Virchow Triad
The Virchow Triad – also known as Virchow’s Triad – describes the formation processes underlying the formation of a thrombosis. There are 3 mechanisms that play a decisive role in the formation of thromboses.
- Damage to the vascular endothelium: Vessels (veins and arteries) are lined by so-called endothelium.
The endothelium can be imagined as a thin layer that completely covers the vessel from the inside. It fulfils important tasks, one of which is to ensure a good blood flow. It is smooth and contains important factors of blood clotting.
The endothelium is damaged by trauma or inflammation, for example as a result of various diseases such as diabetes or high blood pressure.
- Reducing the blood flow velocity and changing the hemodynamics: One must imagine that the blood flows very regularly in the vessels. In technical terminology, this type of flow is called laminar.Changes in the vessel can lead to turbulent flow, which causes damage to the vessel wall due to shear forces. The counter flow causes the blood to flow more slowly.
Factors that reduce the speed of the blood flow include Immobilization or external pressure on a limb.
- Change in blood composition: When the blood composition changes and the blood becomes tougher (more viscous), blood clots (thrombi) can form more easily. The composition of the blood is altered, for example, in congenital thrombophilia (tendency to clot) or in the course of various diseases. This results in an increased readiness to clot, which is known as hypercoagulability.
Thrombosis causes cancer
Approximately 20% of all venous thromboembolism occurs at the base of a cancerous disease. It cannot be denied that cancer patients have a significantly increased risk of thrombosis compared to the healthy rest of the population. This is due to various reasons.
First of all, there are cancers that directly affect the hematopoietic system and thus also the cells involved in clotting. On the other hand, due to their localization, tumors also change the flow conditions of the blood and thus intervene in the normal, physiological circulation. However, the keyword “Paraneoplastic Syndrome” is much more important.
This term refers to a constellation of symptoms or findings that results from a cancer disease but is not the direct consequence of local tumor growth or metastases. But how exactly can this be imagined? The tumor not only causes damage by growing somewhere in the body and displacing or impairing the surrounding structures and organs, but also has a metabolism that is sometimes very harmful.
Metabolic products are produced, or even in some cases hormones, which intervene in the physiological (natural) system of the human organism. For example, an increased tendency to clot (thrombophilia) or even an antiphospholipid syndrome can develop on the basis of such metabolic products. For example, tumors release coagulation-promoting substances such as tissue thromboplastin.
Another important factor that increases the risk of thrombosis in cancer patients is therapy. Surgery leads to immobilization of the patient, which can increase the risk of thrombosis. There are also chemotherapeutic and other drugs used in cancer therapy that are also associated with an increased risk of thrombosis.
The consequences are thromboses and thrombembolism, which can sometimes be fatal. Thrombosis or thromboembolism is the second most common cause of death in cancer patients. However, the risk of death varies considerably between the different types of cancer.
For example, the risk is particularly high for glioblastoma. Furthermore, the risk is considerably influenced and increased by immobilization, advanced disease, lack of fluid and the presence of metastases. Unfortunately there is no proper prophylaxis.
Cancer patients should try to avoid dehydration and long periods of immobilization. Furthermore, it is recommended to strictly avoid risk factors such as smoking or high blood pressure. However, a prophylactic administration of anticoagulant medication is controversially discussed and is always an individual decision. One must weigh up the risk of thrombosis and the supposedly increased risk of tumor bleeding due to the medication.
