Venous thromboembolism (VTE) occurs when a blood clot, or thrombi, forms in a deep vein. VTE describes two separate, but often related conditions: deep vein thrombosis (DVT) and pulmonary embolism (PE).

DVT commonly causes blood clots to develop in the lower legs or thighs. It can also impact veins in the:

  • pelvis
  • arms
  • mesentery (lining of the abdominal cavity)
  • brain

PE occurs when a piece of a deep vein clot breaks off, travels through the bloodstream, and becomes stuck in a blood vessel in the lungs.

VTE affects some 10 million people worldwide, and is the third leading cause of cardiovascular related deaths. In the United States, there are between 100,000 and 300,000 VTE-related deaths each year.

VTE can occur in anyone, regardless of age, gender, ethnicity, or race. Certain factors can increase your risk for developing this condition, including:

  • medical conditions and procedures
  • medications
  • lifestyle habits

Strong risk factors

The leading risk factor for VTE is long-term hospitalization. Approximately 60 percent of all VTE cases develop within 90 days of hospitalization.

The most common types of surgery associated with VTE are orthopedic surgeries, especially knee and hip replacements.

Additional risk factors for VTE include:

  • major surgery
  • injuries that cause vein trauma, like fractures, muscle damage, long-bone breaks, and spinal cord injuries
  • illnesses that lead to extended periods of bed rest and decreased mobility, like pneumonia and cancer
  • obesity (people who are obese are two times more likely to develop VTE than people who are not obese)
  • age (the risk of VTE begins to increase after the age of 40, and doubles with each decade beyond 40)
  • jobs that involve sitting for long periods, like transportation, computer, and desk-based jobs
  • a history of VTE
  • genetic conditions that cause abnormal blood clotting
  • blood vessel trauma
  • neurological conditions that impact mobility, like Parkinson’s disease and multiple sclerosis
  • travel that requires long periods of sitting
  • chronic heart and lung conditions, like congestive heart failure and obstructive pulmonary disease
  • conditions that cause chronic inflammation, like arthritis and irritable bowel syndrome
  • high blood pressure
  • metabolic conditions, like diabetes
  • extended exposure to air pollution

Moderate risk factors

There are several moderate risk factors associated with VTE. Generally, these factors are not strongly linked with VTE when in isolation, but having two or more of the moderate risk factors for VTE can significantly increase the likelihood of developing the condition.

Moderate risk factors for VTE include:

Currently there’s no scientific consensus on whether VTE is more likely to be seen in men or women.

Pregnancy and VTE risk

A few specific factors may increase the risk of VTE during pregnancy and shortly after giving birth. Risk factors for pregnancy and birth-related VTE include:

  • a personal or family history of VTE
  • obesity
  • older maternal age
  • illness or infection during pregnancy
  • bed rest or long-distance travel
  • multiple gestation

A doctor will assess your risk for VTE by gathering information and asking questions about certain factors, including:

  • age
  • weight
  • medical history
  • current medications
  • family history
  • lifestyle habits

A doctor will also ask you questions about any potential symptoms or concerns.

Based on how many risk factors are present, a doctor will determine whether you’re in a low, moderate, or high-risk category for VTE. Generally, the more individual risk factors for VTE you have, the greater your risk of developing the condition.

If your doctor thinks you have VTE, they’ll usually assess your risk with the help of mathematical modeling. The next step is a D-dimer test blood test, which is used to detect clots.

If further testing is needed, then they should use a VQ scan, according to 2018 guidelines from the American Society of Hematology. VQ scans require less radiation than computed tomography (CT) scans.

A doctor or surgery team should always assess your risk of VTE when being admitted to the hospital, especially for surgery or disabling conditions. You can be proactive and bring along a VTE fact sheet containing questions to ask your doctor, and spaces for the doctor’s notes about your prevention and treatment plan.

In some cases, VTE doesn’t cause any noticeable symptoms. Recognizing the warning signs of both DVT and PE is important, as both require immediate medical attention.

Symptoms of DVT include:

  • swelling, especially in the foot, ankle, hands, or wrists
  • pain and soreness, often beginning in the calf, thigh, or forearm
  • warmth in the affected area
  • redness or discoloration of the affected area

Symptoms of PE include:

  • chest pain that may worsen with deep breathing
  • rapid breath and heart rate
  • unexplained difficulty breathing, usually shortness of breath or shallow breathing
  • feeling lightheaded or dizzy
  • loss of consciousness

If you’re in a moderate, or high-risk category for VTE, your doctor will likely recommend a prevention plan involving medication, therapeutic devices, and lifestyle changes.

Common medical preventative measures for VTE include:

  • anticoagulants, which are blood thinning medications
  • compression socks, stockings, wraps, or braces
  • intermittent pneumatic compression devices
  • rapid inflation venous foot pumps

Common lifestyle tips for preventing VTE include:

  • avoid sitting or being inactive for long periods of time
  • increase physical activity or exercise
  • if you’re inactive, do leg, foot, arm, and hand stretches as soon and often as possible, especially during hospitalization, bed rest, or other periods of immobility
  • stop or avoid excessive or long-term alcohol consumption
  • stop smoking
  • wear loose fitting clothes

If DVT is diagnosed, additional preventive measures may be taken to reduce your risk for PE. In some cases, the deep vein clot may need to be surgically removed. A piece of mesh may also be sewn into the body’s largest vein, the inferior vena cava, to act as a filter. The mesh can be used to trap pieces of clots and prevent them from reaching the lungs.

All cases of VTE are life threatening and require immediate medical care.

Blood clots, especially those in the lungs, can block blood flow, leading to hypoxia. Hypoxia is tissue death from oxygen starvation.

Large clots or obstructions can result in organ damage, coma, and eventually death. An estimated 30 percent of people with untreated PE die, often within hours of developing the condition. That’s why it’s important to understand your risk and recognize the signs.

VTE is largely considered to be a preventable condition because most cases develop in the hospital or involve at-risk individuals. When treated early and aggressively, the worst complications associated with VTE can often be avoided.