Deep Vein Thrombosis (DVT)

Formation of a thrombus (clot) in a vein that is embedded deep inside the flesh (deep vein) is termed as Deep Vein Thrombosis (DVT). This clot predominantly occurs in the deep veins present in the legs. Clot formation in the deep vein results in the occurrence of a vein blockage, termed as vascular occlusion. [1]

Technically speaking, terming the condition as "deep vein thrombosis" is a misnomer of sorts, as the term "thrombosis" refers to ANY kind of vascular blockage. [2] But in the case of DVT, blockage occurs specifically due to the occurrence of a clot within the vein.

Risk Factors for DVT

The risk factors for DVT are as follows - [3, 4]

• Previous history of DVT
• Cancer
• Injury or trauma
• Surgery
• Inheritable blood clotting
• Oral contraceptives
• Hormonal Replacement Therapy
• Sedentary lifestyle
• Long flights
• Smoking
• Pregnancy and the first six weeks after delivery

Symptoms of DVT

DVT may or may not show any symptoms. Symptoms are shown in only 50% subjects. Symptoms shown, if any, are as follows - [5, 6]

• Swelling and pain in the leg which occurs while standing or performing physical activity
• Skin of affected leg becomes warm and red as blood flow is diverted from the inner veins to the outer veins - occurrence of colour and temperature changes in the calf muscles of the leg
• Sensation of exhaustion and fatigue in leg
• Visible veins

If the clot resulting in vein blockage breaks apart, and affects one of the main arteries supplying oxygen to the lungs, this condition is called Pulmonary Embolism (PE), which requires immediate hospitalization. [7]

Therapies for DVT

The main goals of administering therapy for DVT are as follows - [8]
• Cessation of the increase of clot size
• Prevention of clot breakup and cessation of movement of clot towards the lungs
• Prevention of post-thrombotic syndrome, which can cause pain, swelling, and sores in the legs
• Reduction of chances of developing another blood clot

Some of the therapies administered for DVT are -

• Anticoagulants or blood thinners are drugs which prevent the clotting of blood. Effective therapy for prevention of blood clotting is the administration of anticoagulants such as heparin and warfarin. Heparin is administered intravenously (acts immediately) whereas Warfarin is administered orally (takes several days to act). Both are administered simultaneously. After Warfarin becomes effective, administration of Heparin is ceased. [9]

Two types of Heparin are administered -
♦ Unfractionated Heparin (UH), administered in hospital
♦ Fractionated Heparin (FH), self-administered at home

Warfarin is administered for a period of three months in cases of DVT in the upper legs. [8]

Pregnant women who suffer from DVT are administered only Heparin as consumption of Warfarin is dangerous during pregnancy.

Administration of blood thinners is carried out for a period of six months. However, the period of administration of therapy may change due to the following reasons - [9]
♦ Blood clot due to surgery, in which case, the treatment period will be relatively short
♦ Repeated blood clots can increase period of treatment
♦ Blood thinners administered for other conditions need to be continued till that particular illness is cured or treated completely.

• Thrombolytic treatments - If the blood clot cannot be reduced in size but needs to be dissolved instead, thrombolytic treatment ("Thrombolytic" = "Thrombus" + "Lysis" = Dissolution of clot) is administered through a catheter. [10] However, adequate care should be taken while administering thrombolytic treatment as there is a high but infrequent risk of intracranial bleeding as well as suffering from a stroke. [11]

• Vena cava filters - "Vena cava" is a large-sized vein present in the body. A filter is introduced in such a vein present in the abdomen. The function of this filter is to prevent broken clots from travelling from the legs to the lungs. In other words, this filter acts as a mechanical barrier so as to prevent further transport of the blood clot. [12]

These filters are conical in shape and resemble the wire spokes of an umbrella. They can be temporary or permanent in nature. [13] The main function of a vena cava filter is to trap blood clots, while allowing normal blood flow to occur through the vein.

Technique of filter insertion - [12]

Local anesthesia is administered in the groin. Ultrasound is used to introduce a needle into the target vein, and a wire having a diameter of 0.035 inches is passed into the inferior vena cava. Renal veins are studied with the help of a venogram, and the diameter of the vena cava is measured for inserting the filter of the correct size.

However, these filters do not prevent the formation of newer blood clots.

• Surgery (Thrombectomy) - Thrombus or blood clot can be removed through surgery. This is called thrombectomy (surgical removal of a vascular blood clot or thrombus). This is carried out in cases of excessive clotting. [14]

The most important aspect of carrying out a thrombectomy is to find out the precise location of the clot and the extent to which clotting has taken place, for which techniques such as ultrasonography and venogram are used. [14]

• Graduated Compression Stockings - These stockings can be worn from the toes to the knees. These stockings help in the reduction of swelling, pain, and ulceration caused due to blood clots. They also help in the prevention of post-thrombotic syndrome. [9]

Stockings should be worn for at least three years after suffering from DVT as post-thrombotic symptoms can last for months or even years. [9]

• Physical activity - One of the main reasons for suffering from DVT is lack of physical activity, sedentary lifestyle, as well as long flight hours and long travelling time (without proper leg movement) which increases pressure on the calf muscles. Increasing levels of physical activity controls the symptoms of DVT such as pain and swelling. Raising the leg during periods of sedentary activity or rest decreases the pressure on the calf muscle and decreases stress on the vascular tissues in the legs. [9]

The leg should be raised at such a level that it is higher than the level of the hip. Also, a cushion can be used so that raising the leg at a higher level than the hip becomes an easy task. [9]


References
1. http://en.wikipedia.org/wiki/Deep_vein_thrombosis
2. http://en.wikipedia.org/wiki/Vascular_occlusion
3. http://www.mayoclinic.com/health/deep-vein-thrombosis/DS01005/DSECTION=risk-factors
4. http://www.webmd.com/dvt/deep-vein-thrombosis-causes-are-you-at-risk-for-dvt
5. http://www.webmd.com/dvt/deep-vein-thrombosis-dvt-symptoms-diagnosis
6. http://www.patient.co.uk/health/deep-vein-thrombosis-leaflet
7. http://www.webmd.com/dvt/deep-vein-thrombosis-pulmonary-embolism
8. http://www.webmd.com/dvt/tc/deep-vein-thrombosis-treatment-overview
9. http://www.nhs.uk/Conditions/Deep-vein-thrombosis/Pages/Treatment.aspx
10. http://www.mayoclinic.com/health/deep-vein-thrombosis/DS01005/DSECTION=treatments-and-drugs
11. http://emedicine.medscape.com/article/1911303-treatment#aw2aab6b6b8
12. http://emedicine.medscape.com/article/1911303-treatment#aw2aab6b6c11
13. http://www.mayoclinic.com/health/deep-vein-thrombosis/DS01005/DSECTION=treatments-and-drugs
14. http://emedicine.medscape.com/article/1911303-treatment#aw2aab6b6c10

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