Causes of DVT

Deep Vein Thrombosis Program
John C. Lincoln Deer Valley Hospital

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Phoenix, AZ 85027
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causes of dvt
What causes DVT: In a deep-vein blood clot, clotting agents called "platelets" (shown in turquoise) attract each other as they pass through the bloodstream. Platelets build up and block red blood cells from carrying nutrients to surrounding tissues.

Also known as deep vein thrombosis, DVT is a condition involving blood clots in veins situated deep within legs. DVT affects between 2 and 3 million Americans every year. Among them, just 600,000 receive treatment.

Most frequently, DVT causes leg pain, swelling and skin discoloration — or redness. Frequently, these DVT symptoms show up in just one leg. For example, it is not uncommon for air travelers to notice one leg is swollen or painful after a long flight.

Primary DVT Causes

Generally speaking, DVT causes can be both genetic and behavioral. For example, having a family history of parents or siblings suffering from blood clots, or having blood that coagulates easily, can increase your DVT risk. An undiagnosed clotting disorder can put you at risk of DVT, as well. Behavior-related causes of DVT include smoking and obesity.

Other contributing DVT causes include:

  • Surgery or traumatic injury
  • Cancers and their treatments, both of which may adversely affect the blood's ability to clot
  • Other serious illness, such as congestive heart failure, heart attack, stroke or sepsis
  • Varicose veins
  • People who are pregnant, taking oral contraceptives or incurring other hormonal changes
  • Third trimester pregnancy and immediately following delivery
  • Contraceptives/estrogen therapy; this risk increases in smokers

Other DVT Risk Factors

In terms of events that may "trigger" the condition, specific DVT causes revolve around extended sedentary behavior. When we're healthy, our muscles help our blood keep moving. But when we're not moving around, blood tends to pool and clot at the lowest part of the body. Blood pressure is relatively low in the veins that return blood to the heart.

Prolonged bed rest due to illness — and recovery from surgery or trauma — are common causes of DVT. Likewise, sitting on an airplane for six or more hours without moving around is one of the leading causes of deep vein thrombosis. For this reason, DVT is often referred to as "economy class syndrome."

People who have had injury to their veins — due to trauma, athletic accidents or surgery — also face higher DVT risk.

What makes deep vein thrombosis especially dangerous? If untreated, a piece of a deep-vein blood clot can break loose and travel to the lungs, causing pulmonary embolism — a condition that claims approximately 60,000 Americans annually. Potentially, DVT can cause an ulcer or varicose veins.