Bayer Pharma AG

Essence of this Article

Formation of a thrombus within a vein is known as a venous thrombosis. If the thrombus breaks loose and travels through the circulatory system, it is known as an embolus. Venous thrombi manifest mainly as deep vein thrombosis (DVT) and pulmonary embolism (PE). DVT is the most common type of venous thromboembolism (VTE), but patients with DVT are also at risk of PE, which can potentially be life-threatening. VTE is associated with cancer, trauma and surgery, and several pre-disposing risk factors, including pregnancy, obesity and immobility, have been identified. VTE can also lead to serious long-term complications, including post-thrombotic syndrome (PTS) and chronic thromboembolic pulmonary hypertension (CTEPH).

Venous Thrombosis

Venous Thrombosis - Deep Vein Thrombosis Risk Factors

Deep vein thrombosis

Venous Thrombi

Formation of a thrombus within a vein is known as a venous thrombosis. If the thrombus breaks loose and travels through the blood system, it is known as an embolus.36

Venous thrombi:

  • Feature enmeshed erythrocytes
  • Tend to fragment, creating an embolus
  • Manifest mainly as DVT and PE
Pulmonary embolus

Pulmonary embolus

Venous thromboembolism

The most common type of VTE is DVT, which occurs predominantly in the large veins in the leg.25, 36

When part or all of a thrombus breaks away from the blood vessel wall, this thrombus is carried in the direction of blood flow towards the lungs and can block one of the arteries in the lung (pulmonary embolus). Patients with DVT are at risk of PE which can potentially be life-threatening.

Risk factors

VTE is associated with cancer, trauma and surgery. Idiopathic cases occur where a patient has no clear exposing risk factor (i.e. no triggering event).37 Important risk factors for VTE include:38

Pre-disposing risk factors:

  • Increasing age (especially >60 years)
  • Pregnancy and postpartum
  • Obesity (body mass index >30 kg/m2)
  • Immobility (including lower extremity paralysis)
  • Personal/family history of VTE
  • Dehydration
  • Use of oestrogen-containing oral contraceptives
  • Use of hormone replacement therapy

Exposing risk factors:

  • Surgery
  • Active cancer or cancer therapy
  • Respiratory or heart failure
  • Acute medical illness
  • Critical care admission
  • Venous compression (e.g. by tumour, haematoma, arterial abnormality)
  • Recent myocardial infarction or stroke
  • Metabolic, endocrine or respiratory pathologies
  • Central venous catheterization
  • Inflammatory bowel disease (e.g. ulcerative colitis or Crohn’s disease)
  • Severe infection
  • Myeloproliferative diseases
  • Varicose veins with associated phlebitis
  • Inherited or acquired thrombophilias
  • Selective oestrogen receptor modulators
  • Erythropoiesis-stimulating agents
  • Nephrotic syndrome
  • Paroxysmal nocturnal haemoglobinuria
  • Long distance travel

Incidence and prevalence

Venous thromboembolic disease is a major problem worldwide, causing more than half a million deaths every year in the European Union (EU).39

In 2007, it was estimated that approximately 1.1 million venous thromboembolic events occur each year across the EU encompassing:39

  • 1,118,742 total venous thromboembolic events

    • 684,019 (61% of total) DVT events
    • 434,723 (39% of total) PE events
  • 543,454 (49% of total) VTE-related deaths

In the United States (US), the Surgeon General has stated that DVT and PE together affect an estimated 350,000–600,000 people each year,40 leading to an estimated 100,000–300,000 deaths annually.40, 41

The annual incidence rate of VTE (adjusted for age and sex) has been reported to be 1.17 per 1000 per year over a 25-year period in a US population-based study, or:42

  • DVT – 0.48 per 1000 population per year
  • PE – 0.69 per 1000 population per year

In the EU, it is estimated that more than 1.1 million cases of VTE occur each year, leading to over half a million deaths.1 It has also been noted that VTE is responsible for more than twice the number of deaths than those caused by AIDS, breast cancer, prostate cancer and road traffic accidents combined.39


VTE also can lead to serious long-term complications, including:

  • PTS
  • CTPH30

PTS is the most common complication of DVT and typically causes chronic pain and swelling in the affected leg, and in severe cases can result in venous ulcers.44

After symptomatic DVT, 20–50% of patients develop PTS.44

CTEPH is a serious long-term complication of PE, but it can be difficult to diagnose because clinical symptoms and signs are non-specific or absent in early CTEPH. Many of the symptoms are similar to those for acute PE, including dyspnoea, chest pain, pre-syncope or syncope and/or haemoptysis.39, 45 CTEPH causes the right side of the heart to work harder than normal owing to abnormally high blood pressure in the arteries of the lungs. This can lead to heart failure and other serious consequences.

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