What is the pathophysiology of DVT?
Deep vein thrombosis (DVT) usually occurs in the lower extremities. The factors that
promote the formation of DVTs are:
* venous stasis
* venous endothelial damage
* states of increased coagulation
(Brashers, 2006)
A thrombus may form near a valve in deep calf veins. This is due to an accumulation of
clotting factors and platelets. The release of tissue thromboplastin and the formation of
thrombin and fibrin will trap RBCs (Berkow & Fletcher, 1987). This clot causes
inflammation which causes more platelet aggregation, thus the clot grows larger and
becomes obstructive.
The exact primary genesis of thrombus formation remains unclear. Endothelial damage
has been postulated as the first step of thrombus formation, however experimental
evidence has not been able to fully support this. Platelet aggregation is involved as
platelets may adhere to morphologically intact endothelium, as opposed to only damaged
endothelium as has been accepted in past theories of thrombus formation. Most thrombi
become adherent to the vein wall by spindled shape cells which resemble endothelial
cells. A continuous process involving organization and thrombus formation then occurs
(May, 2001).
Wikipedia (n.d) states that three things can affect the formation of a clot. The flow rate
of the blood, the viscosity of the blood and the quality of the vessel wall. These three
things make up Virchow’s triad. Deep vein thrombosis (DVTs) more often occurs in the
left leg possible because of the right common iliac artery overlays the left common iliac
vein and can compress it, leading to stasis of the blood. DVTs can extend into the iliac
veins or inferior vena cava if they are very large. Highly extensive clots also puts the
patient at a higher risk of developing pulmonary embolism (Wikipedia, n.d.).
References
Berkow, R. & Fletcher, A.J. (1987). The Merck manual. (pp. 565-567). Rahway, NJ.:
Merck Sharp & Dohme.
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. (pp. 1081-1146). St. Louis, MO: Elsevier Mosby.
May, C. (2001). Management of venous thrombolytic disease in the lower limb.
Emergency Medicine, 13, 211-223.
Pulmonary Embolism. (n.d). Retrieved on July 2, 2008 from
http://en.wikipedia.org/wiki/Deep_vein_thrombosis#Signs_and_symptoms