Introduction

Thromboelastography (TEG) is a point-of-care test that assesses the viscoelastic properties of blood clotting. It was developed by Dr. Hellmut Hartert in 1948. Unlike conventional coagulation tests (PT, aPTT, INR), TEG evaluates clot formation from fibrin generation to clot lysis, providing a real-time assessment of coagulation.

Principle of TEG

  • A small amount of whole blood is placed in a heated cup and rotated around a pin suspended in it.
  • As the clot forms, it transmits torque to the pin, generating a graphical representation of clot dynamics.
  • The degree and speed of clot formation determine the tracing characteristics.

Components of TEG Machine

  • Sample Cup: Holds the blood sample.
  • Pin and Torsion Wire: Detects clot formation and transmits data.
  • Heating Element: Maintains the sample at body temperature (37°C).
  • Computer Interface: Converts mechanical signals into graphical representation.

TEG Parameters and Their Interpretation

TEG Graph Interpretation

  • Normal TEG: Balanced coagulation with normal R, K, α-angle, and MA.
  • Hypercoagulable State: Short R time, increased α-angle, and high MA (e.g., pregnancy, malignancy).
  • Hypocoagulable State: Prolonged R and K times, decreased α-angle and MA (e.g., factor deficiency, liver disease).
  • Primary Hyperfibrinolysis: Normal clot formation but increased LY30 (e.g., trauma-induced coagulopathy).

Clinical Applications of TEG

  • Cardiac Surgery: Guides transfusion therapy and anticoagulation management.
  • Trauma and Massive Transfusion: Helps in goal-directed blood component therapy.
  • Liver Transplantation: Evaluates coagulopathy and fibrinolysis.
  • Obstetric Hemorrhage: Identifies hyperfibrinolysis and guides antifibrinolytic therapy.
  • Sepsis and DIC: Detects early coagulopathy and fibrinolytic shutdown.

Advantages of TEG Over Conventional Coagulation Tests

  • Real-time assessment of clot formation and breakdown.
  • Point-of-care availability.
  • Assesses both cellular (platelet) and plasma (coagulation factor) components.
  • Guides goal-directed transfusion therapy.

Limitations of TEG

  • Operator-dependent interpretation.
  • Not widely available in all settings.
  • Requires standardization for optimal use.
  • Affected by hematocrit variations.

TEG vs ROTEM (Rotational Thromboelastometry)

  • ROTEM is a modification of TEG with automated data acquisition.
  • ROTEM uses different activators to differentiate clotting pathways.
  • TEG is more commonly used in the USA, whereas ROTEM is preferred in Europe.

Conclusion

Thromboelastography (TEG) is an invaluable tool for assessing coagulation in real time, providing insights into clot formation, strength, and lysis. It aids in individualized patient management, especially in perioperative and critical care settings. Understanding TEG parameters and their interpretation is crucial for optimizing patient outcomes in coagulopathy management.