Blood clots that form in the coronary arteries cause heart attacks. However, many people don't realize that clots also can form in other parts of the vascular system—particularly in the deep veins of the legs, causing deep vein thrombosis (DVT). These clots can be even more dangerous than clots in the coronary arteries because they are more likely to go undiagnosed.

Of the 200,000 Americans who die each year from clots due to DVI about 807o of them experience no symptoms. The worst danger of DVT is pulmonary embolism, in which one or more clots travel from the legs to the lungs. One in five people who experience a pulmonary embolism dies from it.

Clots that form in veins near the surface of the skin (superficial thrombosis) are rarely serious. But those that form in the deep veins in the legs—particularly in the femoral (thigh), iliac (groin) or popliteal (behind the knee) veins—are often life-threatening. They rarely dissolve on their own. If anything, they're likely to keep growing—and eventually break free and travel to the lungs.

Even for patients who survive a pulmonary embolism, the risk for complications is high. About 4% to 5% will go on to develop pulmonary hypertension (high blood pressure in the lungs). Others are at risk for venous insufficiency, in which the leg veins are damaged, resulting in chronic leg swelling, skin thickening and skin ulceration.


About 10% of patients with DVT have a genetic tendency to form blood clots. Other risk factors...

  • Prolonged periods of inactivity can allow dangerous blood clots to form. This can occur during lengthy (more than five hours) plane flights or car trips. Long-distance air or car travelers who have other risk factors, such as congestive heart failure, previous heart attack, obesity or a history of previous blood clots, are at even greater risk than healthy people of developing DVT.

Orthopedic surgery, particularly hip or knee replacement, causes immobilization, often for days to weeks. Anticlotting drugs are given to prevent clots from forming.

  • Lung, pancreatic or ovarian cancer. Patients with these cancers have increased levels of procoagulants, substances in the blood that promote clotting.
  • Pregnancy and childbirth. Pulmonary embolism is a cause of death in women during childbirth. Many women who die from pulmonary embolism during or soon after childbirth may have an underlying genetic disorder that increases the risk for clots.

Women who take the breast cancer drug tamoxifen or supplemental estrogen in birth control pills or hormone therapy also are at increased risk for DVT and pulmonary embolism.


Although patients with DVT frequently do not have symptoms, when clots completely block a vein, persistent symptoms of leg swelling, redness, increased warmth and pain develop.

Red flag: A pulmonary embolism from DVT typically causes sudden shortness of breath, chest pain or a cough that produces blood-tinged mucus. If you experience these symptoms, get to an emergency room immediately. About 10% of patients with pulmonary embolism die within one hour.

DVT usually can be diagnosed with ultrasound, a painless, 30-minute test that uses high-frequency sound waves to view the veins.

If your doctor suspects that you have a pulmonary embolism, he/she may recommend a pulmonary computed tomography (CT) scan, in which a dye is injected into an arm vein and computerized images are taken as the dye passes through the blood vessels in the lungs. Most patients require medication to prevent the clot from growing-and to prevent additional clots from forming.

Typical treatment approaches…

  • DVT patients with a pulmonary embolism who are hemodynamically stable—that is, their blood pressure and level of oxygen in the blood are close to normal—are hospitalized for five to seven days and treated with intravenous heparin, an anticoagulant medication.

Recent development: A new formulation known as low-molecular-weight heparin, which is better absorbed and lasts longer than intravenous heparin, can be given as a subcutaneous shot at home for five to seven days.

After one of these initial treatments, warfarin (Coumadin) is given for three to six months.

  • DVT patients with a pulmonary embolism who are hemodynamically unstable are at the greatest risk for death—they have low blood pressure and poor oxygen saturation. These patients are typically given tissue plasminogen activator (tPA), an intravenous, clot-dissolving drug that is often used to treat stroke patients. This therapy is followed by intravenous or subcutaneous heparin for five to seven days. Warfarin is then given for three to six months to prevent recurrent clots.

In rare cases, when a patient can not receive anticoagulant therapy because of bleeding, recent surgery or an allergy to the medication, doctors may use a vein filter, a small metal trap that's inserted into the inferior vena cava (the large vein that carries blood from the lower part of the body to the heart). The filter prevents pulmonary embolism by catching clots before they can be carried to the lungs.


Patients at risk for DVT who are hospitalized and bedridden are usually treated with subcutaneous heparin.

If they cannot take heparin, they may be fitted with graduated compression stockings or external pneumatic compression sleeves (which inflate and deflate every 30 seconds by air compression). Both exert varying amounts of pressure along the legs to keep blood from pooling in the legs and forming clots.

Other ways to prevent DVT...

  • Rotate your ankles and flex your toes at least every 20 minutes when traveling by plane or car. On airplanes, periodically stand and rise up on your tip-toes repeatedly. These exercises flex the calf muscles, which pushes blood out of the legs and helps prevent DVT.
  • Walk daily. Walking, like other forms of leg exercise, keeps blood moving upward out of the leg veins. The more that blood moves, the less likely it is to form unwanted clots. It's particularly important for hospitalized patients to attempt to walk with appropriate supervision or at least move their legs while they're in bed.

Recent studies indicate that about 15% of hospitalized patients get DVT. Bedridden patients also should flex their feet, ankles and calves every 20 to 30 minutes when awake for clot prevention.

  • Drink water. Airplane and car travelers on trips of five hours or more should drink two to four eight-ounce glasses of water during the flight or car ride. This increases blood volume, which may help prevent blood clotting.

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