Deep vein thrombosis (DVT) definition and facts
- There are both superficial and deep veins in the limbs or extremities (arms and legs). A blood clot in the deep veins is a concern because it can cause life-threatening complications.
- A blood clot (thrombus) in the deep venous system of the leg becomes dangerous if a piece of the blood clot breaks off or travels through the blood stream, through the heart, and into the pulmonary arteries forming a pulmonary embolism. A person may not have signs or symptoms of a small pulmonary embolism (blood clot in the lungs), but a large embolism can be fatal.
- Risk factors for blood clot formation include immobility, a genetic tendency toward blood clotting, and injury to veins or adjacent tissues occurs.
- Symptoms of DVT or blood clot in the leg include:
- Redness of the leg or arm
- Doctors diagnose the condition is with blood tests, and then is confirmed by ultrasound or other imaging tests.
- Treatment of typically involves taking blood thinning medications (anticoagulants) unless you cannot take them (contraindicated). In that situation, an inferior vena cava filter is potentially considered.
- Complications of DVT include pulmonary embolism (PE) and post-phlebitic syndrome.
- There are other types of thrombosis such as:
- Cerebral venous thrombosis (CVT)
- Portal vein thrombosis
- Cavernous sinus thrombosis
What is DVT?
A deep vein thrombosis, or DVT describes a blood clot (thrombosis) that forms in the deep veins located in the arm or leg. It is important to know the body's anatomy and function to understand why clots form in veins and why they can be dangerous.
- Arteries have thin muscles within their walls to be able to withstand the pressure of the heart pumping blood to the far reaches of the body. Veins don't have a significant muscle lining, and there is nothing pumping blood back to the heart except physiology. Blood returns to the heart because the body's large muscles squeeze the veins as they contract in their normal activity of moving the body. The normal activities of moving the body returns the blood back to the heart. Being mobile causes this blood return system to fail, and the resulting stagnated blood may clot.
- There are two types of veins in the arm or leg; superficial veins and deep veins. Superficial veins lie just below the skin and are easily seen on the surface. Deep veins, as their name implies, are located deep within the muscles of the extremity. Blood flows from the superficial veins into the deep venous system through small perforator veins. Superficial and perforator veins have one-way valves within them that allow blood to flow only in the direction of the heart when the veins are squeezed.
- A blood clot (thrombus) in the deep venous system of the leg or arm, in itself, is not dangerous. It becomes potentially life-threatening when a piece of the blood clot breaks off and embolizes, travels through the circulation system through the heart, and enters into one of the pulmonary arteries and becomes lodged. This can prevent blood from flowing properly through the lung and decreasing the amount of oxygen absorbed and distributed back to the body.
- Diagnosis and treatment of a DVT is meant to prevent pulmonary embolism.
- Blood clots in the superficial veins do not pose a danger of causing pulmonary emboli because the perforator vein valves act as a sieve to prevent clots from entering the deep venous system. They are usually not at risk of causing pulmonary embolism.
What does a blood clot in the leg look like?
What causes DVT?
Blood is meant to flow. If it becomes stagnant, there is a potential for it to clot. The blood in veins constantly forms microscopic clots that are routinely broken down by the body. If the balance of clot formation and clot breakdown is altered, significant clotting may occur. A thrombus can form if one or a combination of the following situations.
- Prolonged travel and sitting, such as long airplane flights ("economy class syndrome"), car, or train travel
- Trauma to the lower leg with or without surgery or casting
- Pregnancy, including 6-8 weeks post-partum after delivery of the baby
Coagulation of the blood faster than usual (hypercoaguability)
Quick GuideDVT in Pictures: Symptoms of Deep Vein Thrombosis, Beyond Leg Pain and More
DVT Symptom: Leg Swelling
Leg swelling generally occurs because of an abnormal accumulation of fluid in the tissues of the lower extremity.
Symptoms that can be associated with leg swelling include:
- leg pain,
- redness, itching,
- shortness of breath, and
- ulceration of the skin.
Signs and symptoms of DVT
The signs and symptoms of DVT are related to obstruction of blood returning to the heart and causing a backup of blood in the leg. Classic symptoms include:
You may or may not have all of these symptoms, or your may have none. The symptoms of the condition may mimic an infection or cellulitis of the arm or leg.
In the past doctors and other health care professionals perform simple tests on patients to make a diagnosis of a blood clot in the leg; however, they have not been effective. For example, pulling the patient's toes toward the nose (Homans' sign), and squeezing the calf to produce pain (Pratt's sign). Today, doctors and health care professionals usually do not rely upon whether these signs and symptoms are present to make the diagnosis or decide that you have DVT.
Signs and symptoms of superficial blood clots
Blood clots in the superficial vein system (closer to the surface of the skin), most often occur due to trauma to the vein, which causes a small blood clot to form. Inflammation of the vein and surrounding skin causes the symptoms similar to any other type of inflammation, for example,
You often can feel the vein as a firm, thickened cord. There may be inflammation that follows the course of part of the leg vein. Although there is inflammation, there is no infection.
Varicosities can predispose to superficial thrombophlebitis and varicose veins. This occurs when the valves of the larger veins in the superficial system fail (the greater and lesser saphenous veins), which allows blood to back up and cause the veins to swell and become distorted or tortuous. The valves fail when veins lose their elasticity and stretch. This can be due to age, prolonged standing, obesity, pregnancy, and genetic factors.
Who is at risk?
There are a wide variety of people who are at risk for developing blood clots. Some risk factors include:
- Immobility, including prolonged bed rest due to illness or injury and long travel in a car or airplane
- Birth control pills or hormone therapy
- Surgery that damages the veins in an arm or leg
- Family history or genetic predisposition to forming blood clots
Which types of doctors treat DVT?
People with a swollen extremity or concern that a DVT exists may be cared for by a variety of health-care professionals. Both the primary care provider (including internal medicine and family medicine specialists) and a health care professional at in an urgent care (walk in) clinic or emergency department are able to recognize and diagnose the condition. Some people go to the hospital and the diagnosis is made there.
Treatment is usually started by the doctor who makes the diagnosis, but long-term treatment decisions, risk stratification, and follow-up usually is be done by the person's primary care doctor. Depending upon the situation, a hematologist (specialist in blood disorders) may be consulted. If there is need for the clot to be removed or dissolved, an interventional radiologist may also be involved.
Depending upon the medication used to anticoagulate the blood, pharmacists and anticoagulation nurses may also be involved on your treatment team.
What tests diagnose the condition?
The diagnosis of superficial thrombophlebitis usually is made by the doctor at the bedside of the patient, based upon history, potential risk factors present, and findings from the physical examination. Further risk stratification tools may include scoring systems that can help decide whether a DVT is likely.
If the probability of a leg thrombosis is low, a D-dimer blood test may be ordered.
- If the D-dimer is negative, then it is unlikely that a DVT is the diagnosis.
- If the D-dimer is elevated, then the possibility of a DVT exists and an imaging study, usually ultrasound, is required to look for the DVT
- Ultrasound is the standard method of diagnosing the presence of a deep vein thrombosis.
- The ultrasound technician may be able to determine whether a clot exists, where it is located in the leg or arm, and how large it is. It also may be possible to know whether the blood clot is new or chronic. If necessary, ultrasounds may be compared over time to see whether a clot has grown or resolved.
- Ultrasound is better at "seeing" the veins above the knee as compared to the small veins below the knee joint.
- Clots in the chest or pelvis may not be identified on ultrasound.
D-dimer is a blood test that may be used as a screening test to determine if a blood clot exists. D-dimer is a chemical that is produced when a blood clot in the body gradually dissolves. The test is used as a positive or negative indicator. If the result is negative, then in most cases no blood clot exists. If the D-dimer test is positive, it does not necessarily mean that a deep vein thrombosis is present since many situations will have an expected positive result. Any bruise or blood clot will result in a positive D-dimer result (for example, from surgery, a fall, in cancer or in pregnancy). For that reason, D-dimer testing must be used selectively.
- Venography, injecting dye into the veins to look for a thrombus, is not usually performed anymore and has become more of a historical footnote.
- Other blood testing may be considered based on the potential cause for the deep vein thrombosis.
What are the treatment guidelines for DVT?
The treatment for deep venous thrombosis is anticoagulation or "thinning the blood" with medications.
The recommended length of treatment for an uncomplicated DVT is three months. Depending upon the patient's situation, underlying medical conditions and the reason for developing a blood clot, a longer duration of anticoagulation may be required. At three months, the doctor or other health care professional should evaluate the patient in regard to the potential for future blood clot formation. If the decision is made to continue anticoagulation over the long term, the risk/reward decision of preventing clots versus bleeding risk should occur every year to decide if anticoagulation is still a reasonable treatment.
There are times when anticoagulation may have increased bleeding risk, for example, if the patient has had recent major surgery (anticoagulation thins all of the blood in the body not just the DVT). Other bleeding risks occur in patients with liver disease and those who take medications that can interact with the anticoagulation medicines.
What is the treatment of superficial blood clots?
Treatment for superficial thrombophlebitis treating the symptoms with:
- Warm compresses
- Leg compression
- Anti-inflammatory medications such as ibuprofen (Mortin) or naproxen (Naprocen).
If the thrombophlebitis occurs near the groin where the superficial and deep systems join together, there is potential that the thrombus could extend into the deep venous system. These patients may require anticoagulation or blood thinning therapy.
Medications to treat blood clots in the leg
Anticoagulation prevents further growth of the blood clot and prevents it from forming an embolus that can travel to the lung. The body has a complex mechanism to form blood clots to help repair blood vessel damage. There is a clotting cascade with numerous blood factors that have to be activated for a clot to form. There are difference types of medications that can be used for anticoagulation to treat DVT:
- Unfractionated heparin
- Low molecular weight heparin: enoxaparin (Lovenox)
- Novel oral anticoagulatants (NOACs) also known as direct oral anticoagulants (DOACs)
- Warfarin (Coumadin, Jantoven)
The American College of Chest Physicians has guidelines that give direction as to what medications might best be used in different situations. For example, a patient with a DVT, and no active cancer, treatment with a NOAC would be recommended. If active cancer exists, the treatment of DVT would be with enoxaparin as the drug of first choice.
NOACs work almost immediately to thin the blood and anticoagulate the patient. There is no need for blood tests to monitor dosing. The NOAC medications presently approved for deep vein thrombosis treatment include:
All four are also indicated to treat pulmonary embolism. They also may be prescribed to patients anticoagulated with nonvalvular atrial fibrillation to prevent stroke and systemic embolus.
Warfarin (Coumadin, Jantoven)
Warfarin (Coumadin, Janotven) is an anti-coagulation medication that acts as a Vitamin K antagonist, blocking blood clotting factors II, VII, IX and X. Historically, it was a first-line medication for treating blood clots, but its role has been diminished because of the availability of newer drugs. While warfarin may be prescribed immediately after the diagnosis of DVT, it takes up to a week or more for it to reach therapeutic levels in the blood so that the blood is appropriately thinned. Therefore, low molecular weight heparin (enoxaparin [Lovenox)] is administered at the same time. Enoxaparin thins the blood almost immediately and is used as a bridge therapy until the warfarin has taken effect. Enoxaparin injections can be given on an outpatient basis. For those patients who have contraindications to the use of enoxaparin (for example, kidney failure does not allow the drug to be appropriately metabolized), intravenous heparin can be used as the first step in association with warfarin. This requires admission to the hospital. The dosage of warfarin is monitored by blood tests measuring the prothrombin time (PT), or INR (international normalized ratio).
Side effects and risks of anticoagulation therapy
Patients who take anticoagulation medications are at risk for bleeding. The decision to use these medications must balance the risk and rewards of the treatment. Should bleeding occur, there are strategies available to reverse the anticoagulation effects.
Some patients may have contraindications to anticoagulation therapy, for example a patient with bleeding in the brain, major trauma, or recent significant surgery. An alternative may be to place a filter in the inferior vena cava (the major vein that collects blood from both legs) to prevent emboli, should they arise, from reaching the heart and lungs. These filters may be effective but have the potential risk of being the source of new clot formation. An IVC filter is NOT recommended for patients who are also taking anticoagulation medications.
Does DVT require surgery?
Surgery is a rare option in treating large deep venous thrombosis of the leg in patients who cannot take blood thinners or who have developed recurrent blood clots while on anti-coagulant medications. The surgery is usually accompanied by placing an IVC (inferior vena cava) filter to prevent future clots from embolizing to the lung.
Phlegmasia Cerulea Dolens describes a situation in which a blood clot forms in the iliac vein of the pelvis and the femoral vein of the leg, obstructing almost all blood return and compromising blood supply to the leg. In this case surgery may be considered to remove the clot, but the patient will also require anti-coagulant medications. Stents may also be required to keep a vein open and prevent clotting. May Thurner Syndrome, also known as iliac vein compression syndrome, is a cause of phlegmasia, in which the iliac vein in the pelvis is compressed and a stent is also needed.
What are the complications?
Pulmonary embolism is the major complication of deep vein thrombosis. With signs and symptoms such as chest pain and shortness of breath, it is a life-threatening condition. Most often pulmonary emboli arise from the legs.
Post-phlebitic syndrome can occur after a deep vein thrombosis. The affected leg or arm can become chronically swollen and painful with skin color changes and ulcer formation around the foot and ankle.
How can blood clots in the legs be prevented?
- Minimize risk factors for DVT, for example, quit smoking (especially if the person also is taking birth control pills or hormone therapy).
- In the hospital setting, the staff works hard to provide DVT prophylaxis to minimize the potential for clot formation in immobilized patients. Surgery patients are out of bed walking (ambulatory) earlier and low dose heparin or enoxaparin is being used for deep vein thrombosis prophylaxis (measures taken to prevent DVT).
- When traveling it is recommended that you get up and walk every couple of hours during a long trip.
Medically Reviewed on 7/3/2017
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