Venous thromboembolism
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.

# Overiew
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.

# Classification
Venous thromboembolism (VTE) may be classified into:
- Deep vein thrombosis (DVT)
- Pulmonary embolism (PE)
The following table further classifies DVT and PE:

# Epidemiology

## Prevalence
- 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.

## Incidence
- 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.
- 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.
- In the United States, the annual incidence of VTE is estimated to be approximately 100 per 100,000 persons.

## Age
- 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.
- 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.

## Gender
- Studies about differences in the incidence of VTE by gender have yielded mixed results:
Some reported a higher incidence of DVT among young females.
Some reported a higher incidence of DVT among older females.
Some reported a higher incidence of DVT in men.
- Some reported a higher incidence of DVT among young females.
- Some reported a higher incidence of DVT among older females.
- Some reported a higher incidence of DVT in men.
- In addition, the risk for DVT was reported to consistently increase with age across both genders.

## Race
- There is a significant difference in the incidence of DVT as it relates to race. African Americans characteristically have the highest incidence of DVT while Caucasians rank as the second highest incidence of DVT.
- Compared to African Americans and Caucasians, the incidence of DVT is noted to be two to four times lower in Hispanics and Asian-Pacific Islanders.
- Lower incidence of thrombosis in non-Caucasians may be related to a lower prevalence of disorders like Factor V Leiden or Prothrombin 20210A mutation.

## Hospitalization for VTE
- During 20072009, 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.
- The estimated average annual number of hospitalizations with VTE was successively greater among older age groups: 54,034 for persons aged 1839 years; 143,354 for persons aged 4059 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).
- 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.
- 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 1839 years, 143 for persons aged 4049 years, 200 for persons aged 5059 years, 391 for persons aged 6069 years, 727 for persons aged 7079 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.
- 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.

## Recurrence of VTE
- Approximately 33% (1 in 3) of people with VTE will have a recurrence within 10 years.
- 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.
- 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.
- The recent increase in thrombosis incidence may be related to improved diagnostic modalities and increased awareness by clinicians.

## 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.
- Among people who have had a DVT, one-half will have long-term complications (post-thrombotic syndrome) such as swelling, pain, discoloration, and scaling in the affected limb.

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

# Diagnosis
The diagnostic guidelines for venous thromboembolism are as follows:

## Deep Vein Thrombosis

## Pulmonary Embolism
Pulmonary embolism Wells Score Calculator

# Prevention
The following table summarizes major scoring criteria for risk assessment of VTE:
The following table summarizes the major scoring criteria used for risk assessment of VTE and their prophylaxis options:
Abbreviations: LDUH: low dose unfractionated heparin; LMWH: low molecular weight heparin; VTE: Venous thromboembolism