Causes and types of thrombosis

1. Hemostasis vs Thrombosis

• Hemostasis = normal coagulation; thrombosis = pathological coagulation. Both involve vascular wall, platelets, coagulation cascade.
• Hemostatic sequence: vasoconstriction (endothelin) → primary hemostasis (platelet adhesion/aggregation) → secondary hemostasis (tissue factor + FVII → thrombin → fibrin) → anti-thrombotic counter-regulation (thrombomodulin, tPA).

2. Virchow’s Triad

Factor	Detail
Endothelial injury	Most dominant; MI scar, endocarditis, ulcerated plaque. Denuding (HTN, endotoxin, turbulence) vs non-denuding (smoking, hypercholesterolemia, irradiation)
Abnormal flow	Stasis (aneurysm, AF, mitral stenosis, hyperviscosity) / turbulence → platelet contact + clotting factor build-up
Hypercoagulability	Primary: Factor V Leiden, prothrombin mutation. Secondary: OCP, cancer (mucin), old age, antiphospholipid syndrome, immobilization

3. Types of Thrombi

• White (sedimentation): fibrin + platelets; arterial / heart chambers; endothelial injury.
• Red (stasis): all blood elements, RBC-rich; veins.
• Composite (propagating): white head + red tail (arteries).
• Laminated: aneurysms; alternating platelet/fibrin (white) + RBC (red) = lines of Zahn (thrombosis in flowing blood).
• DIC: thrombi form + immediately embolize.

4. Localization

• Mural: heart — atrium (mitral stenosis, AF, left HF), ventricle (MI), valves (vegetation = infective; verruca = non-infective endocarditis).
• Arterial (white): coronaries, femoral, cerebral → ischemia/infarction.
• Venous (red): DVT (→ PE), portal vein (cirrhosis), Trousseau migratory thrombophlebitis.

5. Fate of Thrombus

• Propagation, dissolution (fibrinolysis; older thrombi resistant; tPA/streptokinase), embolization, organization → recanalization.

💡 High-yield: Virchow’s triad = endothelial injury (dominant) + stasis/turbulence + hypercoagulability. Arterial = white (platelet-rich, injury); venous = red (RBC-rich, stasis). Lines of Zahn = thrombus formed in flowing blood (antemortem). Fates: propagate, dissolve, embolize, organize/recanalize.