What is the pathophysiology of DVT?
Three factors are known to promote venous thrombosis:
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Venous stasis, such as with immobility, CHF, or in elderly individuals.
Vessel wall injury, such as in trauma or that which may occur with medications.
Hypercoagulable states, such as in inherited disorders, malignancy, pregnancy, or in
individuals taking oral contraceptives or hormone replacement therapy (Brashers, 2006;
Schreiber, 2007).
These three mechanisms are often referred to as the Virchow triad (Schreiber, 2007).
Millions of tiny injuries occur within blood vessels each day, resulting in millions of microthrombi
being formed and lysed in a functional hemostatic balance (Feied, 2005). “In practical terms, venous
thrombosis is best understood as the activation of coagulation in areas of reduced blood flow”
(Schreiber, 2007, scn. 2). The initiating event in venous thrombosis is platelet adhesion (Feied,
2005). Venous stasis promotes accumulation of clotting factors and platelets. The inflammatory
response promotes further platelet aggregation and the thrombus increases in size (Brashers, 2006).
Thrombus usually forms behind valve cusps or at points of vein branching, typically in the calf of the
affected individual (Hoffer, 2007). Dilation of the vein may expose the subendothelium by disruption
of the endothelial cell wall, activating the adherence of platelets to the area (with the help of
vonWillebrand factor or fibrinogen in the vessel wall; Hoffer, 2007). Activation of neutrophils and
platelets follows, with the subsequent release of both procoagulant mediators and inflammatory
mediators (Hoffer, 2007). This sets off a cascade of cells arriving, including leukocytes, and a
thrombus composed of platelets, leukocytes, and fibrin develops (Hoffer, 2007).
Most thrombi will dissolve on their own without treatment, but untreated DVT is associated with a
high risk of pulmonary embolism (PE; Brashers, 2006).
References
Brashers, V. L. (2006). Alterations of cardiovascular function. In McCance, K. L., & Huether, S. E.
(Eds.), Pathophysiology: The Biologic Basis for Disease in Adults and Children (5th ed., pp. 1081-1146).
Elsevier Mosby: St Louis.
Feied, C. (2005). Deep venous thrombosis. Retrieved June 30, 2008, from
http://www.emedicine.com/med/topic2785.htm#section~introduction
Hoffer, E. K. (2007). Deep venous thrombosis, lower extremity. Retrieved June 30, 2008, from
http://www.emedicine.com/radio/topic773.htm
Schreiber, D. (2007). Deep venous thrombosis and thrombophlebitis. Retrieved June 30, 2008, from
http://www.emedicine.com/emerg/topic122.htm