Risk factorsBy Mayo Clinic staff
CLICK TO ENLARGE
|Blood clot in leg|
Although anyone can develop blood clots leading to pulmonary embolism, certain factors can increase your risk.
Blood clots are more likely to form in your legs during periods of inactivity, such as:
- Bed rest. Being confined to bed for an extended period after surgery, a heart attack, leg fracture or any serious illness makes you far more vulnerable to blood clots forming in your legs.
- Long journeys. Sitting in a cramped position during lengthy plane or car trips slows the current of blood flow in your veins, which contributes to the formation of clots in your legs.
Older people are at higher risk of developing clots. Factors include:
- Valve malfunction. Tiny valves located every few inches within your larger veins keep your blood moving in the right direction. However, these valves tend to degrade with age. When they don't work properly, blood pools and sometimes forms clots.
- Dehydration. Older people are at higher risk of dehydration, which may thicken the blood and make clots more likely.
- Medical problems. Older people are also more likely to have medical problems that expose them to independent risk factors for clots — such as joint replacement surgery, cancer or heart disease.
It is rare for children to develop DVT or VTE.
You're at higher risk of experiencing future clots if you or any of your family members have had blood clots in the past. This may be due to inherited disorders of clotting that can be measured in specialty clotting labs. Be sure that your doctor knows about your family history so that appropriate tests can be done to check for an inherited clotting disorder.
Surgery is one of the leading causes of problem blood clots, especially joint replacements of the hip and knee. During the preparation of the bones for the artificial joints, tissue debris may enter the bloodstream and help cause a clot. Simply being immobile during any type of surgery can lead to the formation of clots. The risk increases with the length of time you are under general anesthesia.
You may be more likely to develop blood clots with these conditions:
- Heart disease. High blood pressure and cardiovascular disease make clot formation more likely.
- Pregnancy. The weight of the baby pressing on veins in the pelvis can slow blood return from the legs. Clots are more likely to form when blood slows or pools.
- Cancer. Certain cancers — especially pancreatic, ovarian and lung cancers — can increase levels of substances that help blood clot, and chemotherapy further increases the risk. Women with a history of breast cancer who are taking tamoxifen or raloxifene also are at higher risk of blood clots.
- Previous blood clots. If you've experienced DVT or VTE in the past — for any reason — you're at increased risk of developing the condition again.
Certain lifestyle factors increase your risk of blood clots, including:
- Smoking. For reasons that aren't well understood, tobacco use predisposes some people to blood clot formation, especially when combined with other risk factors.
- Being overweight. Excess weight increases the risk of blood clots — particularly in women who smoke or have high blood pressure.
- Supplemental estrogen. The estrogen in birth control pills and in hormone replacement therapy can increase clotting factors in your blood, especially if you smoke or are overweight.
- Pulmonary embolism. National Heart, Lung, and Blood Institute. http://www.nhlbi.nih.gov/health/dci/Diseases/pe/pe_all.html. Accessed Aug. 3, 2011.
- Thompson BT, et al. Overview of acute pulmonary embolism. http://www.uptodate.com/home/index.html. Accessed Aug. 3, 2011.
- Kline JA, et al. Pulmonary embolism and deep vein thrombosis. In: Marx JA, et al. Rosen's Emergency Medicine: Concepts and Clinical Practice. 7th ed. Philadelphia, Pa.: Mosby Elsevier; 2010. http://www.mdconsult.com/books/about.do?about=true&eid=4-u1.0-B978-0-323-05472-0..X0001-1--TOP&isbn=978-0-323-05472-0&uniqId=230100505-57. Accessed Aug. 3, 2011.
- Bauer KA, et al. Overview of the causes of venous thrombosis. http://www.uptodate.com/home/index.html. Accessed Aug. 3, 2011.
- Deep vein thrombosis. American Academy of Orthopaedic Surgeons. http://orthoinfo.aaos.org/topic.cfm?topic=A00219. Accessed Aug. 3, 2011.
- Weitz JI. Pulmonary embolism. In: Goldman L, et al. Goldman's Cecil Medicine. 24th ed. Philadelphia, Pa.: Saunders Elsevier; 2011. http://www.mdconsult.com/das/book/body/191371208-2/0/1492/0.html#. Accessed Aug. 3, 2011.
- Rosenow EC (expert opinion). Mayo Clinic, Rochester, Minn. Aug. 21, 2011.
- Troncales FD, et al. Pulmonary embolism. In: Ferri FF. Ferri's Clinical Advisor 2012: 5 Books in 1. Philadelphia, Pa.: Mosby Elsevier; 2012. http://www.mdconsult.com/books/linkTo?type=bookPage&isbn=978-0-323-05611-3&eid=4-u1.0-B978-0-323-05611-3..00025-2--sc0355. Accessed Aug. 16, 2011.
- General nuclear medicine. Radiological Society of North America. http://www.radiologyinfo.org/en/info.cfm?PG=gennuclear. Accessed Aug. 16, 2011.
- Catheter angiography. Radiological Society of North America. http://www.radiologyinfo.org/en/info.cfm?PG=Angiocath. Accessed Aug. 16, 2011.
- Lip GY, et al. Patient information: Deep vein thrombosis (DVT). http://www.uptodate.com/home/index.html. Accessed Aug. 16, 2011.
- Deep vein thrombosis. National Heart, Lung, and Blood Institute. http://www.nhlbi.nih.gov/health/dci/Diseases/Dvt/DVT_All.html. Accessed Aug. 16, 2011.
- FDA expands use of Xarelto to treat, reduce recurrence of blood clots. U.S. Food and Drug Administration. http://www.fda.gov/NewsEvents/Newsroom/PressAnnouncements/ucm326654.htm?source=govdelivery. Accessed Jan. 2, 2013.