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Deep Vein Thrombosis

Introduction

The venous system is a complex network covering the entire body. It consists of superficial veins, deep veins and perforating veins connecting the deep and superficial networks.

A Deep Vein Thrombosis (DVT) refers to a blood clot in the deep venous system. Although DVT’s can occur anywhere in the deep veins, they are most common in the deep veins of the thighs and calves. The legs are more prone to the effects of gravity, which can cause pooling and stasis of blood. This in part explains why most DVT’s are found in the lower limbs.

Causes

There are three factors (Virchow’s triad) leading to thrombosis, generally the formation of thrombus requires two of these three factors. These are blood stasis, alteration to the vein wall, and hypercoagulability (sticky blood).

You are at more risk of developing a DVT if you have the following:

  • Metabolic syndrome.
  • Previous history of DVT.
  • Personal or family history of a clotting disorder.
  • Recent major surgery or injury.
  • Hospitalisation.
  • History of active cancer and concurrent cancer therapy.
  • Smoking.
  • Obesity or being overweight.
  • Hormone replacement therapy or high dose combined oral contraceptive pill.
  • Pregnancy and first six weeks after delivery.
  • Prolonged sitting, that is greater than 6-8 hours.

Sign and Symptoms

The main symptoms of DVT are pain and swelling. The local area may feel warmer.

DVT’s can cause skin inflammation and ulceration. The effects depend on where the blood clot is and whether or not the clot has completely blocked the deep vein.

Pulmonary embolus occurs if a blood clot breaks off and travels to the lungs. Depending on its size and where it lodges, this embolus can be life threatening or cause death. If you have a ‘hole in the heart’ the clot can embolise to the brain (stroke), upper limb or arterial circulation in the abdomen or legs.

In some instances, a DVT causes ongoing chronic problems in the leg. This is called Post Thrombotic Syndrome (PTS). Residual clot in the vein can obstruct venous return and cause the limb to swell. The clot may permanently damage the one way valves in the deep veins, allowing blood to fall down the leg towards the ankles instead of circulating up the leg and to the heart. This adds to the swelling and venous hypertension.

Diagnosis

  • Physical examination.
  • Ultrasound.

Symptoms of a DVT can mimic other conditions, it is best diagnosed by ultrasound.

Treatment

Treatment and management may include clot dissolving drugs, surgical or endovascular thrombectomy, blood thinning medication, compression stockings, avoidance of the risk factors where possible, and blood tests to identify possible clotting disorders.

Wearing compression as instructed by your doctor can reduce the likelihood of PTS. This means wearing compression as soon as a DVT is diagnosed and wearing compression for an extended period of time, possibly years or forever.

Compression stockings are very firm on the leg and help the leg muscles push blood out of the leg and to the heart. This decompresses the pressure in the leg. This also helps to clear clot in the acute setting.