Virchow’s Triad
🔹Virchow’s Triad – refers to the 3 primary factors which can promote thrombus formation, these are useful to consider when thinking about the possible causes in a particular situation and it includes:
1) Endothelial injury
2) Stasis, turbulence or abnormal blood flow
3) Blood hypercoagulability.
➡️ The list of examples of causes of each is not intended to be exhaustive :
📌 ENDOTHELIAL INJURY
Physical loss of endothelium leads to exposure of subendothelial extra-cellular matrix, adhesion of platelets, release of tissue factor, and local depletion of PGI2 and plasminogen activators.
– endothelial injury
🔸myocardial infarction
🔸cardiac valve disease
🔸endotoxins
🔸vasculitis
🔸ulcerated atheromas
🔸iatrogenic: venous catheters, etc.
📌 ABNORMAL BLOOD FLOW
Turbulence can cause endothelial injury which is in itself a major influence for thrombosis. Apart from that abnormal blood flow can:
1) Disrupt laminar flow and bring platelets into contact with the endothelium
2) Prevent dilution of activated clotting factors by fresh-flowing blood
3) Retard the inflow of clotting factor inhibitors and permit the buildup of thrombi
4) Promote endothelial cell activation, resulting in local thrombosis, leukocyte adhesion, etc.
– disturbance of flow: slow and/or turbulent
🔸iatrogenic: venous catheters, etc.
🔸immobility
🔸vascular stasis: varicose veins, arterial 🔸aneurysms
🔸chemotherapy
🔸sepsis
📌 HYPERCOAGULABILITY
It can be primarily due to a genetic disorder and secondarily due to some acquired problems.
hypercoagulability
– primary thrombophilia
🔸factor V Leiden
🔸protein S deficiency
🔸protein C deficiency
🔸antithrombin III deficiency
– acquired thrombophilia
🔸malignancy
🔸myeloproliferative disorders
🔸pregnancy, OCP, HRT
🔸obesity
🔸nephrotic syndrome
📍The primary causes are:
1) mutation of factor V gene a/k/a factor V Leiden
2) mutation of prothrombin gene
3) anti-thrombin III deficiency
4) protein C deficiency
5) protein S deficiency
📍The secondary causes are:
1) prolonged immobilization
2) myocardial infarction
3) atrial fibrillation
4) cancer
5) prosthetic cardiac valves
6) heparin induced thrombocytopenia
7) hyperestrogenic states e.g. pregnancy / OCP use
8) smoking
9) sickle cell anemia