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When traveling by car, "Don't take a 10-hour trip without stopping every couple of hours," says Stein. "Get out and walk a bit." Even if you're the driver, you still need to take walking breaks, he says. "Pushing on the gas pedal isn't enough activity even for the one leg."

"Deep vein thrombosis went unrecognized for decades because the clots that formed in the large veins in the legs often started coming off in little pieces after a person had been home for a day or two," says Mohler, "so they would go to the emergency room with a suspected possible heart attack."

Chest pain can be a symptom of both heart attack and pulmonary embolism. Other common symptoms of pulmonary embolism are unexplained shortness of breath and coughing up blood. It's important to tell your doctor if you have taken a long trip recently, says Mohler, so you can be diagnosed correctly.

If you have any symptoms of pulmonary embolism, sit down and tell someone you have an emergency and need immediate help, says Stein. At that point, "there is no value in putting your feet up or drinking gallons of water. Getting to an emergency room quickly is your best shot."

Another potential complication of DVT is post-phlebitic syndrome, a permanent condition caused by valves in the leg veins that don't work properly. "The body has mechanisms within itself to dissolve clots, but it's a very slow process," says George Shashaty, M.D., an FDA hematologist. "In the interim, an inflammatory reaction occurs that can scar the veins, especially the valves." The valves then fail to prevent blood from flowing backwards, allowing the blood to pool in the leg veins and cause pain, swelling, and sometimes varicose veins and skin ulceration.

Diagnosis and Treatment

A commonly used FDA-approved medical test to diagnose DVT is the duplex ultrasound, says Sapirstein. A handheld device is passed back and forth on the surface of the affected area, sending sound waves from the body to a machine that generates and displays a picture of the blood flow on a video screen for a doctor to evaluate.

Another less commonly used test, venography, may be done to diagnose DVT if ultrasound does not give a clear diagnosis, says Sapirstein. A dye is injected into a vein, which makes the blood flow visible when an X-ray is taken.

Duplex ultrasound, chest X-rays, and other tests may be used to diagnose a pulmonary embolism. "The primary treatment for deep vein thrombosis and pulmonary embolism is blood thinners," says Sapirstein. Blood thinners, or anticoagulants, such as heparin, will not dissolve clots already formed, but will keep them from growing and prevent new ones from forming. Heparin may be given as an injection below the skin surface or into a vein (intravenously).

People at risk for DVT may be prescribed the blood thinner Coumadin (warfarin) to keep clots from growing. Warfarin is currently the only FDA-approved blood thinner taken orally. "Other agents are being developed as oral anticoagulants but aren't on the market yet," says Kathy Robie-Suh, M.D., Ph.D., an FDA internist. Warfarin interacts with many other medications. "If you are on warfarin, the doctor needs to know all the other medications you are on, including over-the-counter," says Robie-Suh, and patients should make sure they take their warfarin before going on a trip. People who have had one deep vein clot are prone to getting more.

"When a patient cannot tolerate blood thinners or continues to develop clots, then you have to go to an alternative, such as a filter," says Sapirstein. The FDA has cleared medical filters, such as "umbrella filters," that a surgeon can insert into the vena cava, a large vein in the abdomen that returns oxygen-depleted blood to the heart. The filter is inserted in a folded position and then springs open against the vein walls to keep the vein open for blood flow. The filter does not keep blood clots from forming, but it prevents their passage from the veins in the lower extremities to the heart and lungs. These filters may either remain in place permanently or be removed later.

Another treatment alternative for pulmonary embolisms is administering one of the FDA-approved thrombolytics. These potent drugs, known as "clot-busters," are given intravenously to quickly dissolve large clots that are unlikely to break up on their own. They are used only in life-threatening situations because they may cause sudden and severe bleeding.

What Makes Deep Vein Thrombosis More Likely?

• an inherited condition that causes increased risk for clotting
• low blood flow in a deep vein due to injury, surgery, or being immobile
• cancer and its treatment
• other medical conditions, such as varicose veins
• sitting for a long period of time, as on long trips
• pregnancy and the first six weeks after giving birth
• being older than age 60
• being overweight
• taking birth control pills or hormone therapy
• having a medical condition that requires a tube placed in a vein to allow easy access to the bloodstream for medical treatment (central venous catheter).

Facts About Deep Vein Thrombosis and Pulmonary Embolism

• Nine out of 10 cases of pulmonary embolism are caused by blood clots that form in the legs and then travel to the lungs.
• More than 600,000 people in the United States have a pulmonary embolism each year, and more than 10 percent of them die from it.
• Most who die do so within 30 to 60 minutes after symptoms start.
• Pulmonary embolism occurs equally in men and women.
• The risk of having a pulmonary embolism doubles for each 10 years after age 60.

Tags: Health

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www.fda.gov
FDA is A United States government body that oversees medical devices, including contact lenses, intraocular lenses, excimer lasers and eyedrops. In the US, these products must be approved by the FDA before they can be marketed.