What is Deep vein thrombosis (DVT)
Deep vein thrombosis (DVT) is a condition where there is the development of clots (thrombus) in the deep veins of the body, most commonly in the deep veins of the legs.
DVT causes symptoms of leg pain or swelling but can happen in a silent manner without causing any symptoms.
It is a serious condition because the blood clot in the vein can dislodge from where it had formed and travel through the bloodstream to the heart and then to the lungs, blocking the blood flow to the lungs (called as pulmonary embolism).
Causes and risk factors
Normally blood flow is smooth in the deep veins and the blood does not clot. For blood to clot, there should be a predisposing factor or a factor that prevents the blood from flowing smoothly.
Multiple factors are known to increase the risk of DVT such as:
- Prolonged bed rest or immobility: When the legs are immobile for a long duration, such as in those who are bedridden for a long time for any reason there is less contraction in calf muscles and blood remains stationary in the vein.
- Sitting for long duration such as in long drive or long flight: when the legs are at rest for a long duration, blood is not pumped for a long duration.
- Genetic predisposition to blood-clotting: Some people have inherited disorders that make them highly predisposed to blood clotting.
- Previous history of DVT or family member with DVT or pulmonary embolism (PE): These conditions increase the risk of DVT.
- Age: Though DVT can happen at any age, elderly people over the age of 60 years are at higher risk.
- Trauma or surgery: Any injury, fractures, or surgery that breaks the continuity of the blood vessels can increase the possibility of blood clotting.
- Overweight and obesity: Considered to be due to increased pressure in the veins of the pelvis and legs.
- Smoking: The particles contained in the smoke are known to increase the risk of blood clotting.
- Pregnancy: The uterus (womb) with the growing baby can put pressure on the veins in the pelvis, which can slow the upward flow of the blood in the legs and increase the risk of DVT, especially in women who are already predisposed to clotting.
- Oral contraceptive pills and hormone replacement medicines: Hormones contained in these medications can increase the blood’s ability to clot.
- Heart failure: In heart failure, the pumping function of the heart is decreased, and there is a higher risk of DVT.
- Inflammatory bowel diseases: Crohn’s disease and ulcerative colitis have shown an association with DVT, suggesting an increased risk of DVT in these conditions.
- Cancer: Cancer cells can activate the blood clotting system and increase the ability of blood to clot.
Symptoms and signs
Deep vein thrombosis mostly presents with:
- Pain in the leg: The pain is felt mainly in the calf region. Sometimes the entire area around the affected vein can have pain. The pain may feel more when the foot is raised upwards towards the knee.
- Leg swelling: As the blood flow is blocked in the affected leg, fluids collect in that limb causing swelling of the leg.
- Redness and warmth: The affected area may become red and feel warm to touch.
In some individuals, DVT can cause no symptoms and remain silent. It may be detected incidentally, during some scan or imaging.
- History and physical examination: Medical history and swelling, colour change and tenderness of the affected limb on physical examination indicate DVT
- Ultrasound: A probe that transmits ultrasound is placed on the skin over the affected area to visualise the underlying structures on a TV monitor. The scan may show a clot in the affected vein. If the scan shows a clot, then this test may be repeated to see if the size of the clot is growing or reducing, and to look for development of new clots.
- CT or MRI scans: These scans show the images of the vein and can pick up the presence of clots.
- Venogram: A special dye injected into a vein in the foot moves upwards and creates an image of the vein when an X-ray is taken. Blocked areas in the vein can be observed when the DVT is present.
- D-Dimer Blood test: D-dimer is a clot-dissolving particle seen in the blood of those who have severe DVT. A positive test for D-dimer suggests that the person may have a DVT; however, there can be a positive test from any injury, surgery or inflammation in the body. Positive tests have to be confirmed by other tests and scans. A negative test for D-dimer can rule out DVT with almost 97% certainty.
Treatment and prevention
The aim of the treatment is to stop the clot from getting big and preventing it from getting dislodged from the vein and thus preventing pulmonary embolism. The next stage is preventing DVT from occurring again.
Anticoagulants (Blood thinners): These medicines reduce the ability of blood to clot. They do not break the already formed clot, but only prevent the existing clot from getting bigger, and reduce the risk for new clot formation.
Initially, an injection of blood thinner namely heparin may be given, followed by another blood thinner injection such as enoxaparin, dalteparin or fondaparinux. Some blood thinners are also given as pills, such as warfarin or rivaroxaban.
The blood thinners may be continued for few months. Periodic tests may be done when individuals are on these medicines to check for the bleeding and clotting times.
Thrombolytic agents (Clot busters): Medications called thrombolytics (clot busters) may be prescribed for severe DVT or pulmonary embolism cases, or if other medications are not working. They are given in hospitals through a catheter inserted into the clot.
Compression stockings: These are the socks like garments worn on the leg having DVT, which function to compress the limb. The pressure of the stocking reduces the chances of blood pooling and clotting and provides relief from swelling seen in DVT.
Filters: In individuals for whom the anticoagulant treatment is not suitable or needs to be stopped, a filter may be inserted into the big vein (inferior venacava) in the abdomen as a precautionary measure against pulmonary embolism. This prevents any broken clots from going into the lungs and causing pulmonary embolism.
Some of the common preventive measures for DVT include:
Avoid prolonged sitting
If you are in bed rest after surgery or for some other reasons, try to resume walking as soon as possible. While in bed rest, if possible move your foot up and down to pump the calf muscles periodically.
If you are driving for a long duration, stop periodically and walk around a little.
If you are on a plane, try to stand and walk as frequently as possible. If that is not possible, try to exercise your lower limbs (raise toes with heel on the floor and raise heel with toes on the floor).
DVT prophylaxis: In some orthopaedic surgeries and in some patients before having any surgery that requires extended bed rest, blood thinners may be given to prevent clotting.
Reduce weight and make lifestyle changes: Losing weight, exercising and smoking cessation may reduce the chances of clotting in those who are predisposed, those who have to sit for a prolonged duration or in those who travel frequently.
Pulmonary embolism: In this condition, a clot formed in another part of the body, most frequently the leg, travels into and blocks a blood vessel in the lung. This condition is dangerous and can result in death in some cases.
A person with DVT should be aware of its symptoms and alert their doctor if they experience a sudden onset of breathlessness, chest pain, light-headedness or dizziness, fainting, rapid heart beats and coughing up blood.
Post-phlebitic syndrome: DVT damages the veins in the leg and reduces the blood flow in the affected regions causing this syndrome. The symptoms of this condition include leg swelling, leg pain, discoloration of the skin, and skin sores.
If you develop symptoms and signs of DVT, contact your doctor as early as possible.
If you develop symptoms of pulmonary embolism, contact your doctor immediately. These include:
- Sudden onset breathlessness
- Chest discomfort or pain that increases when you cough or take a deep breath
- Dizziness or lightheadedness or fainting
- Fast heart beat
- Coughing up blood
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- NHS choices. Deep vein thrombosis. Accessed at http://www.nhs.uk/Conditions/Deep-vein-thrombosis/Pages/Introduction.aspx
- Medline Plus. Deep vein thrombosis. Accessed at https://www.nlm.nih.gov/medlineplus/ency/article/000156.htm
- Deep vein thrombosis. National Heart, Lung, and Blood Institute. http://www.nhlbi.nih.gov/health/health-topics/topics/dvt/.
- DVT/PE Facts. Centers for Disease Control and Prevention. http://www.cdc.gov/ncbddd/dvt/facts.html.