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.” The Coalition to Prevent Deep-Vein Thrombosis is funded by sanofi-aventis U.S. LLC US.ENO.08.01.024 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. The Coalition to Prevent Deep-Vein Thrombosis is funded by sanofi-aventis U.S. LLC US.ENO.08.01.024 2 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 US.ENO.08.01.024 3 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. The Coalition to Prevent Deep-Vein Thrombosis is funded by sanofi-aventis U.S. LLC US.ENO.08.01.024 4