Deep Vein Thrombosis (DVT)

Veins may be damaged during surgery or during an injury to an arm or leg, by the injection of irritating substances, by inflammation, or by certain disorders, such as thromboangiitis obliterans Thromboangiitis Obliterans Thromboangiitis obliterans is inflammation and subsequent blockage of small and medium-sized arteries of the legs or arms. Thromboangiitis obliterans commonly develops in smokers. Symptoms are... read more . They may also be injured by a clot, making formation of a second clot more likely.

Some disorders, such as cancer and certain inherited disorders of blood clotting Overview of Blood Clotting Disorders Blood clots help stop bleeding. Blood clotting (coagulation) disorders are dysfunctions in the body's ability to control the formation of blood clots. These dysfunctions may result in Too little... read more , cause blood to clot when it should not. Some drugs, including oral contraceptives, estrogen therapy, or drugs that act like estrogen (such as tamoxifen and raloxifene), can cause blood to clot more readily. Smoking is also a risk factor. Sometimes blood clots more readily after childbirth or surgery. Among older people, dehydration commonly causes the blood to clot more readily and can therefore contribute to deep vein thrombosis.

During prolonged bed rest and other occasions when the legs are not moving normally (such as after a leg injury or a stroke), blood flow slows because the person is lying down and the calf muscles are not contracting and squeezing the blood toward the heart. For example, deep vein thrombosis may develop in people who have had a heart attack Acute Coronary Syndromes (Heart Attack; Myocardial Infarction; Unstable Angina) Acute coronary syndromes result from a sudden blockage in a coronary artery. This blockage causes unstable angina or a heart attack (myocardial infarction), depending on the location and amount... read more or other serious disorder (such as heart failure Heart Failure (HF) Heart failure is a disorder in which the heart is unable to keep up with the demands of the body, leading to reduced blood flow, back-up (congestion) of blood in the veins and lungs, and/or... read more , chronic obstructive pulmonary disease Chronic Obstructive Pulmonary Disease (COPD) Chronic obstructive pulmonary disease is persistent narrowing (blocking, or obstruction) of the airways occurring with emphysema, chronic obstructive bronchitis, or both disorders. Cigarette... read more [COPD], or a stroke Overview of Stroke A stroke occurs when an artery to the brain becomes blocked or ruptures, resulting in death of an area of brain tissue due to loss of its blood supply (cerebral infarction). Symptoms occur suddenly... read more ) and lie in a hospital bed for several days without sufficiently moving their legs or in people whose legs and lower body are paralyzed (paraplegics). Deep vein thrombosis can develop after major surgery, particularly pelvic, hip, or knee surgery. Thrombosis can even occur in healthy people who sit for long periods, for example, during long drives or airplane flights, but thrombosis is extremely uncommon in this circumstance and usually occurs in people with other risk factors.

In people who have deep vein thrombosis, a blood clot may break loose from an affected vein in the leg. A clot that breaks loose is called an embolus. The embolus can travel through the bloodstream, through the heart, and into the lungs, where it lodges in a blood vessel in the lung, blocking blood flow to a portion of the lung. This blockage is called pulmonary embolism Pulmonary Embolism (PE) Pulmonary embolism is the blocking of an artery of the lung (pulmonary artery) by a collection of solid material brought through the bloodstream (embolus)—usually a blood clot (thrombus) or... read more and can be fatal, depending on how large the embolus is and the size of the blocked lung artery. The small blood clots that occur in superficial venous thrombosis usually do not become emboli. Thus, only thrombi in the deep veins are potentially dangerous.

Blood clots in the legs or pelvis are more likely to become emboli than blood clots in the arms, perhaps because the squeezing action of the calf muscles can dislodge a blood clot in a deep vein.

The consequences of pulmonary embolism depend on the size and number of emboli:

Massive emboli are not common, but no one can predict which case of deep vein thrombosis, if untreated, will lead to a massive embolus.

Multiple emboli may occur. Multiple emboli typically go to different parts of the lungs.

Sometimes, people have an abnormal opening, called a patent foramen ovale Normal Fetal Circulation About one in 100 babies is born with a heart defect. Some are severe, but many are not. Defects may involve abnormal formation of the heart's walls or valves or of the blood vessels that enter... read more , between the right and left upper chambers of the heart (the atria). If this opening is present, an embolus can pass into the arterial circulation and block an artery in another part of the body, such as the brain where it will cause a stroke Ischemic Stroke An ischemic stroke is death of an area of brain tissue (cerebral infarction) resulting from an inadequate supply of blood and oxygen to the brain due to blockage of an artery. Ischemic stroke... read more .

Some blood clots heal by being converted to scar tissue, which may damage the valves in the veins. The damaged valves prevent the veins from functioning normally, a disorder called chronic venous insufficiency Chronic Venous Insufficiency and Postphlebitic Syndrome Chronic venous insufficiency is damage to leg veins that prevents blood from flowing normally. Postphlebitic syndrome is chronic venous insufficiency that results from a blood clot in the veins... read more or postphlebitic syndrome Chronic Venous Insufficiency and Postphlebitic Syndrome Chronic venous insufficiency is damage to leg veins that prevents blood from flowing normally. Postphlebitic syndrome is chronic venous insufficiency that results from a blood clot in the veins... read more . In this disorder, fluid accumulates (a condition called edema) and the ankle and sometimes lower leg swells. The skin can become scaly, itchy, and reddish brown.

Rarely, a very large blood clot in a leg causes so much swelling that it blocks the blood flow through the leg. The leg becomes pale or blue and extremely painful. Gangrene can develop if the blood flow is not restored.

Anticoagulant drugs are blood thinners. They decrease the blood’s ability to clot, so they can prevent new clots from forming and can stop existing clots from getting bigger. They do not break up or dissolve clots that have already formed. All people with deep venous thrombosis are given anticoagulant drugs.

Doctors usually use low-molecular-weight heparin (such as enoxaparin, dalteparin, or tinzaparin) or fondaparinux given by injection under the skin (subcutaneously), accompanied by warfarin taken by mouth. The injectable drug works immediately, but warfarin takes several days to be fully effective. Once the warfarin has taken effect, people stop taking the injectable drug. For some people (those with cancer or those with recurrent clotting problems despite treatment with anticoagulants by mouth), doctors only use the injectable drug and do not start warfarin.

How long people continue drug treatment (with warfarin or an injectable drug) varies according to the degree of risk. People whose deep vein thrombosis resulted from a specific, temporary cause (such as surgery or a drug they have stopped taking) usually continue drug treatment for 3 to 6 months. When a specific cause is not found, people usually take warfarin for at least 6 months. Warfarin should be continued indefinitely if the cause is not temporary (for example, a blood clotting disorder) or if people have had two or more episodes of deep vein thrombosis.

Use of warfarin increases the risk of bleeding, both internally and externally. To minimize the risk, people taking warfarin must have periodic blood tests to see how much their blood is anticoagulated. Doctors then use the blood test result to adjust the dose of warfarin. The blood tests are usually done once or twice a week for 1 or 2 months, and then every 4 to 6 weeks thereafter.

Many different drugs and foods change how the body breaks down warfarin (see also Drug Interactions Drug Interactions The effect a drug has on a person may be different than expected because that drug interacts with Another drug the person is taking (drug-drug interaction) Food, beverages, or supplements the... read more ). Some drugs and foods increase its breakdown, making a warfarin dose less effective and increasing the risk of another blood clot. Other drugs and foods slowwarfarin's breakdown, making a dose more effective but also more likely to cause bleeding. Some people are also more sensitive to warfarin and may need warfarin-sensitivity testing to help doctors adjust their levels.

Direct oral anticoagulants (DOAC) are an alternative to warfarin. Rivaroxaban, apixaban, edoxaban, and dabigatran are DOACs. These drugs have a faster anticoagulant effect than warfarin and are as effective as warfarin for the treatment of blood clots. The effect of DOACs on people's blood is more predictable than the effect of warfarin. Therefore, unlike people taking warfarin, people taking DOACs do not need to have frequent blood tests to adjust the dose. Also, DOACs tend to cause fewer episodes of serious bleeding than warfarin. However, bleeding caused by DOACs can be harder to stop because antidotes for these drugs are not as widely available as antidotes for warfarin.

Excessive bleeding, which may be life-threatening, is the most common complication of anticoagulant drugs. Risk factors for excessive bleeding include being age 65 or older or having

For people who are taking warfarin, doctors can give vitamin K, transfusions of plasma (which contains clotting factors), or prothrombin complex concentrate to reverse the effects of the warfarin and stop the bleeding. For people who are taking heparin, doctors can give protamine to partially reverse the effects.

For people taking some of the DOACs, doctors can give andexanet alfa or prothrombin complex concentrate to reverse the effects of the DOACs and stop the bleeding.

Very rarely, as an alternative to anticoagulant drugs Anticoagulant drugs Deep vein thrombosis is the formation of blood clots (thrombi) in the deep veins, usually in the legs. Blood clots may form in veins if the vein is injured, a disorder causes the blood to clot... read more , doctors place a filter (formerly called an umbrella) inside a large vein between the heart and the area affected by deep vein thrombosis, such as the inferior vena cava. The inferior vena cava is a large vein that returns blood to the heart from the lower part of the body. The filter can trap emboli, preventing them from reaching the lungs.

However, unlike anticoagulant drugs Anticoagulant drugs Deep vein thrombosis is the formation of blood clots (thrombi) in the deep veins, usually in the legs. Blood clots may form in veins if the vein is injured, a disorder causes the blood to clot... read more , filters do not prevent new clots from forming. Filters are usually reserved for people in whom anticoagulant therapy is not possible or not effective.

Doctors only occasionally use intravenous drugs, such as alteplase, to dissolve venous blood clots. These drugs (also called thrombolytic, fibrinolytic, or clot-busting drugs) may be given to a person with extensive blood clots if the blood clot has been present for less than 48 hours and the person does not have risk factors for excessive bleeding. After 48 hours, scar tissue begins to develop in the blood clot, making it less likely to dissolve. Clot-dissolving drugs have a higher risk of bleeding complications.

Doctors sometimes use clot-dissolving drugs in combination with mechanical removal methods in people who have large clots in their upper leg. In such cases, doctors may put a small, flexible tube (catheter) into the blocked vein, remove as much clot as possible with an instrument, and administer the clot-dissolving drug through the catheter.

If pulmonary embolism Treatment Pulmonary embolism is the blocking of an artery of the lung (pulmonary artery) by a collection of solid material brought through the bloodstream (embolus)—usually a blood clot (thrombus) or... read more occurs, treatment usually includes oxygen (usually given by a face mask or nasal prongs), analgesics to relieve pain, and anticoagulant drugs Anticoagulant drugs Deep vein thrombosis is the formation of blood clots (thrombi) in the deep veins, usually in the legs. Blood clots may form in veins if the vein is injured, a disorder causes the blood to clot... read more . If pulmonary embolism is life threatening, clot-dissolving drugs are given or surgery is done to remove the embolus.

The veins never completely recover after deep vein thrombosis develops. Elastic compression stockings worn below the knee may be helpful if chronic venous insufficiency Chronic Venous Insufficiency and Postphlebitic Syndrome Chronic venous insufficiency is damage to leg veins that prevents blood from flowing normally. Postphlebitic syndrome is chronic venous insufficiency that results from a blood clot in the veins... read more develops.

If painful skin ulcers (venous stasis ulcers Chronic Venous Insufficiency and Postphlebitic Syndrome Chronic venous insufficiency is damage to leg veins that prevents blood from flowing normally. Postphlebitic syndrome is chronic venous insufficiency that results from a blood clot in the veins... read more ) develop, properly applied compression bandages can help. When these bandages are applied carefully once or twice a week, the ulcer almost always heals because blood flow in the veins improves. The ulcers can become are infected, and pus and a foul-smelling discharge can appear on the bandage each time it is changed. The pus and discharge can be washed off the skin with soap and water. Skin creams, balms, and skin medications of any kind have little effect.

Once blood flow in the veins has improved, the ulcer heals by itself. After it has healed, wearing an elastic stocking daily can prevent a recurrence. The stocking must be replaced as soon as it becomes too loose. If possible, the person should purchase seven stockings or pairs of stockings (if both legs are involved)—one for each day of the week so that stockings remain effective considerably longer.

Rarely, ulcers that do not heal require skin grafting. After grafting, an elastic stocking must be worn to prevent ulcers from returning.