Deep venous thrombosis (DVT) is a condition that occurs when a blood clot, or thrombus, forms in a major vein, usually in the leg. The clot can partially or completely block off the blood flow through that vein. Veins are the vessels that return the blood to the heart, so a blockage of that circulation can lead to poor emptying of blood in the extremity, causing swelling and pain. If the clot is not treated, all or part of it can break off and travel up to the heart, through it, and into the lungs. In the lungs, it can obstruct blood supply with life-threatening consequences. This is known as pulmonary embolism (PE).
Massive pulmonary embolism attributed to DVT causes over 300,000 deaths in the United States each year. That’s more than deaths from breast cancer and HIV disease combined. PE is the leading cause of preventable in-hospital mortality.
There are certain people who are more at risk than others to develop DVT. Age plays a major role. Although a blood clot can develop in anyone, the older you are, the greater the likelihood. Additional risk factors include immobilization due to hospitalization, recent surgery, pregnancy and the first weeks postpartum, and long air or car trips. Other conditions which are known to have a higher risk include cancer, stroke, heart failure, and varicose veins. Injuries such as lower extremity fractures can also cause blood clots to form. Finally, there are conditions which make the blood more likely to coagulate or clot. These include certain blood disorders that may be inherited and medications such as birth control pills or estrogens. The more risk factors an individual has, the more likely he or she is to develop DVT.