An Introduction to Understanding Thrombosis

This section introduces haemostasis, the coagulation cascade, venous and arterial thrombi and thrombus formation

In this section:

Play the video below to see Professor Graham Turpie highlighting the information available in this section

What is haemostasis?

  • Haemostasis is the normal physiological response preventing significant blood loss after vascular injury
  • The process depends on an intricate series of events involving platelets, other cells, and the activation of specific blood proteins, known as coagulation factors
  • When blood vessel injury occurs, physiological haemostasis is triggered and the coagulation process begins
  • Haemostasis serves to maintain the integrity of the circulatory system; however, the process can become imbalanced, leading to significant morbidity and mortality
  • Knowledge of the haemostasis process is important in understanding the major disease states associated with thrombosis

Click here to find out more about haemostasis

The coagulation cascade

  • The coagulation process that leads to haemostasis involves a complex set of reactions involving approximately 30 different proteins
  • These reactions convert fibrinogen to fibrin, which, together with platelets, forms a stable thrombus
  • Several coagulation cascade models have been proposed, including the intrinsic and extrinsic pathway model and the more recent cell-based model
  • Building on these models, ongoing research has elucidated a role for other components of the coagulation process, including microparticles and the protein P-selectin
  • An inherited or acquired imbalance in the coagulation system that leads to an increased risk of thrombosis is called thrombophilia
  • Approximately one in three patients with VTE has an inherited thrombophilia

Click here to find out more about the coagulation cascade

Venous thrombi

  • Formation of a thrombus within a vein is known as a venous thrombosis
  • If the thrombus breaks loose and travels through the circulatory system, it is known as an embolus
  • Venous thrombi manifest mainly as DVT and PE
    • DVT is the most common type of VTE, but patients with DVT are also at risk of PE, which can potentially be life-threatening
  • VTE is associated with cancer, trauma and surgery, and several pre-disposing risk factors, including pregnancy, obesity and immobility, have been identified
  • VTE can also lead to serious long-term complications, including PTS and CTEPH

Click here to find out more about venous thrombosis

Thrombus formation

  • Haemostasis is necessary for survival, but the pathological formation of a thrombus poses significant health risks
  • A pathological thrombus, formed when there is an imbalance in the blood coagulation system, can potentially obstruct blood flow, leading to a number of serious health conditions
  • Two different types of thrombi can be formed:
    • Arterial thrombi
    • Venous thrombi
  • The pathologist Rudolph Virchow postulated that thrombus formation and propagation resulted from abnormalities in three areas, collectively known as Virchow’s triad
  • It is now possible to quantify some of the factors that are associated with an increased risk of VTE and other cardiovascular diseases, and of stroke in patients with AF

Play the video below to watch the formation of a thrombus

Approval No.: G.MKT.GM.XA.08.2016.1048

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