Disease Backgrounder What Is Deep-Vein Thrombosis?

Disease Backgrounder
What Is Deep-Vein Thrombosis?
Deep-vein thrombosis (DVT) occurs when a thrombus (blood clot) forms in one of the large
veins, usually in the lower limbs, leading to either partially or completely blocked circulation. A
DVT blood clot has the potential to move into the lungs and block circulation to this vital organ
creating a life threatening condition – known as pulmonary embolism (PE) – requiring
immediate medical attention.
Up to two million Americans suffer from DVT annually1. Approximately 600,000 Americans are
hospitalized each year for DVT and its primary complication, PE1. DVT-related PE is the most
common cause of preventable hospital death2. Approximately 300,000 die from PE3, the majority
of which result from DVT4. Complications from DVT kill more people each year in the United
States than breast cancer and AIDS combined1.
Venous thrombosis in the lower limb can involve the superficial leg veins; the deep veins of the
calf (calf vein thrombosis); or the more proximal veins, including popliteal veins, the superficial
femoral, common femoral, and iliac veins. Less commonly, thrombosis involves other veins in
the body. Unlike the superficial veins just below the skin surface, most of the deep veins are
surrounded by powerful muscles that contract to force blood back to the heart. One-way valves
inside the veins prevent backflow of blood between muscle contractions. When the rhythm of
circulation slows down due to illness, injury or inactivity, there may be a tendency for blood to
accumulate or “pool.” A static pool of blood provides an ideal environment for clot formation.
Who Is at Risk for Deep-Vein Thrombosis?
Certain individuals may be at increased risk for developing DVT; however, DVT can occur in
almost anyone. Risk factors or triggering events include, but are not limited to2:
• Congestive heart failure or respiratory failure
• Restricted mobility
• Cancer
• Infection
• Obesity
• Age > 40 years
• Surgery
• Varicose veins
• Prior history of VTE (e.g. DVT or PE)
• Chronic lung disease
• Inflammatory bowel disease
• Smoking
What Are the Signs and Symptoms of Deep-Vein Thrombosis5?
Symptoms of DVT may include pain, swelling, tenderness, discoloration or redness of the
affected area, and skin that is warm to the touch. However, as many as half of all DVT episodes
produce minimal symptoms or are completely “silent.”
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Because a number of other conditions – including muscle strains, skin infections and phlebitis
(inflammation of veins) – display symptoms similar to those of DVT, the condition may be
difficult to diagnose without specific tests.
How Is Deep-Vein Thrombosis Diagnosed?
Although a number of tests have been evaluated over the years, experts agree that only three
have been shown to have special value for diagnosing DVT in symptomatic patients: venous
ultrasonography, venography and impedance plethysmography (IPG).
•
Venous Ultrasonography of the venous system is obtained with high-resolution
equipment to produce two-dimensional images of reflected signals from an array of
ultrasound sources, including the common femoral vein in the groin and the popliteal
vein, which connects to the femoral vein. Gentle pressure is applied with the probe to
determine whether the vein under examination is compressible. The most accurate
ultrasonic criterion for diagnosing venous thrombosis is non-compressibility of the
venous lumen (cavity) under gentle probe pressure.
•
Venography is performed by injecting radiographic material into a superficial vein on
the top of the foot. The contrast material mixes with the blood and flows through the leg.
An X-ray image of the leg and pelvis will show the calf and thigh veins, which drain into
the external iliac vein. A clot is diagnosed by the presence of an intraluminal filling
defect, an abrupt cut-off of the contrast material on the X-ray.
•
Impedance plethysmography (IPG) is performed by placing two sets of electrodes
around the patient's calf and an oversized blood pressure cuff around the thigh. The
electrodes sense a change in blood volume, which is recorded on a strip chart. Changes in
venous filling are produced by inflating the thigh cuff to obstruct venous return and then
reestablishing blood flow by deflating the cuff and assessing the time taken for venous
volume in the calf to return to baseline. If a clot is present in the popliteal or more
proximal veins, venous emptying is delayed.
What Is Pulmonary Embolism?
The major risk associated with DVT is the development of a pulmonary embolism (PE). A PE
can occur when a fragment of a blood clot breaks loose from the wall of the vein and migrates to
the lungs, where it blocks a pulmonary artery or one of its branches.
As noted above, approximately 300,000 die from PE3, the majority of which result from DVT4.
Complications from DVT kill more Americans each year than breast cancer and AIDS
combined1.
Blockage of the main pulmonary artery by one or more of the emboli may be life-threatening.
Symptoms may include shortness of breath, a feeling of apprehension, rapid pulse, sweating,
and/or sharp chest pain that worsens with deep breathing. Some patients may cough bloody
sputum, while others may develop very low blood pressure and pass out. A number of serious
conditions – including an evolving heart attack and pneumonia – may mimic PE5.
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How Can Healthcare Providers Reduce the Risk and/or Treat Deep-Vein Thrombosis and
Pulmonary Embolism?
Effective prophylaxis and treatment options exist for both DVT and PE.
Anticoagulants, or blood-thinning drugs, are commonly used to reduce the risk of and treat DVT.
These agents work by altering the body’s normal blood-clotting process and may help to reduce
the risk of PE. With early treatment, patients with DVT may reduce their chances of developing
PE to less than one percent.
How Does a Venous Thromboembolism Compare to DVT?
Venous thromboembolism (VTE) refers to two serious conditions: DVT and PE. DVT occurs
when a thrombus (blood clot) forms in one of the large veins, usually in the lower limbs, leading
to either partially or completely blocked circulation. A DVT blood clot has the potential to move
into the lungs and block circulation to this vital organ, creating a life-threatening condition –
known as pulmonary embolism (PE) – requiring immediate medical attention. PE occurs when
the clot escapes into the circulation and becomes lodged in the lungs, obstructing the pulmonary
artery, or its branches, which supply the lungs with blood. If the clot is large and completely
blocks a vessel, it can cause sudden death.
Other Related Facts & Figures
Some Causes of Death in the U.S.
Pulmonary embolism
AIDS
Breast cancer
Estimated Annual
Deaths
Approximately
300,000
17,011
40,910
•
More people suffer from DVT annually than from heart attack or stroke.
•
Approximately 600,000 people are hospitalized in the United States each year for DVT and
its primary complication, PE.
•
DVT-related PE is the most common cause of preventable hospital death.
•
Only one-third of hospitalized patients with risk factors for blood clots received prophylactic
DVT treatments, according to a U.S. multi-center study.
•
Without prophylactic DVT treatment, up to 60 percent of patients who undergo total hip
replacement surgery may develop DVT.
•
Cancer patients undergoing surgical procedures have at least twice the risk of postoperative
DVT and more than three times the risk of fatal PE than non-cancer patients undergoing
similar procedures.
•
In the elderly, DVT is associated with a 21 percent one-year mortality rate, and PE is
associated with a 39 percent one-year mortality rate.
The Coalition to Prevent Deep-Vein Thrombosis is funded by sanofi-aventis U.S. LLC
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1
Gerotziafas GT, Samama MM. Prophylaxis of venous thromboembolismin medical patients. CurrOpin PulmMed.
2004;10:356-365.
2
Geerts WH,Pineo GF, Heit JA, et al. Prevention of venous thromboembolism: The Seventh ACCP Conference on
Antithrombotic and ThrombolyticTherapy. Chest.2004;126(suppl):338S-400S
3
Heit et al. Am Soc Hematol. Presented at: 47th Annual Meeting and Exposition, American Society of Hematology;
December 2005; Atlanta, GA, Poster [68].
4
Murin et al. Thromb Haemost. Comparison of the Outcomes after Hospitalization for Deep Venous Thrombosis
or Pulmonary Embolism. 2002; 88: 407-14.
5
American Public Health Association. Presented at: Public Health Leadership Conference on Deep-Vein
Thrombosis: February 26, 2003: Washington, D.C. White Paper.
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