What is it?
Venous thromboembolism (VTE) is a blood clot in the vein. It's related to two life-threatening conditions:
- Deep vein thrombosis (DVT) is a clot in a deep vein, usually in the leg.
- Pulmonary embolism (PE) is a DVT clot that breaks free from a vein wall, travels to the lungs and blocks some or all of the blood supply. Blood clots 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 is the cause?
Blood clots form when something slows or changes the flow of blood in the veins. These clots can form in, or travel to, arteries or veins in the brain, heart, kidneys, lungs and limbs. They can cause heart attack, stroke, damage to the body’s organs or even death.
Clotting is more likely to happen in people who smoke, take estrogens or birth control pills, or have conditions — such as cancer; autoimmune disorders such as lupus; and obesity. It's also more likely in people whose blood is thicker than normal because too many blood cells are made by bone marrow. Recent surgeries, most commonly in the hip, knee or pelvis, also can increase risk.
A genetic, or inherited, source of excessive blood clotting is less common. Genetic defects can occur in the proteins needed for clotting and with the substances that delay or dissolve blood clots.
VTE is most common in adults 60 and older, but they can occur at any age. It's rare in children. Young patients with venous thrombosis usually have strong predisposing factors, such as multiple trauma, leg fractures or indwelling central venous lines.
How often does it occur?
There are about 900,000 VTE cases and 44,000 related deaths a year in the United States. About 2 million people in the United States suffer deep vein thrombosis each year.
While strides have been made to prevent recurrence of VTE, the rate of “unprovoked VTE” (in which the cause is unknown) in low-risk populations has remained unchanged for the last 40 years. In the United States, unprovoked VTE accounts for 80,000–160,000 cases per year, or up to about 18 percent of all VTE cases.
- Printable information sheet: What is VTE?
- What is excessive blood clotting (Hypercoagulation)?
- Family history and heart disease
This content was last reviewed October 2015.