Deep venous thrombosis

What is deep venous thrombosis (DVT)?

DVT is a blood clot (thrombus) that forms in the deep veins of the leg. The formation of the blood clot in the leg may be associated with pain and swelling. The major problem with DVT is that the clot may migrate to the lungs and cause difficulty in breathing and even death. Each year close to 200,000 people die from DVT which migrate to the lung (pulmonary embolism). Early recognition and appropriate treatment of DVT and PE can save many lives

Where are DVT most common?

DVT can occur in any vein in the body but are most common in the leg veins. It is the clots in the deep veins that are associated with complications. Clots in the superficial veins generally do not migrate and only cause localized pain.

What can cause deep venous thrombosis?

There are three essential elements that are required in the formation of a venous thrombosis. These are:

Prolonged stasis: Any condition that causes one to be in bed for prolonged periods (after surgery) or sitting in one place (flying in a plane) can lead to DVT

Vessel injury: Anytime a vein is injured, it is very prone to formation of blood clots

Hypercoaguability: There are some medical conditions (Protein C and S deficiency, lupus, etc) that can make one prone to formation of blood clots

What are common conditions associated with formation of venous thrombosis?

General:

Age

Immobilization > 3 days

During pregnancy and post delivery

After major surgery (especially hip fracture)

Long plane ride

Medical:

Anesthesia

Cancer

Stroke

Heart failure

Obesity

Use of birth control pill

Prior DVT

Trauma

Blood clotting problems

How may people develop DVT in North America?

Current data indicate that the true incidence of DVT suggest that about 80 cases per 100,000 persons occur annually (but this is an underestimate). DVT occurs in approximately 1 person per 20 over his or her lifetime, and 600,000 hospitalizations for DVT occur annually in the United States.

What are symptoms of DVT?

The signs and symptoms are related to the degree of obstruction and many individuals do not even know if they have a blood clot. In many cases, the body is able to break down the small clots but large clots may persist. The general features of a venous thrombus in the leg are:

Calf swelling

Pain in the calf (most prominent when moving the ankle)

Warmth of the skin around the calf

Shortness of breath (if clot has moved to lungs)

What are complications of a Deep venous thrombosis?

If a venous thrombosis is not adequately treated or missed, the following complication can result?

- Pulmonary embolism (blood clot moves into the lungs)

- Venous ulcer

- Swelling of the leg (post phlebitic syndrome)

How is diagnosis of DVT made?

The diagnosis of a deep vein thrombus is simple if it is suspected. The following are the most common tests:

Blood work: this involves routine blood work to ensure that your blood clotting parameters are normal. If you have had recurrent clots, then other special blood work will done.

Ultrasound: This is usually the first test done to look for a DVT. It is painless, fast and very effective in the diagnosis of DVT. It cannot look for blood clots which are underneath the groin. The test cannot differentiate between new and old clots either. Diagnostic accuracy varies depending on the technician performing the test.

MRI: This is never the first test of choice. It is useful if DVT is suspected and can look for DVT underneath the groin and in the major vein (Inferior vena cava) of the body. It can also visualize how far the clot has progressed from the legs into the abdomen. In pregnant females, it is the test of choice. However, is expensive and its use in pregnancy is questionable.

Venography: This is a rarely used test today because of the availability of ultrasound and MRI. It requires the use of a dye and exposure to radiation.



What is the treatment of deep venous thrombosis?

All individuals with a new diagnosis of a DVT need hospital admission and bed rest for at least 4-7 days.

Treatment is aimed to prevent:

- the thrombus from getting bigger

- prevent the clot from breaking loose and migrating to the lungs

- prevent the formation of new clots

- prevent the post phlebitic syndrome (DVT destroys the veins in the legs and even after

treatment, the leg remain swollen and tender)

Drugs: The initial drug treatment of a DVT is to immediately start a blood thinning medication called heparin. This medication is administered through an IV for about 2-4 days. The medication stabilizes the clots and prevents it from getting bigger. Once the blood clot is stabilized, you will be switched over to an oral medication (warfarin) and discharged home. These medications do not dissolve clots but do prevent the clot from increasing in size. Most individuals are maintained on warfarin for 6-9 months. Individuals who have recurrent DVT need life long anti coagulation therapy

What if I can not take warfarin?

In some individuals who are not able to take warfarin (pregnancy), a chemical similar to heparin, called low molecular weight heparin (LMWH), can be taken at home. LMWH are effective and have to be injected once or twice daily. They are slightly more expensive than warfarin.

Filters: There are some individuals who are not able to take anticoagulation medication because of the risk of bleeding or adverse side effects. In such cases, an umbrella-like device (inferior vena cava filter) can be placed. This device is placed under local anesthesia from either the veins in the groin in the neck. It captures the blood clots which may migrate to the lungs. These filters are viewed as a temporary solution.

Precautions

One should minimize activities that can cause injury while taking these blood thinners since bleeding and hemorrhage are a potential complication.

Prevention

Stockings: Elastic compression stockings should be worn if someone is going on a long flight or for surgery. Stockings relieve leg pain, swelling and prevent the post phlebitic syndrome. They must be worn everyday for at least 2-3 years after the DVT.

Activity: One should always remain active and ambulate on a daily basis. When traveling or flying, stretching and walking every few hours is highly recommended.

Hydration: Keep well hydrated