Venous thromboembolism

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Venous thromboembolism Microchapters

Patient Information

Deep vein thrombosis
Pulmonary embolism




Risk Factors



Deep Vein Thrombosis
Pulmonary Embolism


Editor-In-Chief: C. Michael Gibson, M.S., M.D. [2]; Associate Editor(s)-in-Chief: Syed Hassan A. Kazmi BSc, MD [3], Iqra Qamar M.D.[4], Anmol Pitliya, M.B.B.S. M.D.[5], Aravind Reddy Kothagadi M.B.B.S[6]

To review the risk of VTE according to IMPROVEDD score, click here.

To review the risk of VTE according to IMPROVE score, click here.

To review the risk of VTE according to Caprini scores click here.

To predict the clinical risk of Pulmonary thromboembolism according to Wells score, click here.


Venous thromboembolism (VTE) may be classified into deep vein thrombosis (DVT) and pulmonary embolism (PE). Pulmonary embolism may arise as a consequence of deep vein thrombosis as a result of embolization of the clot from deep veins of the legs. Pulmonary embolism (PE) is an acute obstruction of the pulmonary artery (or one of its branches). The obstruction in the pulmonary artery that causes a PE can be due to thrombus, air, tumor, or fat. Most often, pulmonary embolism is due to a venous thrombosis (blood clot from a vein), which has been dislodged from its site of formation in the lower extremities. It has then embolized to the arterial blood supply of one of the lungs. Deep vein thrombosis (also known as deep venous thrombosis or DVT and colloquially referred to as "economy class syndrome") is the formation of a blood clot ("thrombus") in a deep vein.


Venous thromboembolism (VTE) may be classified into:[1][2]

The following table further classifies DVT and PE:[3][4][5][6][5][7][8][9]

Classification of Venous Thromboembolism
Clinical diagnosis Sub-classification Comments
Deep vein thrombosis Upper extremity
Lower extremity
Pulmonary embolism (PE) Massive PE (High risk)



Sub-massive PE (Intermediate risk PE)


Low risk PE



  • The precise number of people affected by DVT/PE is unknown,although as many as 900,000 people could be affected (100 to 200 per 100,000) each year in the United States.[10]


  • The incidence of VTE increases with age, ranging from less than 5 cases per 100,000 people in childhood to 500 cases per 100,000 people in the elderly.[11]
  • Those who are more than 65 years of age are at three times higher risk for VTE compared to those who are 45-54 years old.[12]
  • In the United States, the annual incidence of VTE is estimated to be approximately 100 per 100,000 persons.[11]


  • The incidence of VTE increases with age, ranging from less than 5 cases per 100,000 people in childhood to 500 cases per 100,000 people in the elderly.[11]
  • Those who are more than 65 years of age are at three times higher risk for VTE compared to those who are 45-54 years old.[12]


  • Studies about differences in the incidence of VTE by gender have yielded mixed results:
  • In addition, the risk for DVT was reported to consistently increase with age across both genders.[12]


Hospitalization for VTE

  • During 2007–2009, an estimated annual average of 547,596 hospitalizations culminated in a diagnosis of VTE for adults aged ≥18 years. Estimates for DVT and PE diagnoses were not mutually exclusive. An estimated annual average of 348,558 adult hospitalizations resulted in a diagnosis of DVT, and 277,549 adult hospitalizations resulted in a diagnosis of PE. An estimated annual average of 78,511 adult hospitalizations (14% of overall VTE hospitalizations) had diagnoses of both DVT and PE.[18]
  • The estimated average annual number of hospitalizations with VTE was successively greater among older age groups: 54,034 for persons aged 18–39 years; 143,354 for persons aged 40–59 years; and 350,208 for persons aged ≥60 years. The estimated average annual number of hospitalizations with VTE was comparable for men (250,973) and women (296,623).[18]
  • Shown below is an image depicting the estimated average annual number of hospitalization with a diagnosis of DVT, PE, or VTE by age and sex.
Estimated average annual number of hospitalizations with a diagnosis of deep thrombosis (DVT), pulmonary embolism (PE), or venous thromboembolism (VTE), by patient sex and age group — National Hospital Discharge Survey, United States, 2007–2009 - Source:CDC
  • The average annual rates of hospitalizations with a discharge diagnosis of DVT, PE, or VTE among adults were 152, 121, and 239 per 100,000 population, respectively. For VTE, the average annual rates were 60 per 100,000 population aged 18–39 years, 143 for persons aged 40–49 years, 200 for persons aged 50–59 years, 391 for persons aged 60–69 years, 727 for persons aged 70–79 years, and 1,134 for persons aged ≥80 years. The rates of hospitalization were similar for men and women, and the point estimates increased for both sexes by age.[18]
  • On average, 28,726 hospitalized adults with a VTE diagnosis died each year. Of these patients, an average of 13,164 had a DVT diagnosis and 19,297 had a PE diagnosis; 3,735 had both DVT and PE diagnoses.[18]

Recurrence of VTE

  • Approximately 33% (1 in 3) of people with VTE will have a recurrence within 10 years.[19][20]
  • The risk of recurrence of VTE in patients diagnosed with first-time VTE is estimated to be approximately 7-8% per year during an average follow up period of 2.2 years of subsequent observation.[12]
  • Among patients with a first episode of VTE, the risk of recurrence of VTE is particularly elevated in the first 6 to 12 months following the first episode of VTE. The risk of recurrent VTE remains up to 10 years, with a estimated cumulative incidence of first overall VTE recurrence of 30%. Predictors for recurrence of VTE include malignancy, neurological diseases, and paresis.[21]
  • The recent increase in thrombosis incidence may be related to improved diagnostic modalities and increased awareness by clinicians.[11]

Complications of VTE

  • Estimates suggest that 60,000-100,000 Americans die of VTE, 10 to 30% of which will die within one month of diagnosis.[19][20]

Risk Factors

Shown below is a list of predisposing factors for VTE. The risk factors are classified as moderate or weak depending on how strongly they are associated with a VTE.[22][23][24][25]

Moderate risk factors Weak risk factors

Chronic heart failure
Respiratory failure
Hormone replacement therapy
Oral contraceptive pills
❑ Prior history of VTE


❑ Advanced age

Laparoscopic surgery
❑ Prepartum
Varicose veins

Risk factors of VTE may be categorized into modifiable, non-modifiable, temporary, and other risk factors.

Modifiable Risk Factors Non-Modifiable Risk Factors Temporary Risk Factors Other Risk Factors

❑ Modifiable risk factors are reversible based upon lifestyle/behavior modification.
Obesity is defined as a body-mass index (BMI) above 30 kg/m2.[26] [27] [28]
Smoking:[26] Smoking significantly increases the risk of DVT, particularly among women who are taking oral contraceptive pills as well as among obese people.
❑ Use of oral contraceptives[29]
Hyperhomocysteinemia:[30] Hyperhomocysteinemia can be reduced with vitamin B supplementation.

❑ Advanced age
Heart failure
Thrombophilia or hypercoagulable state
Polycythemia vera

Factor V Leiden
Prothrombin G20210A mutation
Protein C deficiency
Protein S deficiency
Activated protein C resistance
Antithrombin III deficiency
Factor VIII mutation
Antiphospholipid syndrome
Heparin induced thrombocytopenia
Nephrotic syndrome
Paroxysmal nocturnal hemoglobinuria

Pregnancy and the peri-partum period
❑ Active cancer
Central venous catheterization

❑ Other possible factors associated with VTE include:[31]

Nutrition low in fish
Psychological stress
❑ Cardiovascular risk factors such as diabetes and hypercholesterolemia


The diagnostic guidelines for venous thromboembolism are as follows:[32][33][34][35]

Deep Vein Thrombosis

Suspected DVT
Clinical probability
Clinical probability
Repeat ultrasound in 1 week

Pulmonary Embolism

Suspected pulmonary embolism
If signs of DVT present
PE unlikely with positive D-dimer or PE likely
PE unlikely with positive D-dimer or PE likely
V/Q scan
Non diagnostic
High probability
PE present
PE absent
PE unlikely
PE likely
Serial ultrasound
CTPA or serial ultrasound

Pulmonary embolism Wells Score Calculator

Variable Wells Score[36]
Clinically suspected DVT (leg swelling, pain with palpation) 3.0
Alternative diagnosis is less likely than PE 3.0
Immobilization/surgery in previous four weeks 1.5
Previous history of DVT or PE 1.5
Tachycardia (heart rate more than 100 bpm) 1.5
Malignancy (treatment for within 6 months, palliative) 1.0
Hemoptysis 1.0


The following table summarizes major scoring criteria for risk assessment of VTE:[37][38][39][40]

Scoring criteria for risk assessment*
Type of patient Scoring system Score Risk
Non-surgical patient IMPROVEDD Score Predicted % VTE risk through 42 days
0 0.4%
1 0.6%
2 0.8%
3 1.2%
4 1.6%
5-10 2.2%
Predicted % VTE risk through 77 days
0 0.5%
1 0.7%
2 1.0%
3 1.4%
4 1.9%
5-10 2.75
IMPROVE score Predicted % VTE risk through 3 months
0 0.5%
1 1.0%
2 1.7%
3 3.1%
4 4%
5-8 11%
Padua Score < 4 Low risk for VTE
≥ 4 High risk for VTE
Surgical patient Caprini score 0-1 Low risk of VTE
2 Moderate of VTE
3-4 High risk of VTE
≥ 5 Highest risk for VTE

The following table summarizes the major scoring criteria used for risk assessment of VTE and their prophylaxis options:[41][42][43][44][45][39][46][38][47][48][49]

Patient population Sub-population Scoring criteria for risk assessment Major predisposing risk factors and their score Prophylaxis recommendations
Padua score IMPROVE score Caprini score
Non-surgical patients Acutely ill patients - IMPROVE:
IMPROVE bleeding risk:
Cancer in outpatient - - -
  •  Does the patient have a solid tumor 


  • Additional risk factors for VTE?
  • Previous VTE
  • Hormonal therapy
  • Immobilization
  • Angiogenesis inhibitors
  • Thalidomide
  • Lenalidomide
  • If major predisposing risk factors present:
  • If no major predisposing risk factors present:
    • No VTE prophylaxis
Long travel - - -
  • Frequent ambulation
  • Calf muscle excercise
  • Sitting in an isle seat
  • Below knee compression stockings (15-30 mm Hg pressure at ankle)
Surgical patients Orthopedic surgery patients - - -
General and abdominal pelvic surgeries - - Caprini:
Cardiac surgery - -
Thoracic surgery - -
Craniotomy - -
Spinal surgery - -
Trauma - -

Abbreviations: LDUH: low dose unfractionated heparin; LMWH: low molecular weight heparin; VTE: Venous thromboembolism


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