Fibrinolysis
Fibrinolysis is a process that prevents blood clots from growing and becoming problematic. Primary fibrinolysis is a normal body process, while secondary fibrinolysis is the breakdown of clots due to a medicine, a medical disorder, or some other cause.[1]
In fibrinolysis, a fibrin clot, the product of coagulation, is broken down.[2] Its main enzyme plasmin cuts the fibrin mesh at various places, leading to the production of circulating fragments that are cleared by other proteases or by the kidney and liver.
Physiology
Plasmin is produced in an inactive form,
Measurement
Plasmin breaks down fibrin into soluble parts called fibrin degradation products (FDPs). FDPs compete with thrombin, and thus slow down clot formation by preventing the conversion of fibrinogen to fibrin. This effect can be seen in the thrombin clotting time (TCT) test, which is prolonged in a person that has active fibrinolysis.
FDPs, and a specific FDP, the
Testing of overall fibrinolysis can be measured by a
Role in disease
Few
However, acquired disturbance of fibrinolysis (hyperfibrinolysis), is not uncommon. Many trauma patients have an overwhelming activation of tissue factor and thus massive hyperfibrinolysis.[6] Hyperfibrinolysis may occur in other disease states. It could lead to massive bleeding if not diagnosed and treated early enough.
The fibrinolytic system is closely linked to control of inflammation, and plays a role in disease states associated with inflammation. Plasmin, in addition to lysing fibrin clots, also cleaves the complement system component C3, and fibrin degradation products have some vascular permeability inducing effects.
Pharmacology
In a process called
Thrombolysis refers to the dissolution of the thrombus due to various agents while fibrinolysis refers specifically to the agents causing fibrin breakdown in the clot.
Antifibrinolytics, such as aminocaproic acid (ε-aminocaproic acid) and tranexamic acid are used as inhibitors of fibrinolysis. Their application may be beneficial in patients with hyperfibrinolysis because they arrest bleeding rapidly if the other components of the haemostatic system are not severely affected.[8] This may help to avoid the use of blood products such as fresh frozen plasma with its associated risks of infections or anaphylactic reactions.
Fibrinolytic enzymes
- Anistreplase
- Desmoteplase
- Streptokinase
- Nattokinase
- Lumbrokinase
- Serrapeptase
- Papain
- DNase
- Bromelain
- Honokiol
References
External links
- Graphical representation of the fibrinolytic pathway (site not available)