Deep vein thrombosis is an abnormal clotting of blood in the deep veins, which occurs in the lower extremities. It is a relatively common disease in Europe and the United States, and the trend is increasing year by year in China. When the disease is not diagnosed and treated in time in the acute stage, some clots may be dislodged and cause embolism of the patient’s pulmonary vessels and lead to death. Other patients are not spared from the sequelae of chronic thrombosis, which causes long-term illness and affects life and work ability.
The high-risk factors are as follows.
1. Age.
Deep vein thrombosis (DVT) can be seen in people of any age, but statistics show that the incidence increases gradually with age, and the incidence of 80-year-old people is more than 30 times that of 30-year-old people. The effect of age on the development of DVT is multifaceted, with increasing age increasing the susceptibility to DVT. Experiments have shown that the coagulation factor activity in the blood of the elderly is higher and the pumping effect of calf muscles is weakened so that the blood is more stagnant in the floundering plexus and venous valve pocket, so the incidence of DVT is higher than that of young people.
2, braking.
Clinically, it is often seen that patients who are bedridden for a long time are prone to DVT. Autopsy found that the incidence of DVT in patients who are bedridden for 0-7 days is 15%, while in those who are bedridden for 2-12 weeks, the incidence of DVT is 79%-94%. In stroke patients, the incidence of DVT was 53% in those with lower limb paralysis and only 7% in those without lower limb paralysis. The incidence of DVT is also higher in people who travel long distances by car or airplane. The pumping action of calf muscles plays an important role in lower limb venous return, and venous blood return slows down significantly after braking, thus increasing the risk of DVT development.
3. History of venous thrombosis.
23% to 26% of patients with acute DVT have a previous history of venous thrombosis, and these newly formed thrombi often come from the original diseased veins. Studies have found that recurrent DVT patients often have hypercoagulable blood.
4, malignant tumors.
Statistics found that 19%-30% of DVT patients combined with malignant tumors, lung cancer is the most likely to cause DVT a malignant tumor, other malignant tumors such as genitourinary system and gastrointestinal system also easy to complicate DVT. sometimes, DVT can be used as a messenger of malignant tumors, when DVT occurs without obvious causes, should be alert to possible malignant tumors. The causes of DVT caused by malignant tumors are many, among which the main reason is that malignant tumors release procoagulant substances and increase the activity of blood clotting factors. The concentration of fibrinogen and platelet count in the blood of tumor patients are often higher than normal, while the concentration of anticoagulant substances such as antithrombin, C protein and S protein are lower than normal. In addition, surgical treatment of tumors and chemotherapy are also important factors leading to DVT. The incidence of DVT is significantly higher in chemotherapy patients with breast cancer, lymphoma and plasma cell disease, which may be related to the toxic effects of chemotherapy drugs on vascular endothelial cells, induction of hypercoagulable state, inhibition of fibrinolytic activity, tumor cell necrosis and intravenous cannulation.
5. Surgery.
The high incidence of post-surgical day VT shows that surgery is an important susceptibility factor for DVT, and the patient’s age, type of surgery, trauma size, surgery time and post-operative bed rest time all affect the occurrence of DVT. The type of surgery is particularly important, with the incidence of DVT after general surgery at around 19%, neurosurgery at around 24%, and femur fracture, hip arthroplasty, and knee arthroplasty at 48%, 51%, and 61%, respectively. Intraoperative nuclear scans have been able to detect 125I-labeled fibrinogen deposits in the lower extremities in about half of the patients, and in the rest, fibrinogen deposits can be detected 3 to 5 days after surgery, but this does not indicate that DVT occurs immediately after surgery. Some statistics show that DVT occurs in 25% of patients after abdominal surgery within 6 weeks after discharge from the hospital. causes of DVT triggered by surgery include perioperative braking, intraoperative and postoperative abnormalities of coagulation, anticoagulation and thrombolytic system in vivo, and venous vascular injury.
6. Trauma.
Autopsy of traumatic death found that 62% to 65% of the deceased had DVT. Trauma may lead to lower limb fracture, spinal cord injury, venous vascular injury and the need for surgical treatment, etc., making trauma patients prone to DVT. In addition, the blood is in a hypercoagulable state after trauma, which also promotes thrombosis.
7.Primary blood hypercoagulation state.
Common in patients with genetic mutation or hereditary anticoagulant defect, 5%-10% of all DVT patients are caused by primary blood hypercoagulation. The normal human anticoagulation system includes antithrombin, C protein system, tissue factor pathway (exogenous coagulation pathway) inhibitory factors, etc. Antithrombin can inhibit factors Xa, Ⅸa, Ⅺa and Ⅻa, and heparin and heparin-like mucopolysaccharide on the surface of vascular endothelial cells can promote their anticoagulant effects. The C protein and S protein systems bind thrombin and thrombomodulin on the surface of endothelial cells and inhibit factor V and factor VIII activity. Genetic defects lead to anticoagulant deficiency, leaving the blood in a hypercoagulable state. Primary anticoagulant deficiency occurs in about 0.5% of the population and includes both pure and heterozygous gene defects. The incidence of thrombosis is much higher in pure heterozygotes than in heterozygotes. The first occurrence of DVT in primary hypercoagulable blood is often before the age of 45, often induced under certain circumstances (such as surgery, trauma, etc.), and the thrombus is prone to recurrence, the site of the thrombus is often atypical, clinically often seen mesenteric vein thrombosis, intracranial venous sinus thrombosis, etc.
8.Postpartum.
The incidence of postpartum DVT is high, while DVT patients in domestic pregnancy are less common. The occurrence of postpartum DVT is closely related to the blood being in a hypercoagulable state. Placental abruption in the uterus after delivery can quickly stop bleeding in a short period of time, without causing postpartum hemorrhage, in addition to the contraction of the uterus itself, and blood is directly related to the hypercoagulable state. The placenta produces a large amount of estrogen during pregnancy, reaching its peak at term, and the amount of estriol in the body can increase to 1000 times that of non-pregnancy, and estrogen promotes the production of various coagulation factors by the liver, while a large increase in fibrinogen in the body at the end of pregnancy aggravates the hypercoagulable state, which may lead to DVT.
9. Oral contraceptives.
As early as the 1960s, it was reported that oral contraceptives are prone to DVT, and it has been found that 1/4 of women of childbearing age suffering from DVT are related to taking contraceptives, and the survey also found that the pulmonary embolism caused by DVT is significantly reduced after women of childbearing age stop using contraceptives. The reason why contraceptives are prone to DVT may be related to the variation of coagulation factor V, which reduces the anticoagulant effect of C protein. The higher the dose of estrogen in contraceptives, the more likely it is to cause DVT, and contraceptives at doses >50 μg have a greater risk of thrombus formation relative to those at doses <50 μg. Third-generation contraceptives are more likely to cause DVT than second-generation contraceptives because the progestins in third-generation contraceptives are mainly deoxyprogesterone, oxynolone, or gestodienone, which are also prone to thrombosis. Surveys have shown that women of childbearing age taking third-generation contraceptives are eight times more likely to have DVT than those not using the pill.
Estrogens are also used to treat prostate enlargement in men and menopausal syndrome in women, as well as lactation in breastfeeding women. The incidence of DVT is also higher in these individuals. Estrogen has the effect of increasing blood viscosity, raising the concentration of blood fibrinogen, plasma coagulation factor VII and X, and increasing the adhesion and aggregation of platelets, thus making it easy to form blood clots.
10.Blood type.
Blood type and DVT have been found to have a certain relationship, people with A blood type are most likely to suffer from DVT, and relatively speaking, O blood type has the least risk of DVT. The reason for this is not completely clear, now found that different blood types of people with different vascular endothelial cell surface of certain structures, O blood type endothelial cell surface of von Willebrand factor significantly reduced.
11. Ethnicity.
The incidence of DVT in Europe is much higher than in Asia, although racial differences may lead to differences in the coagulation and anticoagulation system of the body, but the difference in living habits and dietary structure may also affect the occurrence of DVT, and the survey found that the incidence of DVT in black Americans is higher than in black Africans of the same race.
12. Central venous cannulation.
More and more central venous cannulas are being inserted clinically, which makes the incidence of DVT increase accordingly, especially in the upper extremity DVT, 65% of the patients are related to central venous cannulas. Venous cannulation not only damages the vessel wall, but also tends to form thrombus on the surface of the cannula. The type of catheter has a significant impact on the occurrence of DVT, with polytetrafluoroethylene (PTFE) catheters or catheters coated with heparin having a lower chance of DVT than other catheters. The caliber of the catheter, the number of venipunctures, the time of placement and the drugs instilled can affect the occurrence of DVT.
13, Enterocolitis.
Patients with enterocolitis combined with pulmonary embolism are often reported clinically. The cause of DVT caused by enterocolitis is not clear, except that the platelet count, coagulation factor V and VIII content and fibrinogen concentration in the blood of these patients were found to be significantly elevated. The site of DVT caused by enterocolitis is often atypical, such as intracranial venous sinus thrombosis.
14. Systemic lupus erythematosus.
Patients with SLE are often combined with arteriovenous thrombosis, recurrent miscarriages, thrombocytopenia and neurological disorders. This may be related to higher lupus antithrombin antibodies and anti-cardiolipin antibodies in the body during the active phase. Similar conditions have been found in some other autoimmune patients. It was found that patients with SLE with high levels of antithrombin antibodies had six times the chance of venous-derived pulmonary embolism compared to controls, while those with higher anti-cardiac phospholipid antibodies had two times the chance of controls.
15, Other.
Whether obesity, varicose veins of the lower extremities and cardiac insufficiency are susceptibility factors of DVT is still debated, and multi-factor statistical analysis concluded that obesity, varicose veins of the lower extremities and cardiac insufficiency are not independent susceptibility factors, and that the susceptibility of these patients to DVT may be related to the concomitant other susceptibility factors.
Among the above 15 susceptibility factors, most of them are the change of blood composition into hypercoagulable state leading to the formation of DVT in the lower extremities, therefore, the change of blood composition into hypercoagulable state is the determining factor of DVT formation. Pulmonary embolism is caused by the dislodgement of thrombus in the lower extremities. The severity of pulmonary embolism varies, and the symptoms can be asymptomatic or sudden and fatal, and most of them cause different degrees of respiratory distress. So when you encounter the above situation, pay attention to prevention and avoid the occurrence of venous thrombosis of lower limbs.