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What you need to know about deep vein thrombosis

March is DVT Awareness Month

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Deep vein thrombosis, or DVT, occurs when a blood clot forms in the large veins of the legs or pelvic region. If the clot breaks loose and travels to the lungs, a pulmonary embolism (PE) may result.

According to national estimates, approximately 900,000 people are affected by deep vein thrombosis and pulmonary embolism each year. Dr. Thomas Wakefield, head of vascular surgery at the University of Michigan, says identifying the patient’s risk factors is important in preventing DVT. “If there is a risk, you can modify and reduce that risk in many cases.”

Who’s at risk for DVT?

Risk factors for DVT and PE include:

  • Advanced age
  • Active cancer and cancer treatments
  • Immobility, paralysis
  • Recent trauma, surgery or hospitalization
  • Family history or personal history of DVT or PE
  • Pregnancy and the time period around delivery
  • Oral contraceptives and hormone replacement therapies
  • Obesity
  • Chronic medical conditions
  • Infections
  • Inherited and acquired blood clotting abnormalities
  • Smoking (in some studies)

Anyone can develop DVT; however, the more risk factors you have, the greater your chances of developing the condition, says Dr. Wakefield. Hospitalized patients are at a high risk for DVTs and PE, with risk factors varying depending on the reason for the hospitalization, the seriousness of the illness and any surgery that was performed. For example, hip-replacement patients may develop DVT or a PE if they fail to receive appropriate preventive therapy.

Wakefield says the aging population is also at a higher risk for deep vein thrombosis. “As we age, the risk becomes greater, which is why DVT awareness is so important.”

Symptoms of deep vein thrombosis

One of the most common symptoms of DVT, says Dr. Wakefield, is often what feels like a pulled muscle in the calf or thigh. “Patients realize after a few days that the ‘muscle pull’ is not getting better and can’t be ‘explained away’.” Some people experience pain or swelling in their leg, while others experience few symptoms initially.

Signs of DVT, according to Wakefield, include:

  • Sudden leg swelling or pain
  • Significant calf swelling that does not improve
  • Redness or discoloration
  • Skin that is warm to the touch
  • Tenderness over the course of the vein

Symptoms of pulmonary embolism

Because PE can be fatal, Dr. Wakefield stresses the importance of seeking immediate medical attention. Common symptoms include:

  • Sudden and severe shortness of breath
  • Heart pain or palpitations
  • Collapsing or feeling faint
  • Coughing up blood

Diagnosing and treating DVT

According to Dr. Wakefield, ultrasound is the “gold standard” for diagnosing DVT. “It is a non-invasive test and provides a highly accurate diagnosis.” Other methods include measuring biomarkers (a blood measurement to detect the presence of a particular disease), which can help determine a high or low probability of DVT, and performing a clinical risk assessment. “The research involved with biomarker measurement is ongoing at Michigan,” says Dr. Wakefield.

Because DVT/PE sometimes exhibits no symptoms, it can go untreated, which can be fatal. In fact, DVT/PE is the fourth leading cause of death in western society (especially PE), with more fatalities than breast cancer, AIDS and traffic accidents combined.

To keep a pulmonary embolism from happening once a DVT is found, doctors will often prescribe a blood-thinning drug that helps the body to stabilize the DVT clot and prevents more clots from forming. Compression stockings can also be worn to help move blood from the legs and decrease the long-term detrimental effects from the clot.

In some patients, doctors may remove a DVT by threading a tiny catheter into the vein, using a device to mechanically disrupt the clot and infusing specialized medications to help dissolve the clot. In clots in the upper leg and pelvis, such treatments will reduce the chance of more clots forming and decrease the long-term adverse effects of leg pain and swelling from the clot.  A new clinical trial at the University of Michigan and throughout the nation is comparing this approach to blood-thinning drugs alone. This same approach may be used for life-threatening pulmonary embolisms.

How do I prevent DVT?

DVT can be prevented in many cases through regular activity, healthy eating and talking to your health care provider about preventing blood clots before any surgical procedures or hospitalizations. When diagnosed and treated early enough, DVT is usually not life threatening.

What if I can’t take blood-thinning medicines?

Patients who have a high risk of pulmonary embolism and can’t take blood-thinning medicine can be treated by having a wire filter device that catches clots implanted in the vena cava, the large vein that leads from the lower body to the heart.

In 1973, the first such filter was developed by Lazar Greenfield, M.D., who is now an emeritus professor of surgery at U-M. Many varieties of permanent and removable filter devices are available today.