Deep Vein Thrombosis: What It Is And How To Prevent It


by Gary Towle, M.D.

DVT (deep vein thrombosis) is a common but serious medical condition that affects approximately two million Americans each year. DVT occurs when a blood clot forms in one or more of the deep veins, usually in the legs or pelvis. This disorder may result in serious complications such as a pulmonary embolism (PE) and possibly even death if it is not diagnosed and treated promptly and appropriately. A pulmonary embolism occurs when one of the deep vein clots breaks loose and travels up to the lungs. Pulmonary emboli kill approximately 300,000 people per year, more than breast cancer, AIDS, and motor vehicle accidents combined. It is the leading cause of preventable deaths in U.S. hospitals.

Causes and Risk Factors
Almost all DVTs form under some combination of three conditions: 1) Deep vein inflammation or injury, 2) Increased risk of blood clot formation, and 3) immobilization. Specific risk factors for developing DVT and possibly a PE include a family history of blood clotting disorders; age over 40; hormone treatment such as birth control pills or hormone replacement therapy; smoking; obesity; leg swelling; some serious medical conditions such as cancer, congestive heart failure, or pneumonia; and prolonged immobilization such as long trips or lengthy hospital stays.

Approximately half of the individuals with DVT have no symptoms while the other half exhibit findings such as swelling, redness, tenderness, or discoloration of the affected extremity (usually a leg but rarely may involve an arm as well). The symptoms of a DVT are often unilateral while muscle soreness from excessive exercise would be more generalized. A small pulmonary embolism may have minimal or no symptoms but the larger PEs are associated with symptoms of chest pain (usually worse with deep breaths), shortness of breath, rapid heart rate, or unexplained cough. Coughing up blood is an especially ominous sign.

Ultrarunning and DVT
Ultrarunners are especially susceptible to DVTs because extended periods of strenuous exercise are often followed by prolonged periods of inactivity because of exhaustion and fatigue as well as muscle soreness and stiffness. In addition many ultrarunners have traveled long distances from home to the race site and often have a long car ride or plane flight to return home shortly after the event. Many runners experience swelling of their feet and legs. Some runners may not be properly hydrated. There is also speculation that hours of running up and down trails may initiate tiny clots as the result of minor trauma to the muscles of the legs.

Preventative Measures
Many episodes of DVT and PE can be avoided by taking a few simple precautions. Elevate your legs if there is any evidence of swelling. If you have a long car or plane trip ahead of you, it is a good idea to get up and walk around as often as possible, but at least hourly. While seated, gently move your feet, ankles, calves, and thighs to stimulate circulation and avoid blood pooling. Compression stockings may help. Stay well hydrated. Aspirin is actually a mild blood thinner and may be taken an hour or so before the anticipated extended trip. But most important of all, if you have unusual swelling, redness, or tenderness in your legs or sudden chest discomfort, shortness of breath, or unexplained coughing with or without bloody sputum, seek medical evaluation and treatment promptly as DVT and PE are preventable and treatable disorders – but can be debilitating or deadly if not recognized early.

Gary Towle is an emergency room physician and has been on the Western States 100 Board of Trustees for more than 25 years.




  1. Thank you for your article! Few questions: how does a deep vein injury/inflamation present itself (also, I guess another question – how is a deep vein injury caused)? Also, is there any correlation/causation between excessive/severe foot/leg cramping during a race/run and DVT?

  2. charlie lee on

    i am curious about the incidence of DVT in ultrarunners. Yours comments about causes appear to be more common sense. Are there any study done?.