The main clinical concern with DVT is the potential of a thrombus (blood clot) to break free, travel through the inferior vena cava, through the heart, and get lodged in the vessels of the lungs. This event, called pulmonary embolism, carries a mortality rate of roughly 20 to 30%.

The formation of DVT’s can be attributed to one or more of the following factors: venous stasis (sluggish blood flow), injury of the blood vessel wall, or hypercoaguability (increased tendency of blood to clot).

Risk factors for DVT formation include age >40, obesity, smoking, pregnancy, trauma, IV drug use, or prolonged immobilization - such as due to chronic illness or long trips in cars or airplanes.

People with cancer, congestive heart failure, lupus, or recent heart attack or stroke are also prone to DVT’s. Recent surgery, chemotherapy, and hormone replacement therapy are risk factors as well.

Patients with DVT’s of the lower extremities have pain and swelling of the affected leg about 75% of the time. Other symptoms may include increased warmth and redness of the leg and occasionally low grade fever. DVT’s usually occur in the mid to upper leg.

The most commonly used test to check for DVT is duplex ultrasonography, which has very good sensitivity and specificity in certain patients. It is most reliable when used on patients who are symptomatic, especially when the symptoms are localized above the knee and below the groin. The most accurate test for DVT is venography, in which dye is injected into the veins of the involved leg. A blood test can also be done, which checks for D-dimer fragments. This test is of limited usefulness, however, as it has a high rate of false positives.

DVT’s are treated by administering anticoagulants (blood thinners) such as heparin or warfarin. Patients are generally started on heparin for immediate anticoagulation, and then continued on warfarin for 6 weeks to 6 months. Patients who are anticoagulated for 3 to 6 months have roughly on half the DVT recurrence rate of those who are anticoagulated for only 4 to 6 weeks. Anticoagulants are contraindicated in patients with active bleeding or bleeding disorders. These patients may benefit from placement of a Greenfield filter in the inferior vena cava. By placing a filter in the vessel which returns blood from the legs, any thrombi are screened out before they can get lodged in the vessels of the lungs.

Unless one succumbs to the complication of DVT, such as a massive pulmonary embolism, the outcomes in patients are good.