Deep Venous Thrombosis

Deep venous thrombosis, also called DVT, refers to a blood clot that has formed in one of the large veins far below the skin.

What is going on in the body?

A deep venous thrombosis is most common in the legs, but it can occur in other parts of the body. A blood clot in a vein blocks the normal flow of blood back to the heart. It also causes the affected vein to become inflamed.

What are the causes and risks of the condition?

A deep venous thrombosis forms when a blood clot in a vein blocks the normal flow of blood back to the heart. Circumstances that increase an individual's risk of developing DVT include:

Diseases and conditions that increase a person's risk for DVT include:

Medicines that can increase the risk for DVT include:

Injuries can also increase a person's risk for DVT. Common injuries linked to DVT include:

Recently, there have been conflicting research reports about the role of long airplane flights in deep venous thrombosis. Some studies showed a relationship between airline travel and an increase in the blood's tendency to form clots. The researchers attributed the increased risk of clot formation to the low pressure, low oxygen, dehydration, and lack of activity on long flights. Another study showed that individuals hospitalized with DVT were four times more likely to have gone on a long trip recently than those treated at the hospital for other conditions. Because of findings like this, deep venous thrombosis is often referred to as "economy class syndrome."

However, other researchers have not found the same relationship. Some suggest that only people with a particular genetic abnormality are at risk for economy class syndrome. More research is needed in this area.

What are the signs and symptoms of the condition?

Following are some of the symptoms of a deep venous thrombosis:

How is the condition diagnosed?

The first step in diagnosing a deep venous thrombosis is a medical history and physical examination. Blood flow studies, a type of ultrasound, are commonly used to diagnose DVT. The healthcare provider may also order an MRI or other imaging studies.

What can be done to prevent the condition?

DVT cannot always be prevented. Some helpful measures include:

Although the research is still inconclusive about the effects of airplane trips and other forms of travel on DVT, people can lower their risk of DVT by taking these steps:

Blood-thinning medicines can help prevent DVT. These include heparin, enoxaparin, and warfarin. Compression stockings can also be used to improve the flow of blood through the veins back up to the heart.

A recent large-scale study in Canada looked at DVT in individuals 65 years or older. The study found that statins, which are medicines used to lower cholesterol, decreased the risk of DVT by 22% in this group. While further study is recommended, the findings are encouraging.

What are the long-term effects of the condition?

Most patients will recover from an episode of deep venous thrombosis without long-term problems. People who have had DVT have a higher risk of getting it again. The most serious risk of DVT is a pulmonary embolus. This is a piece of the blood clot that breaks off and travels to the lung. A blood clot in the lung can cause death.

DVT may also cause chronic pain and swelling of the affected leg. There are rare cases of a stroke resulting from a DVT.

What are the risks to others?

A deep venous thrombosis is not contagious and poses no risk to others.

What are the treatments for the condition?

Treatment of a deep venous thrombosis focuses on preventing a pulmonary embolus. Bed rest and elevating the leg can help reduce the swelling and pain. The person is often given an injection of a blood-thinning medicine. The injection may be given through an IV or under the skin. These blood-thinning medicines, such as heparin and enoxaparin, help prevent further growth of the blood clot. After a few days of blood-thinning medicines by injection, the person can be switched to pills. Warfarin is the most common blood-thinning pill.

In some people, blood-thinning medicines cannot be used. For example, a person may have a high risk of bleeding, a side effect of thinning the blood. In these cases, a surgical procedure can be done. This involves inserting a filter in one of the major veins of the body that leads to the heart. This filter catches any clots that break off so they cannot get into the lungs and cause death.

What are the side effects of the treatments?

Heparin can cause bleeding and lower blood platelet counts, called thrombocytopenia. Warfarin can also cause bleeding, which in rare cases is fatal. Warfarin interferes with many other medicines. Surgery can cause bleeding, infection, or allergic reaction to anesthesia.

What happens after treatment for the condition?

Most patients with a deep venous thrombosis will recover fully. When DVT is in the pelvis or upper leg, warfarin is usually taken for at least 3 to 6 months. DVT in the veins of the calf is usually treated with warfarin for at least 6 weeks.

In people who develop a second DVT, warfarin treatment is continued for life. This long-term therapy is also used in people with underlying causes of DVT, such as cancer or a condition referred to as thick blood.

How is the condition monitored?

People with a history of deep venous thrombosis are told to avoid prolonged periods of immobility. They also need to watch for the common symptoms of leg pain and swelling. Individuals on blood-thinning medicines will have periodic blood tests to monitor the thickness of their blood. Any new or worsening symptoms should be reported to the healthcare provider.

Author:Minot Cleveland, MD
Date Written:
Editor:Ballenberg, Sally, BS
Edit Date:09/30/01
Reviewer:Eileen McLaughlin, RN, BSN
Date Reviewed:08/27/01

Sources