What is Deep Vein Thrombosis (DVT)?

Deep vein thrombosis (DVT) occurs when a blood clot, or thrombus, develops in the large veins of the legs, pelvic area, or arms. Only half of those with DVT will have typical symptoms of leg or arm swelling and pain. In rare cases, DVT may also occur in the veins of the arms. With prompt diagnosis and treatment, the majority of DVTs are not life-threatening. However, if the blood clot breaks loose and travels through the heart to the lung, a condition known as a pulmonary embolism (PE) occurs. If the traveling clot, called an embolus, clogs the main lung artery, it can be fatal. On average, an estimated 650,000 PEs occur annually, placing it as the third most common cause of hospital death.

More people suffer from DVT annually than from heart attack or stroke. Each year up to two million Americans are affected by DVT and up to 600,000 are hospitalized. DVT affects 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 for 4-6 weeks after delivery are at increased risk. Other conditions may also increase one's risk, and individuals who smoke or are immobile are at increased risk.

How Is DVT Diagnosed?
The most commonly used method for diagnosing DVT is by an ultrasound exam. This simple, painless test is safe and widely available. A specific blood test may also be performed to measure "D-dimer," which is a sign of recent clotting. When this test is negative, it is unlikely that DVT has occurred.

What Are the Causes of DVT?
DVT is generally caused by a combination of two or three underlying conditions:

• slow or sluggish blood flow through a deep vein
• a tendency for a person's blood to clot quickly (also called a hypercoagulable state or thrombophilia)
• irritation, inflammation, or injury to the inner lining of the vein

There are a variety of settings in which this abnormal clotting process can occur. These include individuals on bed rest (such as during or after a surgical procedure or prolonged medical illness, such as heart attack or stroke) or those who are confined and unable to walk for prolonged periods of time (such as the confining environment of air or car travel). It can also occur in certain families with a history of parents or siblings who have suffered from prior blood clots. It has been found to occur in individuals who have active cancer or are undergoing cancer treatment, which may predispose the blood to clotting. A recent major surgical procedure, especially hip and knee orthopedic surgeries, or any treatment that requires prolonged bed rest, also predisposes the blood to clotting. Additionally, irritation or inflammation occurs when a leg vein is injured by a major accident, surgical procedure or invasive medical procedure.

Also, there are specific medical conditions and other factors 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 in the form of birth control pills or hormone replacement therapy. If you are concerned that you may be at risk due to any of these conditions, you are encouraged to consult with your physician.

Treatment:
Both DVT and PE are treated with blood-thinning medication. These medicines, called anticoagulants, decrease your blood's ability to clot and can also stop clots from getting bigger. The use of medication may also prevent new clots from forming. They do not, however, break up existing clots that have already formed. The body's natural systems will help dissolve the clot to varying degrees. The length of time the patient is treated with anticoagulants depends on a number of factors, and is determined by a physician.

Some doctors may recommend sequential compression devices to promote blood flow after surgery-particularly orthopedic surgery such as hip or knee replacement. 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. A newer subcutaneous injection medication can also be used to treat blood clots. Warfarin (Coumadin®), which can be given orally, is continued on an outpatient basis.

The physician may also recommend thrombolysis, using an intravenous agent that dissolves blood clots. This medication is given by a catheter that is threaded up through the vein to the clot, and one of the clot-dissolving drugs is injected to dissolve it. The clotbuster is injected slowly through a catheter (which has many tiny holes) into the area of the DVT, much like a soaker hose. Sometimes a tiny vacuum cleaner type of device is used to suck out the softened clot. Once the clot is gone, balloon angioplasty or stenting may sometimes be necessary to open the narrowed vein, but this is common only in the larger veins, located in the leg or pelvic area. With this approach, the patient will also need anticoagulants to prevent new blood clot formation while the existing clot is being dissolved.

For some patients, extraction of the clot (thrombectomy), through a small incision at the groin, may be recommended. These approaches are designed to remove the clot and restore the venous system to normal, but they involve additional risk and expense and therefore are applied selectively by the appropriate vascular specialist. Clot removal, by either technique, is usually recommended only 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 late after-effects of DVT in the legs, such as chronic leg swelling, discoloration and, ultimately, ankle ulcers, but it does so at an increased risk of serious bleeding.

Current recommendations are that all patients with leg DVT wear a prescription support stocking to help decrease the risk or treat symptoms of leg swelling. The stockings also help to prevent the skin changes that can occur over time (as mentioned above) including skin irritation, skin discoloration, scarring, and leg ulcers. This condition is called post-thrombotic syndrome.

Can DVT Be Prevented?
Persons who undergo major surgery are at risk to develop DVT; therefore, exercising the calf and leg before surgery and resuming physical activity as soon as possible after surgery will decrease the risk for DVT. Preventing 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 in a confined space on long trips, such as in air travel. Other recommendations are to refrain from smoking cigarettes and to maintain a normal body weight. If you are in the hospital for any reason and have any of the risk factors mentioned above, you should discuss prevention of clots with your physician.

Sometimes patients cannot take blood thinners or have recurrent clots on blood thinners. These patients may have a vena cava filter placed in the major vein in the abdomen (which drains blood from the legs). This is a device which stops clots from traveling to the lungs.

About the Author: Robert B. McLafferty, MD Dr. McLafferty is the Professor of Surgery for Southern Illinois University School of Medicine, Division of Vascular Surgery. He is a well-known expert and national speaker at numerous conferences and other events on venous diseases.