Deep Venous Thrombosis (DVT)

What is Deep Venous Thrombosis?

Deep venous thrombosis (DVT) means formation of a blood clot in the deep veins of the legs. Veins are the 'pipes' that bring blood back to the heart. In the legs, there are superficial veins (close to the skin) and deep veins (between the muscles). When the blood clots in these deep veins, it is called a DVT.

DVT is a major health concern. If not treated, the blood clots can get larger or break off and go the lungs. When this happens it is called a pulmonary embolism. The chance of dying from pulmonary embolism is over 25%.

Arm DVTs can occur but are much more rare than leg DVTs.

What causes Deep Venous Thrombosis?

There are many risk factors for DVTs. These can be grouped into one of three categories. These categories and the corresponding risk factors include:

1. Injury to the Deep Veins making them more likely to clot: trauma patients, surgical patients (especially orthopedic surgery and cancer surgery)
   
2. Immobility causing blood to pool and clot in the legs: hospital in-patient, post-surgical patients, prolonged travel (only mild risk factor)
   
3. Factors and diseases that increase the clotting of blood: cancer, pregnancy, age, history of past DVTs, genetic conditions causing increased clotting, oral contraceptive pill, hormone replacement therapy,

What are the symptoms of Deep Venous Thrombosis?

The most common symptoms of DVT are calf pain and swelling. It is well established that patients with these symptoms may not have a DVT and that patients with a DVT may have few symptoms. The first presentation might be of a pulmonary embolism. These symptoms include shortness of breath, chest pain, and palpitations.

Years after a DVT, as many as 20% of patients may develop post-thrombotic syndrome. This syndrome includes leg swelling, heaviness, pain and skin changes. These results from obstructed deep veins in the leg causing pressure-related complications.

Diagnosis and tests for Deep Venous Thrombosis

The most commonly used test for DVT is the duplex ultrasound. In this test, the veins of the leg can be directly visualized and assessed for the presence of clot. Other tests are only rarely used. These include CT scans, MRI, and contrast venography. In some settings, a physician may order a blood test called a D-dimer test. If this is negative, then it is unlikely that the patient has a DVT. However, a postive (or high value) has multiple causes hence further tests would be required in order to make the diagnosis of a DVT.

The most commonly used test for pulmonary embolism is a CT scan.

Lifestyle modification for Deep Venous Thrombosis

As noted above, the risk factors for DVT include immobility, trauma and disorders of blood that cause it to clot too quickly. Apart from encouraging early activity after surgery and avoidance of bedrest, there are few lifestyle changes that can prevent DVTs.

For patients who have had a DVT in the past and are now experiencing, leg heaviness, pain, or skin changes, compression stockings under the guidance of a physician is the most appropriate lifestyle modification.

Non-surgical and medical management for Deep Venous Thrombosis

Prevention: Patients at high risk for DVT include those undergoing surgery, hospital inpatients, trauma patients, and cancer patients. The use of blood thinners (oral or injectable) have been shown to reduce the risk of DVT and pulmonary embolism in these patients. Mechanical devices such as calf compression pumps can also be used to prevent DVT.

Treatment: When the diagnosis of a DVT or a Pulmonary Embolism has been made, treatment involves thinning the patients blood with medications: usually heparin (injectable) followed by oral medication (coumadin) for at least 3-6 months.

Guidelines for Intervention for Deep Venous Thrombosis

In patients who have a DVT but cannot be on blood thinners because of active bleeding or recent surgery, a mechanical filter can be placed in the major vein draing the lower body. These filters are placed via the groins using a large 'I.V' tube. Most modern filters are designed to be removed once it is safe to thin the patient's blood again.

Another reasons for intervention is when the veins of the upper leg and pelvis cause significant swelling that long-term function of the leg may be impaired. In some circumstances, physicians may recomment placing a clot dissolving medication into the veins through a large intravenous tube inserted into the leg.

Surgical treatment for Deep Venous Thrombosis

Surgical treatment for DVT is very rare. In some patients, clot in the veins of the upper leg and pelvis cause so much back pressure in the leg that the tissues cannot receive adequate oxygen and nutrients. Under these circumstances, surgery is performed to physically remove the clot.

Endovascular Treatment for Deep Venous Thrombosis

Endovascular treatment for DVT was discussed above under indications for intervention.

When should I see my doctor?

If you have risk factors for DVT and have any symptoms, you should consult your physician. He / she will consider your particular case and proceed with investigations if necessary. If you have have a DVT in the past and now have symptoms of leg aching and heaviness, you may be experiencing post-thrombotic syndrome. Your physician would be able to advise treatment or arrange for appropriate referral.

References and Resources

Rutherfords Vascular Surgery. 7^th Edition
Cronenwett and Johnston, eds.