Blood Clot

A double-edged weapon

Blood clotting should never occur except when an injury happens. Otherwise, the blood clot will unnecessarily occlude a blood vessel, depriving tissues of oxygen and nutrients causing their death. This is called ischemia if the occlusion is incomplete or infarction if it is complete. A prime example can be seen in the heart’s blood vessels when a heart attack happens due to a blood clot. Therefore, coagulation is kept in a delicate balance by the action of natural anticoagulants and fibrinolytics.

Anticoagulants are natural proteins found in the blood in an inactive form. They are activated once coagulation occurs to maintain the balance. They act directly on coagulation factors, limiting their activation. Anticoagulants include antithrombin III, protein C, protein S and thrombomodulin.

The fibrinolytic system is concerned with dissolving the blood clot once it serves its purpose as well as getting rid of abnormally formed blood clots -as in healthy blood vessels-. The main fibrinolytic is called plasmin in its active form and plasminogen in its inactive form. One of the most effective therapies in strokes is an activator for this enzyme. Plasmin breaks fibrin down to smaller molecules called fibrin degradation products. The major fibrin degradation product is called D-dimer and is frequently assessed when a deep venous thrombosis is suspected.