The Etiopathogenesis Of Thrombosis

The Etiopathogenesis Of Thrombosis

Describe the etiopathogenesis of thrombosis.
Answer:

Human beings consist of a system in which blood remains in its fluid state during normal condition and this system also act as a guard to stop thrombosis and hemorrhage.

• The primary influence over the formation of a thrombus is known as Virchow’s triad. It consists of endothelial injury, altered blood flow and hypercoagulability of blood.

Thrombosis Endothelial Injury

• Blood vessel integrity is important for maintaining the normal flow of blood.
• Injurytobloodvesselleadstoexposureofthesubendothelial connective tissue which are thrombogenic and plays an important role in initiating hemostasis and thrombosis.
• An endothelial injury that leads to thrombogenesis occurs under diabetes mellitus, myocardial infarction, arterial diseases etc.
• Vascular injury causes loss of epithelium which exposes extracellular material, adhesion of the platelets, the release of tissue factors, and depletion of prostaglandins and plasminogen activators which leads to the formation of thrombus.
• Any of disturbance in the balance of prothrombotic and antithrombotic mechanisms of the endothelium of the vessel influences the local clotting mechanism.
• Endothelial dysfunction can lead to the release of more amount of more procoagulant factors which are plasminogen activator inhibitors, various tissue factors, etc.

Virchow’s triad thrombosis

Thrombosis Altered Blood Flow

• Normal axial flow of blood in it central stream consists of leucocytes and red blood cells. Platelets exist in a slow-moving laminar stream while which is adjacent to the central stream and the peripheral stream consists of slow-moving cell-free plasma close to the endothelial layer.
• Both turbulence and stasis occur in normal axial blood flow and disturb it.
• When the speed of flow of blood slows down blood cells containing platelets marginate toward the periphery and form a pavement close to the endothelium.
• As stasis leads to a higher release of oxygen from the blood, turbulence injures the endothelium which leads to the deposition of platelets and fibrin.
• Turbulence causes the formation of arterial and cardiac thrombi while stasis leads to the formation of venous thrombi.

Thrombosis Hypercoagulability of Blood

• Hypercoagulability is the alteration in the coagulation pathway that leads to thrombosis.
• It occur due to the following changes in the composition of blood:
  • Increase in coagulation factors such as fibrinogen, prothrombin, and factor 7a, 8a and 10a.
  • Increase in platelet count and its adhesiveness
  • Decrease in levels of coagulation inhibitors i.e. antithrombin III, fibrin split products.

Causes of thrombosis

It is divided into two i.e. genetic and acquired factors Some of the genetic factors which predispose to hypercoagulability are:

• Deficiency of anti-thrombotic factors, i.e. anti-thrombin 3, protein C and S and defects in fibrinolysis.
• Increase in prothrombotic factors such as in factor V mutation, high level of factors 7, 9, 11, 8, Von Willebrand factor and fibrinogen.

Some of the acquired factors which predispose to hypercoagulability are:

• Venous stasis: It is due to prolonged immobilization and congestive cardiac failure.
• Increased platelet activation: In cancers, acute leukemias, myeloproliferative disorders, paroxysmal nocturnal hemoglobinuria, prosthetic cardiac valves, atrial fibrillation, etc.
• Due to increased hepatic synthesis of coagulation factors or reduced anticoagulant synthesis due to oral contraceptives and in pregnancy.
• Due to tissue injuries such as in surgery, fractures and extensive burns.