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Deep Vein Thrombosis

What Causes Deep Vein Thrombosis?

Thursday, June 14, 2012 - 13:04

Contributing Author: Guy Slowik FRCS

Veins are thin-walled blood vessels that carry blood from the body tissues back to the heart. In order to move the blood from the legs toward the heart, the leg muscles squeeze the deep veins, forcing the blood upward.

Deep vein thrombosis is the result of three principal factors (described by Dr. Virchow in the 1860';s):

  1. Reduced or stagnant blood flow in deep veins (venous stasis).
  2. Injury to the blood vessel wall.
  3. An increase in the activity of those substances in the blood that are part of the normal clotting mechanism, a condition called hypercoagulability (which means a more active clotting state).

A number of factors can bring about these conditions, thus increasing the possibility of developing DVT. These include:

  • Immobilization, such as lying in bed following surgery
  • Having undergone a surgical procedure
  • Having been subjected to major trauma
  • Increasing age
  • Malignancy (cancerous tumor)
  • Heart failure
  • A previous bout with deep vein thrombosis
  • Pregnancy
  • The use of oral contraceptives

Need To Know:

Surgical procedures that are most often associated with deep vein thrombosis are:

  • Major pelvic or abdominal surgery, especially for malignancy (cancer)
  • Orthopedic operations involving the hip and knee
  • Neurosurgical procedures

The following factors also put people at greater risk of developing a blood clot:

  • Prolonged immobilization (such as on a long car or airplane trip) - sitting for long periods (4 hours or more) reduces circulation in legs by 50 percent.
  • Diabetes (a disorder in which the body can not make use of sugars and starches in a normal way), which damages blood vessels.
  • Obesity - weight puts pressure on veins, causing them to weaken.
  • Childbirth - physical strain of childbirth puts pressure on deep veins, causing them to weaken.
  • Tobacco smoking - damages blood vessels and doubles the risk of thrombosis.

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