The causes of thrombus formation are summarized in the Virchow triad:
- I. Disruption or alteration of the vessel wall.
These can be caused by e.g.
- trauma
- arteriosclerosis
- great mechanical stress
- ischemia
All of the above factors can lead to damage to the endothelium, resulting in a lack of antithrombogenic substances and thus thrombin formation (Nennstiel 2019).
- II. disturbance of hemodynamics
Disorders of hemodynamics include a:
- Slowing of blood flow due to, e.g.
- Compression of the vessels
- Enlargement of the vessels (e.g., in varices)
- increase of hematocrit
- Increase of the viscosity of the blood
- Obstruction of the lumen
- Vortex formation, especially at passage obstacles, vessel branches and aneurysms
- Acceleration of blood flow due to, for example, hypertension, in which platelets are pressed against the vessel wall (Nennstiel 2019)
- III. disturbance of the blood composition
Blood composition disorder may occur due to:
- Increase in platelet count due to, e.g.
- Neoplasia of the hematopoietic system. This may lead to increased platelet activation.
- Increase in cell count due to e.g.
- Decrease in serum. Increased blood viscosity may lead to slowing of flow.
- Neoplasms
- Paraneoplastic syndrome in e.g.
- metastatic carcinoma. In this case, the carcinoma itself produces increased procoagulant substances.
- Hereditary disorders, e.g.
- Factor V Leiden mutation
- Postoperative or after injuries
- In this case, there are more clotting factors than normal in the blood due to tissue damage (Nennstiel 2019).
- Medication due to e.g. anticonceptives
- During pregnancy (Nennstiel 2019).
A deposition thrombus forms when blood flow is maintained and is caused by, for example, an atherosclerotically altered arterial wall, in inflamed vessels (e.g., in arteritis, thrombophlebitis), aneurysms, in mitral valve defects in the left atrium, in myocardial infarctions, etc. (Weimann 2002).
The risk of formation of a deposition thrombus in the form of myocardial infarction or apoplexy is significantly increased during bacterial or viral infections. Secretion thrombi also contribute to the high mortality in the context of sepsis (Kasper 2015).