Common Pathway of Coagulation
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Coagulation
- Common Pathway of Coagulation
- Extrinsic Pathway of Coagulation
- Intrinsic Pathway of Coagulation
- Hemophilia A
- Hemophilia B
- Hemophilia C
- Factor V Leiden
- Antithrombin-3 Deficiency
Summary
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Key Points
- Common Pathway of Coagulation
- Common endpoint of both the intrinsic and extrinsic pathways
- Pathway
- Begins with cleavage of Factor X → Xa
- Via intrinsic or extrinsic pathway
- Requires calcium (Ca2+), phospholipid
- Vitamin K-dependent clotting factor
- Inhibited by Warfarin
- Factor Xa blocked by anticoagulants
- LMWH (e.g. dalteparin, enoxaparin)
- stronger activity at Xa than IIa
- Heparin
- equal activity at Xa and IIa
- Direct Xa inhibitors (e.g. apixaban, edoxaban)
- Fondaparinux (synthetic factor Xa inhibitor)
- LMWH (e.g. dalteparin, enoxaparin)
- Independent cleavage of Factor V → Va
- Activated by IIa (thrombin)
- Does not rely on Factor Xa; acts as an independent co-factor
- Binds to platelets and is activated by thrombin
- Degraded by proteins C & S
- Factor V is mutated in Factor V Leiden (causes thrombophilia), which reduces susceptibility to degradation by protein C
- Activated by IIa (thrombin)
- Factors Xa + Va stimulates cleavage of Factor II (prothrombin) → IIa (thrombin)
- Requires calcium (Ca2+), phospholipid
- Vitamin K-dependent clotting factor
- Inhibited by Warfarin
- Factor IIa activity blocked by anticoagulants
- Heparin
- equal activity at Xa and IIa
- LMWH (e.g. dalteparin, enoxaparin)
- stronger activity at Xa than IIa
- DTIs (e.g. argatroban, bivalirudin, dabigatran)
- Heparin
- Factor IIa activity measured by thrombin time (TT)
- Factor IIa (thrombin) stimulates cleavage of Factor I (fibrinogen) → Ia (fibrin)
- Fibrin aggregates → forms fibrin mesh
- Fibrin mesh stabilizes platelet plug to form blood clot
- Fibrin is stabilized by Factor XIIIa (whose formation from XIII is also stimulated by IIa)
- Factor XIIIa is known as fibrin stabilizing factor
- Begins with cleavage of Factor X → Xa