venous thromboembolism

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Venous thromboembolism (VTE) is when a thrombus (blood clot) forms in a vein which may dislodge from its site of origin to travel in the blood, an occurrence known as embolism (1).

  • majority of thrombus formation occurs in the deep veins of the leg, hence the most frequent manifestation of VTE is deep venous thrombosis (DVT)
    • almost two thirds of VTE cases are isolated DVTs (2)
  • a dislodged thrombus may travel to the lung and cause pulmonary embolism (PE) (1,3).

It is the third most commonest vascular disease after coronary artery disease and stroke (4).
Incidence of VTE increases sharply with age:

  • women are more often affected at a younger age while in the elderly, this ratio reverses
  • a lower incidence is seen in Asians (2)

VTE is an important cause of death in hospitalised patients (1).

  • all patients admitted to the hospital or presenting acutely to hospital should be individually assessed for risk of VTE and bleeding
  • this assessment should be repeated regularly and at least every 48 hours (5)

Venous thromboembolism (VTE), clinically presenting as DVT or PE, is globally the third most frequent acute cardiovascular syndrome behind myocardial infarction and stroke (6):

  • annual incidence rates for PE range from 39-115 per 100 000 population; for DVT, incidence rates range from 53-162 per 100 000 population
  • cross-sectional data show that the incidence of VTE is almost eight times higher in individuals aged >= 80 years than in the fifth decade of life.

Various risk factors for VTE have been categorised (6)

Strong risk factors (Odds Ratio (OR) > 10)

Fracture of lower limb
Hospitalization for heart failure or atrial fibrillation/flutter
(within previous 3 months)
Hip or knee replacement
Major trauma
Myocardial infarction (within previous 3 months)
Previous VTE
Spinal cord injury








Moderate risk factors (OR 2- 9)

Arthroscopic knee surgery
Autoimmune diseases
Blood transfusion
Central venous lines
Intravenous catheters and leads
Congestive heart failure or respiratory failure
Erythropoiesis-stimulating agents
Hormone replacement therapy (depends on formulation)
In vitro fertilization
Oral contraceptive therapy
Post-partum period
Infection (specifically pneumonia, urinary tract infection, and HIV)
Inflammatory bowel disease
Cancer (highest risk in metastatic disease)
Paralytic stroke
Superficial vein thrombosis


Weak risk factors (OR < 2)

Bed rest >3 days
Diabetes mellitus
Arterial hypertension
Immobility due to sitting (e.g. prolonged car or air travel)
Increasing age
Laparoscopic surgery (e.g. cholecystectomy)
Varicose veins








HIV = human immunodeficiency virus; OR = odds ratio


Last edited 05/2020 and last reviewed 07/2021