Venous thromboembolism (VTE) refers to a blood clot that starts in a vein. As many as 600,000 VTE events occur each year in the United States. There are two types:
- Deep vein thrombosis (DVT) Deep vein thrombosis is a clot in a deep vein, usually in the leg or pelvis. DVT sometimes affects the arm or other veins.
- Pulmonary embolism (PE) A pulmonary embolism occurs when a clot breaks free from a vein wall, travels to the lungs and then blocks some or all of the blood supply. Blood clots originating in the thigh are more likely to break off and travel to the lungs than blood clots in the lower leg or other parts of the body.
What causes venous thromboembolism?
Deep vein thrombosis forms in the legs when something slows or changes the flow of blood. The most common triggers for VTE are surgery, injury, cancer, immobilization and hospitalization.
In women, pregnancy and the use of hormones, such as oral contraceptives or estrogen for menopause symptoms, can also play a role.
Certain factors increase risk for clotting:
- Age (risk increases as age increases)
- History of blood clots
- Other chronic medical conditions, such as congestive heart failure, kidney disease, lung disease or inflammatory bowel disease
- Recent surgery, fracture or injury involving lower leg or pelvis
- Travel within four weeks, lasting more than four hours
- Genetic causes of excessive blood clotting (This occurs when there is an inherited or acquired deficiency of certain proteins such as antithrombin III that affect blood clotting.)
Venous thromboembolism is most common in older adults, but it can occur at any age. VTE is rare in children, though.
Read more about VTE risk factors.
- Printable information sheet: What is VTE? (PDF)