Deep Vein Thrombosis: What to Know

Deep vein thrombosis, commonly referred to as "DVT", is when a blood clot, or thrombus, develops in the large veins of the legs or higher up in the pelvic area. DVT's may cause no pain, or can be quite painful, but with prompt diagnosis and treatment, the majority are not life threatening. However, a clot that forms in the invisible "deep veins" can be an immediate threat to your life, as compared to clots of the more visible "superficial" veins that are visible below your skin. A clot that forms in these larger, deep veins is more likely to break free and travel through the vein. It is then called an embolus. When an embolus travels from the legs or pelvis to lodge in a lung artery, the condition is known as a "pulmonary embolism", or PE, a potentially fatal condition if not immediately diagnosed and treated.

What are the Causes of DVT?
Generally, a DVT is caused by a combination of two of three underlying conditions: 1) slow or sluggish blood flow through a major vein, 2) a tendency for a person's blood to clot quickly, and 3) irritation or inflammation of the internal lining of the vein. There are a variety of settings in which this clotting process can occur. First, individuals at bedrest (such as during or after a surgical procedure or medical illness, such as heart attack or stroke), or confined and unable to walk (such as during prolonged air or car travel) are common settings. It can occur in certain families in whom there is a history of parents or siblings who have suffered vein or other clots; or in whom active cancer or its treatment may predispose the blood to clotting. Recent major surgical procedures, especially those associated with hip and knee orthopedic surgery or those requiring prolonged bedrest, also predispose the blood to clotting. The third condition occurs when a leg vein is injured by a major accident or medical procedure. Also, there are specific medical conditions that may increase your risk of developing a DVT via these three mechanisms, such as congestive heart failure, severe obesity, chronic respiratory failure, a history of smoking, varicose veins, pregnancy and estrogen treatment. If you are concerned that you may be at risk due to any of these conditions, please consult with your physician.

Who is at Risk?
DVT occurs in about 2 million Americans each year and affects both men and women, all ethnic groups and all social levels. It is seen most often in adults over the age of 40, and more frequently in elderly patients, but can occur at any age. Women in the later stages of pregnancy or around the time of delivery are at increased risk. As noted above, other conditions may increase one's risk, and individuals who smoke and who do not exercise are at increased risk.

What Are the Symptoms of DVT?
Approximately half of those with a DVT never have recognized symptoms. When symptoms are present, the most common is leg pain and tenderness in the calf muscles, or one may observe swelling or a change in color of one leg to purple or blue. These signs and symptoms may appear suddenly or may steadily develop over a short time. If you observe these signs or symptoms, you should contact your doctor immediately. Symptoms are quite different if the clot breaks loose and travels to the lungs, causing a pulmonary embolism. The symptoms of PE include chest pain, shortness of breath, rapid pulse, or a cough. There may be a feeling of apprehension, sweating, or fainting. Such symptoms are not specific to a PE, and can occur with pneumonia, heart attack, and other important medical conditions. These are therefore always critical symptoms, which demand immediate medical attention.

How is DVT Diagnosed?
A suspicion of DVT is raised after a clinical exam and by identifying the associated risk factors, but a definite diagnosis of DVT, enough to guide treatment, cannot be accurately made without additional testing. An ultrasound scan of the legs is usually ordered, because it is highly accurate, non-invasive and painless. During the ultrasound scan, any blood clots in the vein are displayed on a monitor. A blood test may be performed to measure "D-dimer" as a sign of recent clotting anywhere in the body. When this test is negative, it is very unlikely that you may have suffered a DVT. However, even with these excellent tests, there are occasions requiring more accurate information for a diagnosis. A "venogram", a test in which dye is injected into a vein in the foot and an X-ray is taken, might be performed to most clearly view the blood flow within the leg veins. Venograms are rarely ordered today, but are helpful when deep vein thromboses are severe and when there may be a need to consider use of clot dissolving therapies or surgical therapies, as discussed below.

How is DVT Treated?
For most DVT's, physicians recommend wearing elastic compressive stockings, elevating the leg, and taking anticoagulant medications to prevent blood clotting. Anticoagulant therapy prevents further clots from forming and diminishes the risk of a pulmonary embolus. It consists of heparin, which may be given intravenously or, more frequently, by subcutaneous injection, followed by warfarin, which can be given orally and continued on an outpatient basis, usually for several months. In severe cases, the physician may recommend thrombolysis, which is the use of an intravenous medication that dissolves clots. With this procedure, a catheter is threaded up through the vein to the clot, and a clot-dissolving drug is injected to dissolve it. The clotbuster is injected slowly through a catheter with many tiny holes into the area of the DVT, much like a soaker hose. Sometimes a tiny vacuum cleaner is used to suck the softened clot out. Once the clot is gone, balloon angioplasty or stenting may be necessary to open the narrowed vein, but this is common only in the iliac veins, located in the pelvic area. With this approach, the patient will also need anticoagulant medication (heparin and warfarin) to prevent new blood clot formation. For a few patients who have valid reasons for clot removal but for whom clot-dissolving drugs cannot be used, extraction of the clot, through a small incision at the groin, may be recommended. Both approaches are designed to remove the clot and restore the venous blood flow but involve additional risk and expense and therefore are applied selectively by the appropriate vascular specialist. Clot removal, by either technique, is usually only recommended for major clots higher up in the leg, and particularly in active, healthy patients without any serious associated diseases. It can significantly reduce the serious consequences of DVT, such as chronic leg swelling, discoloration and, ultimately, ankle ulcers, but they do so at an increased risk of serious bleeding and are more expensive than anticoagulant therapy.

What Are the Late Effects of DVT's?
Smaller blood clots in the leg veins may dissolve without serious later consequences. However, larger blood clots, especially those located in the upper thigh and pelvic areas, are more likely to contribute to significant, long-term leg symptoms. The long-term consequences of a vein blood clot can persist even when the use of medications has, in the short-term, been "successful". For example, the leg veins can remain obstructed by remaining clot or scar tissue, or the valves in the vein may be damaged and not function properly. This may result in chronic swelling, skin discoloration, and ultimately, the development of chronic skin ulcers near the ankle. These problems can be diminished, if the individual who suffered a DVT will faithfully wear compressive leg stockings and elevate the legs periodically during the day. Anticoagulant medications will reduce the risk of future DVT and PE's, these medications cannot prevent the long-term tendency for leg swelling, discomfort, and skin changes, commonly called the "post-thrombotic syndrome" (PTS). These post-thrombotic symptoms are best treated by lifelong use of compressive leg garments. Unfortunately, it is not often appreciated that in some individuals, persistent leg swelling or discomfort may contribute to a real decrease in quality of life and even disable some individuals.

Can DVT's Be Prevented?
Regular exercise will decrease the risk of DVT. Persons who undergo major surgery are at risk to develop DVT, therefore calf and leg exercises before surgery and resuming physical activity as soon as possible after the surgery will decrease the risk for DVT. Preventing a DVT is the major reason why hospitals have patients up and walking as soon as possible after surgery. Regular stretching and leg movement are important for individuals who sit at a desk all day or are traveling on long trips, particularly air travel. As always, it is important to stop smoking, as smoking increases the tendency of the blood to clot and avoid wearing tight garments that produce constrictions below the waist.

For more information visit The American Venous Forum at www.venous-info.com