Deep Vein Thrombosis (DVT) - Risk, Symptoms and Treatment

Thrombosis is a medical term indicating the formation of a blood clot within a blood vessel, causing severe limitation or interruption of blood flow therein. Thrombosis may occur in arteries and is called arterial thrombosis, or in the veins, which is called venous thrombosis.

Deep vein thrombosis
Deep vein thrombosis

The most common form of venous thrombosis is deep vein thrombosis (DVT), which occurs in the leg veins, legs or pelvis, clinically characterized by a swelling above and pain in the affected limb.

In this article we will explain what is deep vein thrombosis, which are their causes, risk factors, symptoms, complications, and what are the strategies for treatment and prevention.

What is thrombosis

Clot formation is a complex defense mechanism that prevents the patient to bleed indefinitely every time one of your blood vessels suffer an injury. The coagulation system is responsible for maintaining the blood in its liquid form, but it is highly effective to induce solidification where the wall of a vein or artery suffer some injury. Immediately following a vessel undergoing injury, the coagulation system starts to act to create a clot which act as buffer to stop the leakage of blood out of the bloodstream.

In the vast majority of cases, the clot formation is made without equivocation, limited only to the wall of the injured vessel and tissues where the blood spilled without interfering materially in blood flow within the vessel. In healthy people, there is a fine balance between the factors that prevent clotting and factors that encourage clot formation, so that the patient does not form clots spontaneously or run the risk of bleeding with minimal day-to-day traumas.

Thrombosis is an undesirable event clotting system because it creates large clots within the blood vessel, causing obstruction of blood flow in this region.

The venous and arterial thrombosis clinically manifest differently, since veins and arteries have distinct functions in the body. The arteries are the vessels responsible for carrying oxygen-rich blood and nutrients to the tissues, while veins are the vessels that do the opposite direction, oozing blood already used by the tissues back to the heart and lungs for him to be re oxygenated.

Therefore, if thrombosis occurs within an artery, it prevents the blood reaches the tissues and organs fed by that artery, causing ischemia and infartes. The best known cases of arterial thrombosis are acute myocardial infarction and stroke.

When the thrombosis occurs within a vein, it obstructs the flow of blood, causing the same to be dammed in that region. The most common form of venous thrombosis is thrombosis of the lower limbs, affecting the deep and caliber veins of the leg, thigh or pelvis. In this case, usually the blood reaches the affected lower limb, but can not return because, as one of thrombosed veins is one of the main, if not the principal flow path is obstructed. The blood to return, must find one or more side paths, which are usually smaller caliber veins, disabled, the short term to achieve adequate flow around the flow of blood.

How appears venous thrombosis

In normal situations, the blood must always remain in liquid form, flowing freely through the bloodstream. The formation of a blood clot (thrombus) inside a vein is an unnatural event, which occurs mainly due to three factors known as Virchow's triad:

1. Reduction of blood flow in the vessel - balance between factors which promote the clotting and coagulation factors preventing disappears when blood flow becomes slower. Blood stasis is a situation that stimulates the action of clotting factors, increasing the risk of the appearance of a thrombus.

2. lesion of the blood vessel wall - every time the wall of a blood vessel receives an injury, the coagulation system is activated for formation of a buffer clot to prevent blood loss out of the vessel. Depending on the degree and location of the injury, the formation of a big thrombus can occur.

3. Changes in blood components - if the patient has a disease that alters materially blood components, especially the factors that favor or prevent clotting, the necessary balance of the coagulation system disappears, increasing the risk of thrombus appearance within the vessels.

In general, where the patient has a stroke, one or more of the three factors described above are present in their genesis. A variety of diseases and conditions may predispose a patient to thrombosis, as discussed below.

Risk factors for thrombosis

Several factors may increase the risk of thrombosis development, especially of the lower limbs. The most important are thrombophilia, blood disorders that cause the coagulation system becomes unregulated, creating a hypercoagulable state and high risk for thrombus formation. Among the most common thrombophilia, we can highlight:
  • Mutation Factor V Leiden.
  • Mutation of the prothrombin gene gene.
  • Protein deficiency S.
  • Protein deficiency C.
  • Deficiency of antithrombin.
  • Dysfibrinogenemia.
  • Anti-phospholipid antibody.

Fortunately, despite being a very strong risk factor for thrombosis, the thrombophilia are uncommon diseases. Most cases of thrombosis are caused by other factors. Let's talk briefly about the most important.

1) Surgery

Patients undergoing surgical procedures, especially surgery in the pelvic area and lower limbs at high risk of thrombus formation in the lower limbs. The effect of anesthetics, the proper handling of blood vessels and underlying tissues during surgery and prolonged time without getting up postoperative make the surgery an event at high risk of deep vein thrombosis.

When we walk, the foot strikes the ground and the contraction of muscles, especially calf, help push blood in the veins of the legs up toward the heart. Get much time lying down, especially for those with venous insufficiency, promotes stasis of blood in the lower limbs.

2) Traumas

For reasons similar to those of surgery, major trauma are also important risk factors for deep vein thrombosis, not only the impact on blood vessels, but also by the time the patient is immobilized in bed after the accident.

3) Long sitting travel (economy class syndrome)

Long airplane trips, usually over 8 hours may facilitate the onset of deep vein thrombosis, particularly in people with other risk factors such as obesity, varicose veins, smoking, pregnancy, etc. Have you noticed how your feet are swollen and the shoe is more difficult to put on after a long plane trip? The fact of sitting for long hours with bent legs, hinders the return of venous blood to the heart by promoting stasis and therefore thrombus formation.

4) Cancer

Some malignant tumors produces substances which increase the coagulability of the blood, favoring the formation of thrombi.

5) Heart failure

Patients with heart failure have a weak heart, hard to pump blood through the body. This leads to stagnation of blood in the lower limbs and promotes clot formation.

6) Pregnancy

Hormonal changes increase the clotting ability of pregnant. Furthermore, as the uterus grows, the vena cava will be compressed, which makes the flow of blood from the veins of the lower limbs. Pregnant women have 5 times more likely to develop blood clots than non-pregnant women of the same age.

Besides the already described, there are several other risk factors for deep vein thrombosis, among which it is worth quoting:
  • Obesity
  • Smoking
  • Use of hormonal contraceptives
  • Age over 60 years
  • Nephrotic syndrome
  • Use of certain medications, such as tamoxifen, erythropoietin, thalidomide and hormone replacement in menopause
  • Family history of thrombosis
  • Polycythemia vera
  • Essential thrombocytopenia
  • inflammatory bowel disease
  • Central venous catheter use in the femoral vein

Symptoms of deep vein thrombosis

Symptoms of DVT depend on the size of the thrombus and the degree of obstruction of the affected vein. As these are the deep veins, away from the skin, the patient is perfectly possible to have a stroke and have no symptoms.

When the thrombus is large enough to threaten the flow of blood in the vein, the main symptoms are swelling, pain, temperature increase and redness of the affected limb. A leg that suddenly starts to hurt and becomes more swollen than the other is a sign that should always raise the suspicion of thrombosis.

The diagnosis of DVT is usually done with ultrasound Doppler of the veins of the lower limbs. Other tests, such as magnetic resonance angiography or CT angiography can also be used.

Risks of deep vein thrombosis

The great danger of DVT is the risk of a piece of thrombus break loose and travel through the bloodstream to one of the lungs, causing a frame called pulmonary embolism (PE). Small thrombi cause located pulmonary infarction, clinically manifested as chest pain, sudden shortness of breath.

Depending on the size of the piston (piece of thrombus that is released), the same can block large pulmonary vessels such as the pulmonary artery, preventing blood reaches of the lungs. In this case, the heart may collapse as it tries to pump blood into the lungs, but can not due to the large obstruction ahead. The patient with massive thromboembolism often rapidly progress to cardiac arrest and death.

The DVT occurring in the veins of the uppermost limb, such as the popliteal, iliac and femoral veins are those which have greater risk of releasing emboli. Thromboses occurring in the veins below the knee are less dangerous because they present less risk of TEP.

Treatment of deep vein thrombosis

Treatment of DVT aims to: reduce the risk of embolization to the lungs, preventing the growth of the thrombus and prevent the formation of new thrombi.

If untreated, about 1 every 2 patients with DVT in the uppermost veins of the leg will show pulmonary embolism. This means that if untreated, DVT is a picture with unacceptable risk of death.

Anticoagulation blood with unfractionated heparin or low molecular weight heparin is effective in reducing the risk of TEP and the formation of new thrombi. After 5 days of heparin, which is administered by subcutaneous injection, the patient is taking anticoagulants only in tablet, such as warfarin. Warfarin is maintained for 3 to 6 months depending on the severity and risk factors of the patient.

Patients with DVT should remain in absolute rest in bed during the early days of anticoagulation, for the mobilization of the affected limb increases the risk of embolization.

In patients with contraindication to anticoagulation or that despite anticoagulation, continue to present new episodes of thromboembolism, indicates the implementation of a filter in the vena cava. The vena cava filter is a kind of network that is located within the vena cava, the abdominal region, and prevents pistons from the lower members may reach the lungs.

Prevention of deep vein thrombosis

The prevention of DVT is essential in patients with high risk, particularly those with thrombophilia or who have recently undergone surgery. In thrombophilia, prevention should be done with the use of anticoagulants for the rest of life. In cases of patients undergoing surgery is indicated, in the immediate postoperative period, the use of compression stockings and low doses of heparin, if the patient needs to stay in bed. Ideally, all newly operated patient get up and walk as soon as possible. The simple fact that the patient can take a few steps throughout the day already greatly reduces the risk of DVT.

In the long plane trips, it is stated that the person get up every two hours and take a walk by the aircraft. Avoid alcohol and stay well hydrated is also important.
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