....
.
Risk factors
- General
- Older age
- Female sex
- Smoking
- Obesity
- Dehydration
- Pregnancy
- Immobilization
- Minor injuries
- Height, in men
- Medical
- SurgerySurgerySurgery is an ancient medical specialty that uses operative manual and instrumental techniques on a patient to investigate and/or treat a pathological condition such as disease or injury, or to help improve bodily function or appearance.An act of performing surgery may be called a surgical...
- TraumaPhysical traumaTrauma refers to "a body wound or shock produced by sudden physical injury, as from violence or accident." It can also be described as "a physical wound or injury, such as a fracture or blow." Major trauma can result in secondary complications such as circulatory shock, respiratory failure and death...
- Use of combined (containing both estrogen and progestin) forms of hormonal contraceptionHormonal contraceptionHormonal contraception refers to birth control methods that act on the endocrine system. Almost all methods are composed of steroid hormones, although in India one selective estrogen receptor modulator is marketed as a contraceptive. The original hormonal method—the combined oral contraceptive...
- Varicose veinsVaricose veinsVaricose veins are veins that have become enlarged and tortuous. The term commonly refers to the veins on the leg, although varicose veins can occur elsewhere. Veins have leaflet valves to prevent blood from flowing backwards . Leg muscles pump the veins to return blood to the heart, against the...
- Malignancy
- Kidney disorders
- Lupus anticoagulantLupus anticoagulantLupus anticoagulant is an immunoglobulin that binds to phospholipids and proteins associated with the cell membrane. It is important to note that this disease name is actually a misnomer...
- Paroxysmal nocturnal hemoglobinuriaParoxysmal nocturnal hemoglobinuriaParoxysmal nocturnal hemoglobinuria , sometimes referred to as Marchiafava-Micheli syndrome, is a rare, acquired, potentially life-threatening disease of the blood characterised by complement-induced intravascular hemolytic anemia , red urine and thrombosis...
- Inflammatory bowel diseaseInflammatory bowel diseaseIn medicine, inflammatory bowel disease is a group of inflammatory conditions of the colon and small intestine. The major types of IBD are Crohn's disease and ulcerative colitis.-Classification:...
- Thromboangiitis obliterans (Mb Bürger)
- Disseminated intravascular coagulationDisseminated intravascular coagulationDisseminated intravascular coagulation , also known as disseminated intravascular coagulopathy or consumptive coagulopathy, is a pathological activation of coagulation mechanisms that happens in response to a variety of diseases. DIC leads to the formation of small blood clots inside the blood...
- Surgery
- Familial
- Antithrombin III deficiencyAntithrombinAntithrombin is a small protein molecule that inactivates several enzymes of the coagulation system. Antithrombin is a glycoprotein produced by the liver and consists of 432 amino acids. It contains three disulfide bonds and a total of four possible glycosylation sites...
- Protein C deficiencyProtein C deficiencyProtein C deficiency is a rare genetic trait that predisposes to thrombotic disease. It was first described in 1981. The disease belongs to a group of genetic disorders known as thrombophilias. The prevalence of protein C deficiency has been estimated to about 0.2% to 0.5% of the general population...
/Protein S deficiencyProtein S deficiencyProtein S deficiency is a disorder associated with increased risk of venous thrombosis. Protein S, a vitamin K-dependent physiological anticoagulant, acts as a nonenzymatic cofactor to activated protein C in the proteolytic degradation of factor Va and factor VIIIa... - APC resistance (Factor V LeidenFactor V LeidenFactor V Leiden is the name given to a variant of human factor V that causes a hypercoagulability disorder. In this disorder the Leiden variant of factor V cannot be inactivated by activated protein C. Factor V Leiden is the most common hereditary hypercoagulability disorder amongst Eurasians...
) - Dysfibrogenemia
- Hypoplasminogenemia
- Familial hyperhomocysteinemiaHyperhomocysteinemiaHyperhomocysteinemia or hyperhomocysteinaemia is a medical condition characterized by an abnormally large level of homocysteine in the blood....
- Antithrombin III deficiency
Prevention
Prophylaxis of venous thromboembolism with heparinHeparin
Heparin , also known as unfractionated heparin, a highly sulfated glycosaminoglycan, is widely used as an injectable anticoagulant, and has the highest negative charge density of any known biological molecule...
in medical patients must be individualized as routine prophylaxis does not appear to decrease mortality and while it does decrease the risk of pulmonary embolism
Pulmonary embolism
Pulmonary embolism is a blockage of the main artery of the lung or one of its branches by a substance that has travelled from elsewhere in the body through the bloodstream . Usually this is due to embolism of a thrombus from the deep veins in the legs, a process termed venous thromboembolism...
increases the risk of bleeding. Mechanical measures also appeared of little benefit in this group. Recommendations in surgical patients include mechanical thromboprophylaxis methods and devices such as frequent ambulation, intermittent pneumatic compression
Intermittent pneumatic compression
A therapeutic technique used in medical devices that include an air pump and inflatable auxiliary sleeves, gloves or boots in a system designed to improve venous circulation in the limbs of patients who suffer edema or the risk of deep vein thrombosis ....
as well as blood thinners.
Treatment
Evidence-based guidelines have been published for the treatment of venous thromboembolism. Medications used to treat this condition include anticoagulants such as heparinHeparin
Heparin , also known as unfractionated heparin, a highly sulfated glycosaminoglycan, is widely used as an injectable anticoagulant, and has the highest negative charge density of any known biological molecule...
, fondaparinux
Fondaparinux
Fondaparinux is an anticoagulant medication chemically related to low molecular weight heparins. It is marketed by GlaxoSmithKline.-Structure and mechanism:Fondaparinux is a synthetic pentasaccharide Factor Xa inhibitor...
and more recently dabigatran
Dabigatran
Dabigatran is an oral anticoagulant from the class of the direct thrombin inhibitors...
has shown promise. Vitamin K antagonist
Vitamin K antagonist
Vitamin K antagonists are a class of anticoagulants. They reduce blood clotting by inhibiting the recycling of vitamin K epoxide back to the active reduced form of vitamin K. The term Vitamin K antagonists is a misnomer. These drugs do NOT antagonize the action of Vitamin K...
s such as warfarin
Warfarin
Warfarin is an anticoagulant. It is most likely to be the drug popularly referred to as a "blood thinner," yet this is a misnomer, since it does not affect the thickness or viscosity of blood...
are also commonly used.
See also
- Portal vein thrombosisPortal vein thrombosisPortal vein thrombosis is a form of venous thrombosis affecting the hepatic portal vein, which can lead to portal hypertension and reduction in the blood supply to the liver.-Causes:...
- Deep vein thrombosisDeep vein thrombosisDeep vein thrombosis is the formation of a blood clot in a deep vein. Deep vein thrombosis commonly affects the leg veins or the deep veins of the pelvis. Occasionally the veins of the arm are affected...
- Pulmonary embolismPulmonary embolismPulmonary embolism is a blockage of the main artery of the lung or one of its branches by a substance that has travelled from elsewhere in the body through the bloodstream . Usually this is due to embolism of a thrombus from the deep veins in the legs, a process termed venous thromboembolism...
- Arterial thrombosis