What is a Blood Clot or “Thrombus”?

The National Institutes of Health define a “blood clot” as the sticking together of blood platelets, proteins, and cells that forms on the wall of a blood vessel or in the heart. Blood clots can be beneficial when they form in response to an injury, to plug a hole in a blood vessel; however, some clots form inside the vein and do not dissolve naturally.

What is Deep Vein Thrombosis (DVT)?

A DVT is the formation of a blood clot within a deep vein of the body, most commonly in the leg. Between 350,000 and 600,000 people develop DVT each year in the US (1). DVT affects men and women at all ages and our risk tends to increase as we get older.

People who develop DVT often have one or more of the following risk factors:

  • Recent major trauma (for example, bone fractures)
  • Recent major surgery
  • Cancer
  • Limited mobility due to medical illness, paralysis or other condition
  • Pregnancy
  • Hormonal treatments (for example, birth control pills)
  • Medical disorders of the blood clotting system (often inherited)

Two-thirds of DVT cases occur in people who are hospitalized for surgery or a medical illness.

What problems does DVT cause?

There are three common consequences of a DVT episode:

  1. A DVT can break free and flow within the bloodstream to the lungs. This complication is called Pulmonary Embolism or PE. When PE occurs, it is often fatal. PE causes over 100,000 deaths each year in the U.S.
  2. Patients with DVT often experience pronounced pain, swelling, cramping, and/or tenderness of the involved leg during the initial episode.
  3. DVT survivors often experience long-term pain, swelling, heaviness, fatigue, skin changes, and/or open sores on the legs, a complication called the Post-Thrombotic Syndrome (PTS). PTS develops in approximately 40% of patients with a first episode of DVT, which is between 50,000 and 100,000 patients per year (2).

If you have been diagnosed with PTS:

About 30% of DVT patients will later develop additional DVT episodes (3)

  1. The Surgeon General’s Call to Action to Prevent Deep Vein Thrombosis and Pulmonary Embolism. U.S. Department of Health and Human Services report, 2008.
  2. Kahn SR, Shrier I, Julian JA, et al. Determinants and time course of the postthrombotic syndrome after acute deep venous thrombosis. Ann Intern Med 2008; 149(10):698-707.
  3. Prandoni P, Lensing A, Cogo A, et al. The long term clinical course of acute deep venous thrombosis. Ann Intern Med 1996; 125:1-7.
  4. Kearon C, Kahn SR, Agnelli G, Goldhaber SZ, Raskob G, Comerota AJ. Antithrombotic therapy for venous thromboembolic disease. American College of Chest Physicians Evidence-Based Clinical Practice Guidelines (8th Ed). Chest 2008; 133:454S-545S.