Deep Venous Thrombosis (DVT)

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Full Name: Kannivelu Badrinath
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Deep Venous Thrombosis (DVT)

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You may not have worried about “DVT” in the past, yet this common medical condition affects nearly 2 million people in USA every year and many die from resulting pulmonary embolism. DVT stands for deep venous thrombosis. It occurs when blood clots in a vein, often in a deep vein of the leg. Today with frequent air travel public are becoming aware of it.

Normally blood flows freely through veins. When the flow is interrupted either by injury or by compression of the vein, it slows or stops beyond the point of compression. When this happens blood in the vein can clot. When the clot breaks off and travels to the lung, pulmonary embolism results with breathlessness or chest pain. If the clot is large enough it can prove fatal.

People at Risk of DVT:
• Following any major surgery particularly involving the hip, knee or leg
• Patients on plaster casts of the leg following fractures
• Patients recovering from major surgery and confined to bed
• Elderly or any individual who is bedridden for prolonged periods
• Women on contraceptive Pills
• Pregnancy and childbirth
• Varicose veins
• Passengers confined to their seats on long haul flights

Generally the older you are the greater the chances of developing DVT. It is said that the chances double with each decade of life after 40.

The reason for developing DVT during long haul flight is because the passenger may be confined to a cramped seat for prolonged periods with the knee bent and with some pressure on the calf muscles. When the legs are not moved, the continuous pressure can result in blood stagnating in the vein giving rise to clot formation.

A woman on any contraceptive pill containing oestrogen has a 1 in 1000 chance of developing a DVT. Similarly during prgnancy and soon after delivery when the oestrogen levels are high the woman may be prone to DVT.

DVT can cause pain and swelling in the leg. Occasionally there may be no symptom from the leg but the individual may present with chest pain and shortness of breath from pulmonary embolism (PE) caused by the clot moving to the lung.

• Swollen leg compared to opposite leg
• Leg may be warm and red
• Pain in the calf muscle particularly when pressure is applied
• Sudden onset of chest pain or difficulty to breathe may be from pulmonary embolism.

Diagnosing DVT:
Clinical examination may suggest possible DVT. This should be confirmed by one or two tests.

• Ultrasound: US will usually confirm a blocked vein from a clot.
• D-dimer test: If the level of D-Dimer is raised, it is probable that you have DVT.
• Venography: Venography is usually done if the ultra sound is not very clear.
• Sometimes MRI or CT scan may be requested.
• If pulmonary embolism is suspected a Ventilation/Perfusion scan is done.

D-Dimer test: Anyone who develops a significant DVT will have an elevated clot-dissolving substance called D-dimer in the blood. D-dimer is a fibrin degradation product (or FDP) after the clot is degraded by fibrinolysis. It is so named because it contains two crosslinked D fragments of the fibrin protein.

Venograph: A dye (contrast agent) is injected into a large vein in the foot or ankle. An X-ray of the leg then shows obstruction in the vein.

CT or MRI scans: CT and MRI scans can show visual images of the veins and any clot in them. However, the scans are rarely needed as the simpler tests can confirm the diagnosis.

Preventing DVT:
Steps should be taken to prevent a DVT rather than worry about it when it happens. It is now routine practice to prescribe an anticoagulant when patients are subjected to major lower limb surgery. They are maintained on the anticoagulant therapy until they start walking and become more active.

In good operating theatres an intermittent calf compression device is used when a patient has any procedure done under a general anesthetic.

Most patients who are admitted to hospital are also given anti embolism stockings to wear. These are elastic stockings that provide uniform compression for the leg preventing pooling of blood in the veins when they are in bed.

Older age group people must be encouraged to exercise regularly and advised to avoid sitting or lying in bed for prolonged periods.

Long distance travellers, be it on a plane, train or bus must be encouraged to exercise every hour. They should be advised if possible to get out of their seat and walk in the aisle from time to time. If they are unable to do that, the least they can do is dorsiflex and plantarflex the foot constantly. They can also wear compression stockings that can be purchased in a travel store or a chemist.

All these measures are particularly important for individuals who have had a DVT in the past or have a higher risk of developing DVT.

The main goal of treating a DVT is to stop a clot from increasing in size and to stop it getting to the lung.

Anti Coagulants: Medication used in DVT is either administered through the needle or through a tablet. They are collectively termed anticoagulants. They act by turning off or delaying the clotting mechanism in the body. Heparin and Warfarin are the two main drugs used in DVT. Heparin is given subcutaneously by the needle and warfarin as a pill. Heparin can also be given intravenously. There are different types of heparin. Coumadin is a common brand name for warfarin.

Once DVT is suspected and diagnosed, treatment is started promptly with heparin and warfarin. The heparin or low molecular weight heparin is continued with the warfarin for at least 5 days. This is because the action of heparin is instant, whereas warfarin takes 3 to 5 days before the anticoagulant effect becomes stable. Stability is decided by checking the PT (prothrombin time) expressed as INR. The INR is maintained between 2 to 5. There is a risk of internal bleeding if the INR is too high. The heparin or low molecular weight heparin should not be stopped until the patient's INR is in a stable range..

The length of time that a patient will need to take warfarin will depend on the cause of DVT. If it follows surgery or trauma they should be on the anticoagulant for about 3 months. If the clot was caused by a chronic condition treatment may be continued for 6 to 12 months.

Anti-coagulants cannot get rid of blood clots. They can only prevent a clot getting bigger or new clots from forming. Given the time the clot will dissolve on its own by the body’s own chemical mechanism. Drugs called thrombolytics are sometimes used to dissolve a DVT. These are used only in critical conditions where there is a risk of losing a limb or life. They should be used with caution as they can cause serious bleeding.

Anyone who suddenly develops leg pain and swelling or breathing problems within a week after being in a hospital or been on a long haul flight should seek medical advice immediately.

Complication following DVT: Following DVT one of the complications is chronic swelling or oedema of the leg caused by venous insufficiency. Treatment of this condition may be difficult and prolonged with physiotherapy, wearing supportive stocking permanently etc. The clinical name for the condition is post-thrombotic syndrome
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