DVT, Virchow's Triad, and Pulmonary Emboli

Over 150 years ago Dr. Rudolph Virchow’s recognized 3 factors that lead to an increase in DVT. Injury to the inner (endothelial) wall of the veins is the initial stimulus that activates the clotting cascade under normal conditions. Conditions such as trauma, crush injury, or surgeries such as hip and knee replacements can cause an increased release of the normal factors that trigger this clotting response.

Saccular VeinAlterations in blood flow leading to stagnant flow (stasis) can trigger increased clotting tendencies. This can be caused by inefficient venous return which occurs in veins with incompetent valves or in areas of saccular or aneurismal dilation. Other causes of stagnant flow occur during periods of relative inactivity of the musculovenous pump paralysis during cramped seating conditions (economy class syndrome), in paralyzed patients or in patients confined to bed for long periods. Dehydration is another factor in changing blood flow characteristics and this is why we encourage people to hydrate well and routinely get up and walk around the cabin or do foot exercises during long airplane or car trips.

Hypercoagulable states are conditions where there is a surplus, deficit or imbalance of the normal clotting factors which can accelerate the clotting cascade. This can develop as the result of metabolic influence from certain cancers (Trousseau’s Syndrome), oral contraceptives, hormone replacement therapies, autoimmune diseases (Antiphospholipid antibodies , Lupus Anticoagulant, and Anticoardiolipin antibody) and inflammatory conditions such as Inflammatory Bowel Disease and Nephrotic syndrome. Thrombophilias are another cause of the Hypercoagulable state and are inherited genetic conditions that result from an abnormal concentration or activity of a clotting factor or from a decrease in the activity of normal factors which are responsible for controlling coagulation. Examples of Thrombophilia states are AntiThrombin III deficiency, Protein S deficiency, Protein C Deficiency, Factor V Leiden mutation and Protein C resistance, Prothrombin 20210A mutation, and Factor VIII elevation These conditions are quite rare, however in patients who have had a DVT their frequency can approach 25%. Like all genetic conditions if the abnormal defect is passed on by both parents (homozygous) then even a minor tendency in each of the parents can lead to serious consequences in their children.