Deep vein thrombosis pathophysiology

Editors-in-Chief: C. Michael Gibson, M.S., M.D. Associate Editor-In-Chief: Ujjwal Rastogi, MBBS [mailto:urastogi@perfuse.org]

Overview
Deep venous thrombosis (DVT) mainly affects the large veins in the lower leg and thigh. The clot can block blood flow and cause swelling and pain. When a clot breaks off and moves through the bloodstream, this is called an embolism. An embolism can get stuck in the brain, lungs, heart, or other area, leading to severe damage.

Blood clots may form when something slows or changes the flow of blood in the veins.

Pathophysiology
Rudolf Virchow noted several factors affecting the clot formation, which are as follows:

1).Alterations in blood flow (stasis) : Blood flows throughout the circulatory system, without significantly stopping or slowing any where. In certain pathological conditions (as in heart failure) where the blood flow slows down or stops, it causes This increases the risk of clot formation and form microthrombi, which further grow and propagate.
 * a) Increase in platelet to endothelium contact
 * b) Decrease the dilution of clotting factors

2).Injury to the vascular endothelium : Intrinsic or secondary to external trauma (Eg. catheterization) can cause intimal damage and stimulates clot formation. See Coagulation

3).Alterations in the constitution of blood (hypercoagulability) :It is the propensity to develop thrombosis due to an abnormality in the system of coagulation.

These three conditions are collectively known as Virchow's triad and lead to intravascular coagulation, forming a mass of red blood cells, leukocytes, and fibrin.

More DVT's occur in the left leg than in the right, because the right common iliac artery compresses the left common iliac vein.(see May-Thurner syndrome)

Thrombi usually develop first in the calf veins, "growing" in the direction of blood flow. DVTs are distinguished as being above or below the popliteal vein. Very extensive DVTs can extend into the iliac veins or the inferior vena cava. The risk of pulmonary embolism is higher in the presence of more extensive clots.

 This video explains the process of thrombosis.