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See Also

Peripheral Artery Disease: causes and consequences

Coronary Artery Disease: causes and consequences

Introduction to Venous Thromboembolism

This section introduces venous thromboembolic disorders, their incidence, prevalence, classification and risk factors

Formation of a blood clot – a thrombus – within a vein is known as venous thrombosis. Venous thrombosis can occur in any vein, but the most common manifestation is DVT, which occurs predominantly in the large veins in the leg.1,2 A DVT may form without a known reason, but the risk is higher (for example):

  • If a leg has been immobilized for a long period, such as after a surgical operation or even after long-distance air travel
  • If a patient has a medical condition such as cancer
  • During pregnancy

Deep vein thrombosis

If part or all of a DVT or other thrombus breaks away from the blood vessel wall and travels through the venous blood system, it is known as an embolus.2

  • An embolus that is carried in the direction of blood flow towards the lungs can block one of the arteries in the lung. This is known as a PE
  • Patients with DVT are at risk of PE, which can potentially be life-threatening

Pulmonary embolism

Collectively, DVT and PE are known as VTE.

VTE is a major healthcare problem worldwide

  • In 2007, over 500,000 deaths in the EU were associated with an estimated 1.1 million venous thromboembolic events – approximately one-third of these events manifested as PE3
  • In the US, DVT and PE together affect an estimated 350,000–600,000 people each year, leading to an estimated 100,000–300,000 deaths4,5
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VTE is a major cause of death. European data for 20073
AIDS, acquired immunodeficiency syndrome

Although the annual incidence of VTE is estimated at approximately 1 in 1000 of the population,6,7 certain groups are at considerably higher risk. For example, routine screening of patients in clinical trials showed the DVT frequency without prophylaxis to be:

  • 15–40% in medical or general surgical patients and 40–60% in those who had major orthopaedic surgery8
  • Up to 41% of patients worldwide, those hospitalized for an acute medical illness are at risk of developing VTE9

Approximately half of diagnosed venous thromboembolic events are classed as provoked (caused by a known risk factor or factors), the other half are unprovoked (idiopathic), meaning that the cause is not known7,8,10

  • Known risk factors for VTE are either reversible (temporary) or not (intrinsic)
  • A patient may initially be diagnosed with unprovoked VTE, but this may be because the provoking risk factor, often cancer, has not yet been identified
  • Multiple risk factors generally have a cumulative impact on the risk of VTE

Classification of VTE7,8,10

Among the reversible risk factors, surgery – especially major orthopaedic surgery involving the lower limbs and major surgery for cancer – acute medical illness, often involving immobilization, and pregnancy are major risk factors for VTE.


Next section: Prevention of VTE


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