What is Deep Vein Thrombosis (DVT)?

Deep Vein Thrombosis (DVT) is formation of a blood clot-Thrombus in the deep veins of legs and in rare cases the arms. It forms spontaneously and cause blood to stop flowing in the affected vein.

The biggest danger about it is not the blockade of the blood vessel but it’s when the clot dislodges from the vessel and travel to block blood vessels in important structures like the Heart and lungs. It results in death if left untreated due to the mentioned complication.

How Blood Clots?

Under normal circumstances the blood flows smoothly inside the blood vessels with no problem. When you get injured and bleed, the blood vessels detect an injury in their lining and release clotting factors which initiate formation of blood clot to stop the bleeding.

Steps involved in blood clotting.
How blood clots

Blood clotting is also triggered by turbulent flow in the blood and reduced blood flow speed which happens in the veins if you are bedridden for a long time. When the blood vessel has healed, the body release chemicals which cause Thrombolysis-the destruction of blood clot.

When the blood clot is small enough it dislodges from the original site and enter the blood stream where it completely dissolves in a few moments.

What Happens in Deep Vein Thrombosis?

Deep vein Thrombosis: a clot in the leg.
a clot in the leg

The Blood clots spontaneously in the deep veins of the leg due to the causes to be mentioned shortly, as the clot grows bigger, it obstructs the vein initially causing more turbulent flow. Remember turbulent flow triggers formation of clots. The clot becomes big enough to block the vein and start to cause symptoms.

If left untreated, the clot dislodges to the lungs and cause death in more than 50% of those affected, in a complication called Pulmonary Embolism. Pulmonary Embolism is a medical emergency that require urgent treatment to dissolve the blood clot that’s blocking the pulmonary vessels.

Causes and Risk Factors of DVT

There are many causes and risk factors of Deep Vein Thrombosis which can be grouped in Two ways:

1.Factors that cause Decreased blood flow speed:

  • Being admitted in hospital for more than a week- especially if you cannot walk on your own and always bedridden
  • Stroke: If the lower limbs are affected
  • Paraparesis: Paralysis of the lower body
  • Having a Fractured leg: It happens when the cast put on the leg causes decreased mobility
  • Long distance travels either by air or land transport, as long as you’re immobile for extended period of time.

2.Factors that cause increased clotting risk (Hypercoagulable state)

These are factors that increase the risk of spontaneous formation of a Thrombus (blood clot) without any injury or trauma. Read this list carefully and take note

  • Pregnancy
  • Oral contraceptives (The Pill)
  • Blood Disorders like Thrombophilia and Polycythaemia
  • Cancer
  • HIV
  • Obesity
  • Autoimmune Diseases like SLE
  • Alcohol and smoking

3.Other Factors

  • Major abdominal surgery like caesarean section or leg surgery
  • Advanced age
  • Cancer treatment
  • Previous History of DVT

Symptoms of Deep Vein Thrombosis

DVT starts as a swelling of one leg developing over a week to a few weeks.

The swelling is accompanied by pain of the calf muscle on the affected leg and feeling like the leg is heavy. As time goes on the pain becomes more severe and the calf muscles become hard due to the accumulation of blood in the deep vein that is blocked.

Pulmonary Embolism (PE), which happens when the DVT is left untreated for a long time is characterized by sudden severe chest pain and shortness of breath. The shortness of breath is severe even at rest. It is accompanied by Sweating, Dizziness and coughing blood sometimes.

PE is a deadly medical emergency that requires prompt treatment. Those who survive the initial stages of Pulmonary Embolism usually suffer from Heart Failure shortly after the attack.

Diagnosis of DVT

DVT diagnosis Requires careful history and Physical examination by the physician. Blood tests and Scans are done to confirm a suspected DVT based on the Wells Score.

Wells Score

Clinical FeaturesScore
Active cancer (treatment within last 6 months or palliative)1
Paralysis, Paresis or Recent Leg immobilisation with cast1
Recently Bedridden for >3 days or Major surgery in last 3 months1
Local Tenderness along distribution of deep veins1
Entire Leg swollen1
Pitting Oedema1
Collateral superficial veins (non-Varicose)1
Calf swelling >3cm compared with asymptomatic leg1
Alternative diagnosis at least as likely as DVT-2
Previously documented DVT1
Wells Score

A score of 2 or more suggests DVT.

Blood Tests: The most sensitive test of all is D-dimer test, which is usually elevated in DVT. Other tests are done as well to assess an increase in risk of clot formation such as Platelet count, Full Blood Count, Clotting Factors, INR, PT and aPTT.

Scans: Duplex Doppler Ultrasound scan is used to detect the location and size of the thrombus in the vein.

Treatment of DVT

Once the diagnosis is made, treatment is started immediately. The main treatment of Deep Venous Thrombosis is to give Anticoagulants such as Warfarin and Heparin. The patient is usually admitted in hospital to closely watch for any signs of Pulmonary Embolism.

 Duration of Anticoagulants is individualized with some patients receiving it for 3-6 months while it is lifelong for others. If Anticoagulants fail or the patient has active bleeding, Inferior Vena Caval (IVC) Filters are used. The risk with use of IVC filter is Recurrent DVT and increased risk of Bilateral swelling when it is blocked

Patients that are categorized as being at risk of having a clot are given treatment to prevent DVT.

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