Understanding DVT

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What is a DVT?

DVT is an abbreviation that stands for Deep Vein Thrombosis. Simply put, it is a blood clot. If there is only one clot it is called a thrombus; if there are several clots they are called thrombi. Blood clots occur in the larger deep veins and most commonly the deep veins of the legs, pelvis or arms. When a clot forms in a deep vein, it causes re-routing of the blood flow and a build up of pressure. When this happens, it can lead to swelling and can be painful because the blood flow to the heart is being blocked.

 

What Causes DVT?

As you have learned, thrombosis means clot. There are a number of reasons why clots can form in the deep veins. Long ago it was recognized that clots form in veins for three basic reasons:(1) damage to the vein wall; (2) lack of blood movement (also called stasis), and; (3) an increased tendency to form a clot, known as hypercoagulability.

Damage to the veins can happen in a number of settings, including recent surgeries, accidents, trauma, or injury.

Stasis occurs when a person is immobilized for any number of reasons, including hospitalization, confinement in a nursing home or rehabilitation, sitting in an airplane or car for long periods of time without movement, or having your leg in a cast, as an example.

Finally, and perhaps the least understood, is shypercoagulability. There are certain people who for one reason or another simply have a predisposition to form blood clots. Sometimes this is due to a genetic defect in which the body does not have the right balance of coagulation factors that either create or more likely, break down clot once it occurs.1 In addition to genetic factors, some patients acquire a propensity to form clots. This is very common in some types of cancer and other diseases.

How Common is DVT?

DVT is more common in individuals with risk factors. Commonrisk factors for DVT include surgery, hospitalization for acute
(long-term) medical illness, nursing home confinement, trauma, active cancer, orthopedic surgery, auto immune disorders and any procedure in which a plastic catheter is inserted into the vein. Women have an additional risk for developing a DVT. High estrogen states including oral contraceptives or hormone replacement therapy, and pregnancy are all significant risk factors to developing a DVT.4 Studies show a PE is the leading cause of maternal death associated with childbirth. DVT has also been associated with long air plane flights.

How Do I Know if I Have DVT and How is it Diagnosed?

The most common symptoms of DVT are pain in the calf, increasing with standing and walking as well as swelling of the lower leg. In general, the symptoms are constant in nature, meaning they do not come and go. Unfortunately, only about half of people with a DVT have a combination of the symptoms. Some patients have no symptoms at all.

When a DVT is suspected, the health care provider will take a thorough medical history and perform a physical examination including asking questions about any family history of blood clots or bleeding problems. A number of tests are available to check for a DVT. The most common exam performed is a vascular ultrasound. This is a non-invasive imaging study where ultrasound images are able to determine if there are blood clots in the leg veins.6 It is a safe and accurate test. Sometimes it will be performed in conjunction with a blood test. In a few cases, more advanced imaging techniques such as Venography, CT scan or MRI are utilized to look at the deeper veins. In general, if you are concerned about the possibility of a blood clot in your leg, call your physician or seek immediate medical attention.

Other Risks of a DVT?

One of the most dangerous complications of a DVT is that the clot (embolus) can break free in the vein and travel to the lungs. This is known as a Pulmonary Embolism, or what health care workers call a PE. A Pulmonary Embolism can be a fatal complication of a DVT. Please note that all PE’s are not fatal. What determines the seriousness of a PE is the size of the clot and which pulmonary artery is blocked. Blocking blood flow in the lungs will cause heart failure. When you are diagnosed as having DVT, the doctor will often assess the risk by determining the size of the vein with the clot. Usually, the closer the vein is to the heart or lungs the bigger the vein, which in turn means potential for a larger clot. This increase in size increases the risk should an embolus break loose.

Compression Stockings and Diagnosis of DVT?

Evidence suggests that the risk of Post Thrombotic Syndrome can be significantly reduced by the routine use of graduated medical compression stockings after a DVT. Graduated compression stockings are, therefore, very important in the treatment of DVT. Ideally, a person with a new diagnosis of DVT should wear a graduated compression stockings immediately after the time of diagnosis. Wearing the stockings helps to minimize swelling and it can also improve the long-term health of the leg.

It is important that high-risk ambulatory patients wear true graduated compression stockings with a minimum compression level of 20-30 mmHg, as opposed to anti-embolic stockings (sometimes referred to as TED hose) which, depending on the manufacturer, deliver in the range of 8-18 mmHg. When a patient is up and walking, the pressure generated in the veins after a DVT can be significantly higher than when they are laying down. The primary difference between anti-embolic and graduated compression stockings is that anti-embolic are designed for a bed-ridden patient and graduated compression stockings are for patients who are able to walk and require a higher compression level to aid the venous blood flow, against the pull of gravity, back to the heart and lungs. The increased compression appliedto the leg allows for better control of symptoms, especially swelling, aching and tiredness.

Graduated medical compression stockings should be worn for up to 2 years (or longer when the patient is at “high risk”) after the time of diagnosis to help prevent or manage the symptoms of Post Thrombotic Syndrome. The stocking should be put on in the morning and taken off in the evening. It is important to remember that the elasticity in the compression stocking decreases over time, and therefore new stockings should be purchased every 4-6 months. Proper care can extend the life of the stockings.

How Can I Prevent DVT?

In most cases, Deep Vein Thrombosis is a preventable disease. People undergoing surgery and in the hospital for an extended period of time may be at risk for developing blood clots. Your health care provider will guide you on the best ways to minimize your risk of developing DVT in these situations.13 If you are not hospitalized, you can still develop blood clots. Smoking cessation, weight loss and exercise can decrease your risk of developing a blood clot. When you travel for a long period of time (over 4 hours), you are at increased risk of developing a blood clot. You can decrease this risk by getting up and walking or doing foot flexes every 30 minutes. For people with no severe venous insufficiency, wearing a low level (15-20 mmHg or 20-30 mmHg) of graduated compression stockings while traveling has been shown to decrease the rate of blood clots in the legs. Remember, if you have had a prior blood clot, you are at increased risk of developing another blood and should wear a 20-30 mmHg or higher graduated medical compression stocking.

Vascular Screeing Exams

If you have any of the following risk factors, you may have vascular disease or be at risk for DVT:

• Do you have high blood pressure or do you take medication for high blood pressure?
• Do you smoke or have a long history of smoking?
• Do you have diabetes?
• Do you have pre-existing heart disease?
• Do you have high cholesterol or do you take medication for high cholesterol?
• Is there an immediate family history of stroke, aneurysm or heart disease? (mother, father, siblings, children)
• Do you eat a diet high in saturated and/or animal fat?
• Are you over 50 years of age?

These are for the most part the same risk factors as those for heart disease and stroke.

If so, you may want to consider a vascular screening exam. Our aim is to identify those individuals with significant disease that require a more comprehensive diagnostic exam. With our qualified vascular technologists and state-of-the-art ultrasound machines, we are able to non-invasively assess the arteries and categorize the degree of the disease using abbreviated and accurate protocols.