Deep venous thrombosis is a condition where there is a blood clot in a deep vein (a vein that accompanies an artery).
Causes, incidence, and risk factors of thrombosis
Deep venous thrombosis (DVT) affects mainly the veins in the lower leg and the thigh. It involves the formation of a clot (thrombus) in the larger veins of the area. This clot may interfere with circulation, and it may break off and travel through the blood stream (embolize). A resulting embolus can lodge in the brain, lungs, heart, or other area, causing severe damage to that organ.
Risks include prolonged sitting, bedrest, or immobilization (such as on long plane or car trips), recent surgery or trauma (especially hip, knee or gynecological surgery), fractures, childbirth within the last 6 months and the use of medications such as estrogen and birth control pills. Risks also include a history of
polycythemia vera, malignant (cancerous), and inherited or acquired hypercoagulability (a condition where the blood is more likely to clot).
Deep venous thrombosis is most common in adults over age 60 but can occur in any age group.
Symptoms of thrombosis
- leg pain in one leg only
- leg tenderness in one leg only
- swelling (edema) of only one leg
- increased warmth of one leg
- changes in skin color of one leg, redness
Signs and tests of thrombosis
An examination may reveal a red, swollen, or tender leg.
The presence of deep venous thrombosis may be seen on:
Many of the inherited and acquired causes of hypercoagulability (clotting tendency) can be detected by blood tests:
- venography of the legs
- Doppler ultrasound exam of an extremity
- plethysmography of the legs
- D-dimer blood test
- antithrombin III, protein C, protein S
- Factor V Leyden
- Prothrombin 20210a mutation
- DIC screening
- lupus anticoagulant and anticardiolipin antibodies
Treatment of thrombosis
Treatment of thrombosis is intended to prevent the development of a pulmonary embolus and to prevent other thrombosis.
For years, the standard treatment has been an anticoagulant medication called heparin, which was given through the vein. This results in very quick anticoagulation and treatment of the clot. Along with heparin an oral medication called warfarin is given.
Warfarin usually takes several days to become fully effective, so heparin is continued until the warfarin has been fully effective for at least 24 hours. The warfarin is usually continued for about 6 months. In almost all circumstances, warfarin is started only after heparin has been started.
Because heparin is given as a continuous intravenous (I.V.) infusion, it requires hospitalization. However, newer forms of heparin, known as low molecular-weight heparin (usually a drug called enoxaparin) can be used in some circumstances. This heparin can be given by injection once or twice a day and thus can shorten or eliminate the need for hospitalization.
Warfarin causes an increase in the time it takes blood to clot (known as the PT). The PT is monitored to determine if the blood is sufficiently anticoagulated. A measurement known as the INR standardizes PT measurements between labs. For most patients warfarin is adjusted to keep the INR between 2 and 3.
Most thrombosis disappears without difficulty, however there is a risk of recurrence. Some patients may develop some chronic pain and swelling in the leg known as post phlebitic syndrome. Pulmonary embolus is uncommon when thrombosis is treated properly but can occur and can be life threatening.
- pulmonary embolus
- post-phlebitic syndrome
Calling your health care provider
Call your health care provider if symptoms suggestive of thrombosis occur.
Go to the emergency room or call the local emergency number (such as 911) if chest pain, difficulty breathing, fainting, loss of consciousness, or other severe symptoms occur in a person with thrombosis.
Prevention of thrombosis
Anticoagulants may be prescribed as a preventive measure for high risk people or people undergoing high risk surgical procedures. Minimize immobility of the legs (ambulate frequently during long plane trips, car trips, etc).