Thrombus

Definition
  • A thrombus is a clotted mass of blood and can occur anywhere in cardiovascular system
Causes
Categorization
  • Thrombi are categorized by location:
  • Mural Thrombi
    • Attached to the wall of the heart chambers or aortic lumen
  • Arterial thrombi
    • Usually occlusive
    • Possess Lines of Zahn: Thrombus has alternate layers of light material (platelets and fibrin) and dark material (RBCs)
  • Venous Thrombi (Phlebothrombosis)
    • Always occlusive
    • Not organized into Lines of Zahn. Just an amorphous mass of RBCs enmeshed in platelets and fibrin.
    • Appear 'red', hence termed 'Red or Stasis Thrombi'
    • Usually (90%) occurs in veins of lower extremities (See Deep Venous Thrombosis)
  • Postmortem Thrombi
    • Can develop after death
    • Are distinguished by lack of attachment to vessel wall (all others are usually firmly attached)
Fate of Thrombi
  • Propagate: Accumulate further fibrin/platelets. Arterial thrombi usually propagate against blood flow. Venous thrombi usually propagate with blood flow.
  • Embolization: Thrombus detaches from vessel wall and travels to other sites (See Thromboembolism)
  • Dissolution: Fibrinolytic mechanisms dissolve clot
  • Organization: Eventually thrombus can be 'organized' via fibrosis and potentially recanalized with new blood vessels.