Deep Vein Thrombosis is a common disorder relating to the formation of blood clots in major veins. It can affect people of any age but the risk of developing a DVT increases after the age of 40 years. DVT has been linked in recent years with long distance air travel.
Life-threatening complications can arise from DVT when blood clots dislodge, travelling through the body and lodging in other veins or arteries, forming an embolism. This can be life threatening, especially when the embolism occurs in the lungs, heart or brain. Pulmonary embolism (a blood clot in the lung) is the most common of these serious DVT complications.
Veins are blood vessels that carry blood from the tissues of the body back to the heart. Veins that lie just beneath the skin surface are referred to as “superficial veins” while veins found deep inside the muscles are referred to as “deep veins”. Other veins connect the superficial and deep veins, allowing blood to flow between them.
When a blood clot occurs in a vein it is referred to as a venous thrombosis. A deep vein thrombosis (DVT) is a blood clot that occurs in the deep veins. DVTs can occur in any of the deep veins but most commonly occur in the leg and pelvic veins. The clot will either partially or completely block the flow of blood through the affected vein. When the blood clot is associated with inflammation of the vein it is referred to as thrombophlebitis.
A DVT is usually more serious than a blood clot in one of the superficial veins, as there is a much greater risk that part of the clot may dislodge and circulate through the body.
A DVT is more likely to occur when the blood flow through the deep veins is slowed or where there is some factor that makes the blood more likely to clot.
General factors that increase the risk of developing a DVT include:
Factors that can slow the blood flow include:
Factors that can make the blood more likely to clot:
A DVT does not always cause symptoms. If symptoms do occur the first symptom is usually a cramp-like aching pain – often in the calf muscles. This pain might worsen when walking but does not subside with rest. Other symptoms of a DVT may include:
If a pulmonary embolism occurs it can produce very mild, barely noticeable symptoms such as mild chest discomfort and mild breathlessness. However it can also produce more noticeable symptoms such as sharp chest pain, a rapid heart rate, breathlessness and coughing up blood. As a pulmonary embolism is a serious situation that requires prompt medical treatment, it is important to seek urgent medical attention even if only mild symptoms are experienced.
If a DVT is suspected, it is important to seek medical attention promptly. Accurate diagnosis and appropriate treatment are required to reduce the risk of complications such as pulmonary embolism.
Because a DVT can occur without any obvious symptoms, diagnosis can sometimes be difficult. Initially the doctor will examine the affected area, take a full medical history and may recommend a blood test called a D-Dimer. This test measures a breakdown substance of fibrinogen (a protein essential for blood clotting). If the D-Dimer test is negative, the patient is unlikely to have a DVT. If the test is positive, further tests to confirm the diagnosis are likely to be ordered.
One of the most common diagnostic tests for DVT is an ultrasound scan. The type of scan used is called a Doppler ultrasound. The scan is painless and is able to detect up to 95% of DVTs.
If there is doubt about the diagnosis, venography may be recommended. This diagnostic test involves injecting a specialised dye into the veins. This dye can be seen by x-ray as it flows through the veins, allowing them to be easily visualised.
Other tests that may be used to assist with diagnosis include:
If a pulmonary embolism is suspected, a VQ scan may be recommended. During this scan the patient inhales a special aerosol and a special dye is injected into a vein (intravenously). The aerosol and dye can be seen on x-ray as they move through the lungs. A series of x-rays are then taken which assess the flow of blood and air through the lungs. Abnormalities may suggest a pulmonary embolism.
Specialised CT scans or pulmonary angiography (where dye is injected into the arteries of the lungs through a long catheter threaded up to the heart via a vein in the groin) may also be used to diagnose a pulmonary embolism.
The immediate goal of treatment is to prevent complications and to limit the size of the clot and its movement. Treatment will depend on the location and severity of the clot. Some small clots may resolve spontaneously without treatment, however a DVT is generally treated intensively. Usually the person is admitted to hospital for treatment and observation for signs of complications. Treatment may include:
These medications “thin” the blood, reducing its ability to clot. Anticoagulant medications can be administered as a continuous infusion into a vein (intravenously), as an injection under the skin (subcutaneously), or in tablet form. Blood tests to monitor their effectiveness are required regularly and dosage changes may be required.
On admission to hospital it has been common to be give an intravenous anticoagulant called heparin, which acts quickly to thin the blood. At the same time an anticoagulant tablet called warfarin is also given. The warfarin is slow acting and can take several days to become effective. Once the warfarin tablets becomes effective, the intravenous heparin is stopped.
Anticoagulant treatment, in the form of tablets or heparin injections, needs to be maintained for at least three months to be fully effective in treating a DVT. In some cases it may be required on a long-term basis.
In some cases these medications are given to help dissolve the clot. They are given intravenously, however they can cause side effects such as severe bleeding. Because of this, they are usually only used in life-threatening situations, such as the presence of a large pulmonary embolus.
These graded, elasticised compression stockings give support to the lower legs. This encourages the return of blood to the heart and helps to reduce swelling. It is generally recommended that compression stockings are worn in situations where immobility is likely.
Deep vein thrombosis (DVT) is the formation of a blood clot, known as a thrombus, in the deep leg vein. It is a very serious condition that can cause permanent damage to the leg, known as post-thrombotic syndrome, or a life-threating pulomnary embolism. In the United States alone, 600,000 new cases are diagnosed each year. One in every 100 people who develops DVT dies. Recently, it has been referred to as “Economy Class Syndrome” due to the occurrence after sitting on long flights.
The deep veins that lie near the center of the leg are surrounded by powerful muscles that contract and force deoxygenated blood back to the lungs and heart. One-way valves prevent the back-flow of blood between the contractions. (Blood is squeezed up the leg against gravity and the valves prevent it from flowing back to our feet.) When the circulation of the blood slows down due to illness, injury or inactivity, blood can accumulate or “pool,” which provides an ideal setting for clot formation.
Post-thrombotic syndrome is an under-recognized, but relatively common sequela, or aftereffect, of having DVT if treated with blood thinners (anticoagulation) alone, because the clot remains in the leg. Contrary to popular belief, anticoagulants do not actively dissolve the clot, they just prevent new clots from forming. The body will eventually dissolve a clot, but often the vein becomes damaged in the meantime. A significant proportion of these patients develop permanent irreversible damage in the affected leg veins and their valves, resulting in abnormal pooling of blood in the leg, chronic leg pain, fatigue, swelling, and, in extreme cases, severe skin ulcers. While this use to be considered an unusual, long-term sequela, it actually occurs frequently, in as many as 60-70 percent of people, and can develop within two months of developing DVT. There is increasing evidence that clot removal via interventional catheter-directed thrombolysis in selected cases of DVT can improve quality of life and prevent the debilitating sequela of post-thrombotic syndrome.
Left untreated, a deep vein thrombosis (DVT) can break off and travel in the circulation, getting trapped in the lung, where it blocks the oxygen supply, causing heart failure. This is known as a pulmonary embolism, which can be fatal. With early treatment, people with DVT can reduce their chances of developing a life threatening pulmonary embolism to less than one percent. Blood thinners like heparin and coumadin are effective in preventing further clotting and can prevent a pulmonary embolism from occurring.
The symptoms are frequently nonspecific and can mimic many other cardiopulmonary events.