Deep vein thrombosis (DVT) is a condition in which blood clots form in a vein deep within the body. The word thrombosis means forming a blood clot. The clot itself is called a thrombus.

A blood clot is a jelly-like mass of congealed blood. Clotting is the normal way the body stops bleeding and begins healing following injury. Once the clot has done its job, the body absorbs it. Sometimes, however, blood clotting can prove harmful.

DVT occurs when a blood clot forms in a deep vein and remains there.

DVT usually involves the formation of a large clot in the deep veins in the lower legs and thighs. In rare instances, DVT can occur in the area around the armpit and collar bone (axillary-subclavian vein thrombosis), in the upper arm, abdomen, or pelvic region.

It is a dangerous condition because the clot may become dislodged from the vein and travel inside the vein all the way to the lung, where it may get trapped and block a vessel in the lung. This is called pulmonary embolism, which can be deadly.

Deep vein thrombosis most often occurs in:

	Hospitalized patients following surgery.
	Individuals confined to bed for prolonged periods.
	Healthy individuals whose legs remain immobilized for long stretches of time, such as passengers on lengthy airline flights.

Causes & Risk Factors

	Immobility
	Previous Deep vein thrombosis
	Major Surgery
	Pregnancy
	Oestrogen therapy
	Oral contraceptives
	Extended air travel
	Malignancy
	Blood disorders
	Heart disease
	Injury to leg
	Paralysis

Signs & Symptoms

	Calf pain + Swelling + Redness
	Homan’s sign
	Ankle oedema
	Varicose veins
	Venous gangrene

Differential Diagnosis

	Muscle strain or tear
	Ruptured Baker’s cyst
	Calf muscle abscess
	Haematoma
	Lymphangitis
	Lymphatic obstruction
	Cellulitis

Diagnostic Test

	B-mode USG
	Venous duplex scan
	Plethysmography
	D-dimer
	MRI Venography
	Venography

Thrombophilia screen test

	Thrombin-antithrombin III
	Fibrinopeptide A
	Fibrin monomer
	Protein C
	Fibrin & fibrinogen degradation products
	Tissue plasminogen
	Platelet factor 4
	Beta-thromboglobulin
	Circulating platelet aggregates
	Plasminogen activator inhibitor activity
	Protein S
	Lupus Anticoagulant
	Factor V Ladien

Complications

	Pulmonary embolism
	Post thrombotic leg syndrome

Treatment of Deep Vein Thrombosis

	Anticoagulation
	Thrombolysis
	Thrombectomy
	IVC filter
	Venoplasty
	Stenting

Outcome

	Complete spontaneous lysis of large venous thrombi is uncommon, even in patients treated with heparin. Only 10 % lyse completely.
	Complete lysis however occurs in asymptomatic calf vein thrombi.

Duration of anticoagulation in DVT

	Transient cause and no other risk factor: 3 months
	Idiopathic: 3-6 months
	Ongoing risk; eg. Malignancy: 6-12 months
	Recurrent PE/DVT: 6-12 months
	Pts. With high risk of recurrent thrombosis exceeding risk of anticoagulation: indefinite

Ilio-femoral Venous Thrombosis

	Primary focus – Preventing Pulmonary embolism.
	Secondary focus – Preventing post thrombotic leg syndrome

Intervention

	Thrombectomy
	Thrombolysis
	Purpose – Early and complete removal of thrombus to preserve valve function and remove obstruction.
	PTLS occurs due to obstruction & reflux leading to venous hypertension

Before Thrombolysis	After Thrombolysis
Thrombolysis	Thrombolysis
Thrombolysis	Thrombolysis
Venoplasty	Venoplasty

Thrombolytic therapy

Pharmacologic dissolution of thrombus from the deep venous system appears to be an ideal goal of treatment which has the potential of eliminating deep venous obstruction and maintaining valvular function.

Catheter directed thrombolysis

	In acute DVT < 10 days.
	Urokinase 150,000 U/hr via multi-sidehole catheter.
	Heparin 500 U/hr. concomitantly via popliteal sheath
	Venograms every 12 hrs to reposition infusion devices

Thrombolytic vs Heparin Therapy
Thirteen studies are reported in the literature which compared anticoagulation therapy to thrombolytic therapy for acute deep venous thrombosis. Of the patients treated with thrombolytic therapy, 45% had significant or complete clearing on post-therapy phlebography compared to only 4% of those treated with heparin.

Venous Thrombectomy

	Many vascular surgeons are reluctant to apply these techniques in clinical practice.
	Pooled data from contemporary reports of iliofemoral venous thrombectomy indicate that the early and long-term patency of the iliofemoral venous segment is approximately 80%, contrasted to only 30% of patients treated with anticoagulation alone.

Success

	Thrombectomy - 75%
	Thrombolysis - 80%

Indications for IVC filter

	PE with contraindication to anticoagulation
	Recurrent PE despite adequate anticoagulation
	DVT with free floating Thrombus
	Prophylaxis for orthopaedic trauma

Pregnancy and DVT

	Normal pregnancy is a hypercoagulable state.
	LMWH does not cross placenta and is not secreted in breast milk.
	LMWH should be continued throughout pregnancy and stopped before delivery.
	Anticoagulation- restarted in puerperium and continued for 6 weeks to 3 months

Recurrence

	DVT recurs in 5-10% of pts. The year after ACT is discontinued and 30 % after 8 years.
	Post thrombotic leg syndrome occurs in 50% of pts. with symptomatic DVT. With improved treatment it has decreased to 30 % after 8 years of follow-up.

FAQ

Q. Who is at risk for deep vein thrombosis?

A. Some people are more likely than others to develop thrombosis. Those at risk include:

	The elderly
	Diabetics
	People with blood disorders
	Women who take oral contraceptives (birth control pills) or other medications that contain the hormone estrogen
	People with a history of thrombosis
	People who have just undergone major surgeries or have just suffered a bone fracture.

Facts about deep vein thrombosis:

	Deep vein thrombosis is the second most common vascular problem in the World. The first is varicose veins.
	In India, deep vein thrombosis affects as many as 600,000 individuals every year.
	The condition is most commonly seen in people over age 60, but anyone can be affected.

Unfractionated Heparin

Unfractionated heparin (UFH) has been used for over 50 years in the prevention and treatment of thrombosis. For the treatment of deep-vein thrombosis (DVT) and pulmonary embolism (PE), it is administered by intravenous infusion (i.e. it is infused over a period of time into your vein) and has a rapid anticoagulant effect. You have to be in hospital to receive this treatment. Low-dose UFH is commonly used for prevention of thrombosis (thromboprophylaxis) in patients who are undergoing general surgery, but it is less effective than other forms of prevention in high-risk patients who are undergoing major orthopedic surgery (e.g. hip or knee replacement surgery).

	Side effects
	UFH is associated with a risk of bleeding, heparin-induced thrombocytopenia (low platelet count in the blood) and local reactions in the skin around the site of infusion. Long-term use of UFH may also be associated with an increased risk of osteoporosis (loss of bone tissue leading to brittle bones). If you experience any side effects, you must consult your physician.
	Potential drug interactions
	Before you start taking UFH, you may be asked to stop taking any other treatments that may increase your risk of bleeding (e.g. other anticoagulant and platelet inhibitors, such as aspirin or nonsteroidal anti-inflammatory drugs). If your physician considers it is necessary for you to continue taking these treatments while you are taking UFH, he/she is likely to ensure that you are monitored very carefully.
	Monitoring of therapy
	If you are receiving treatment with UFH, the dose you receive has to be regularly monitored and adjusted to ensure that you are sufficiently protected from thrombosis forming in your veins. Your physician will conduct a blood test (the activated partial thromboplastin time, or aPTT, test) 6 hours after the first dose and at least once a day thereafter to ensure that you are receiving the correct dose of UFH.

Low-molecular-weight heparin

Low-molecular-weight heparin (LMWH) is derived from unfractionated heparin (UFH). It is injected under the skin (i.e. subcutaneous injection) and has a rapid anticoagulant (anticlotting) effect. LMWH has several advantages over UFH, including a predictable response to the dose of drug and a longer-lasting effect. This means that it can be administered only once or twice a day. It is also more convenient to inject under the skin than into a vein, which means that you may be able to inject yourself at home rather than having to go to hospital. LMWH is a highly effective and generally safe form of prevention (thromboprophylaxis) and treatment.

	Side effects
	LMWH is associated with a small risk of bleeding (most commonly minor bleeding), thrombocytopenia (a low platelet count in the blood) and osteoporosis (loss of bone tissue leading to brittle bones). These side effects with LMWH are rare, with bleeding being the most common, but if you experience any side effects, you must consult your physician.
	Potential drug interactions
	Before you start taking LMWH, you may be asked to stop taking any other treatments that could increase your risk of bleeding (e.g. other anticoagulant and platelet inhibitors). If your physician considers it is necessary for you to continue undergoing these treatments while you are taking LMWH, he/she is likely to ensure that you are monitored very carefully.
	Monitoring of therapy
	LMWH is injected at a fixed dose decided in accordance with your weight. There is no need for your physician to monitor or adjust the amount of drug injected once the correct dose has been found (using a blood-clotting test), unless you are pregnant, have kidney failure, weigh more than 100 kg, or are a child.

Oral anticoagulants

The oral anticoagulant warfarin has been used successfully for over 50 years in the prevention of thrombosis.

Warfarin is not recommended for the prevention of thrombosis in patients who are undergoing general surgery. Warfarin, dose-adjusted according to the results of a blood clotting test, is generally safe and effective in the prevention of thrombosis in patients who are undergoing major orthopedic operations (e.g. hip or knee replacement surgery).

Treatment of thrombosis using warfarin is usually started while you are in hospital and can be continued after you are discharged. Warfarin is generally safe; however, it is not effective until at least 3 days after you have taken it and it is only effective within a narrow range of doses (called a therapeutic window). For this reason, when you are first diagnosed with a deep-vein thrombosis (DVT) or pulmonary embolism (PE), you will be given either unfractionated heparin or low-molecular weight heparin together with warfarin for the first few days (up to 1 week) until your blood test shows that the warfarin dosage is effective.

	Side effects
	warfarin is associated with a risk of bleeding complications. It may also cause rash, nausea and diarrhea. If you experience any side effects, you must consult your physician. Warfarin should be avoided during pregnancy.
	Potential drug interactions
	Drug interactions with warfarin can increase the anticogaulant effect which can result in bleeding, or decrease the anticoagulant effect which can lead to an increased risk of DVT. The following are some of the most important drugs with which warfarin interacts: nonsteroidal anti-inflammatory drugs oral hypoglycemics (diabetes drugs) sulfonamides antibiotics drugs affecting liver enzymes (e.g. some cholesterol-lowering drugs, such as carbamazepine) corticosteroids imidazole antifungals (e.g. Amfotericin B, Fluconazole) vitamin K in food (foods that contain high levels of vitamin K include spinach, avocado and cabbage), and dietary supplements (vitamin K helps produce some important blood-clotting factors and decreases the effects of warfarin). Hormonal contraceptives in general You should inform your physician if you are taking any of these drugs or dietary supplements and you are prescribed warfarin. You should also consult your physician for more complete advice on the drugs likely to interact with warfarin, and whether it is necessary to adjust your diet in order to avoid foods high in vitamin K.
	Monitoring of therapy
	If you are prescribed warfarin, you will usually be monitored frequently and closely to minimize the risk of serious bleeding complications. Your physician may also periodically conduct a blood test (PT/INR) to ensure that you are receiving the correct dose of warfarin. The standardized method for reporting the results of this test is called the international normalized ratio (INR). The aim of your treatment will be to keep your INR within a certain range.

Other treatment options

Other treatment options for deep-vein thrombosis or pulmonary embolism (PE) include thrombolytic therapy, thrombectomy and inferior vena cava interruption.

Thrombolytic medications

Thrombolytic medications break down the blood clot, i.e. they cause the clot to disintegrate. They are usually used in combination with anticoagulant. These agents are very expensive and are associated with a high incidence of bleeding. They are not necessary for most patients with pulmonary embolism, but can be life-saving in patients with a very large pulmonary embolism that obstructs the flow of blood to the lungs.

Thrombectomy

Thrombectomy is the surgical removal of a thrombosis. This technique is of limited use for blood clots in veins and is 50% successful in preventing a further thrombosis.

Inferior vena cava interruption

Partial interruption of the inferior vena cava (the vein that carries blood from the lower body to the right side of the heart) using clips, sutures (stitches) or filters prevents the blood clot from reaching the lung. This technique is usually considered in situations where anticoagulant medication cannot be used because of bleeding, or in situations of repeated thrombosis despite the use of antithrombotic medication.