Thrombelastogram (TEG)

Thrombelastogram (TEG)

David Ray Velez, MD

Table of Contents

Testing
Result Interpretation
Platelet Mapping

Testing

Basics

  • Measures the Viscoelastic Properties of Clot Formation in Real Time
  • Procedure:
    • A Small Cup of Blood is Activated and\ Rotates Around a Pin
    • A Clot Forms Around the Pin & Parameters are Measured
  • *Does Not Reliably Detect the Effects of Commonly Use Anticoagulants
  • Increasingly Being Used in Trauma and Critical Care
    • Conventional Tests Take a Long Time (Over 80 Minutes) and are Often Inaccurate by The Time They Result Due to Transfusions and Physiologic Changes
    • Used to Guide Massive Transfusion and Identify Trauma Induced Coagulopathy
    • May Decrease Transfusion Requirements (Controversial Area of Active Study)
    • *See Hemorrhagic Shock & Trauma Resuscitation

Commercial Types

  • Thrombelastogram (TEG)
    • *Not “Thromboelastogram” – Common Misspelling
  • Rotational Thromboelastography (ROTEM)
    • Similar but Different Nomenclature of Results

Modifications

  • Citrated Kaolin-Activated TEG (CK)
    • The “Standard” TEG Using Kaolin (A Type of Clay) to Activate Clot Formation
  • Citrated RapidTEG (CRT)
    • Uses Kaolin and Tissue Factor to Accelerate the Reaction
  • Citrated Functional Fibrinogen (CFF)
    • Added Cytochalasin D – Inhibits GP IIb/IIIa Platelet Activity
    • By Eliminating the Effect of Platelets, the New Maximum Amplitude Only Represents the Effects Fibrinogen
    • Used to Differentiate Deficiencies in Fibrinogen vs Platelets Deficiencies
  • Heparinase (CKH/HKH)
    • Types:
      • Citrated-Kaolin with Heparinase (CKH)
      • Heparinized-Kaolin with Heparinase (HKH)
    • Added Heparinase (Enzyme to Neutralize Heparin)
    • Used to Evaluate the Inhibitory Effects of Heparin (CK/CRT are Low but the CKH/HKH is Normal)
  • Platelet Mapping
    • Added Adenosine Diphosphate (ADP) and Arachidonic Acid
    • Measures Inhibitory Effects of Antiplatelet Agents (Aspirin/Clopidogrel)

Thrombelastogram (TEG) Mechanics 1

TEG Results

TEG Platelet Mapping

Result Interpretation

Reaction Time (R Time)/Activated Clotting Time (ACT)

  • Measures: Time to Initiate Clot Formation
  • Requires Coagulation Factors to Initiate Clot Formation
  • Normal:
    • Normal TEG: 5-10 Minutes
    • RapidTEG: 50-70 Seconds
  • Prolonged Time Indicates Coagulation Factor Deficiency
    • Treatment: FFP

K Time

  • Measures: Time to Reach a Fixed Strength
  • Requires Fibrinogen to Promote Rapid Platelet Cross-Linking
  • Normal: 1-3 Minutes
  • Prolonged Time Indicates Fibrinogen Deficiency
    • Treatment: Cryoprecipitate

α Angle

  • Measures: Speed of Growth
  • Requires Fibrinogen to Promote Rapid Platelet Cross-Linking
  • Normal: 53-72 Degrees
  • Low Angle Indicates Fibrinogen Deficiency
    • Treatment: Cryoprecipitate

Maximum Amplitude (MA)

  • Measures: Highest Vertical Amplitude
  • Requires Abundant Platelet Supply for a Maximum Size
    • May Also Be Affected by Fibrinogen to a Lesser Degree
  • Normal: 50-70 mm
  • Low CRT-MA Indicates a Platelets Deficiency
    • Treatment: Platelets
    • May Also Consider DDAVP or Cryoprecipitate
  • Low CFF-MA Indicates a Fibrinogen Deficiency
    • By Eliminating the Effect of Platelets, the New Maximum Amplitude Only Represents the Effects Fibrinogen
    • Treatment: Cryoprecipitate

Lysis at 30 Minutes (LY30)

  • Measures: Percentage of Clot Amplitude Reduction 30 Minutes After the Maximum
  • Normal: 0-3%
  • High Lysis Indicates Excessive Fibrinolysis
    • Treatment: TXA

Platelet Mapping

Clinical Use

  • Platelet Mapping is Used to Specifically Evaluate the Function of Platelets
  • The Exact Clinical Use and Management of Abnormal Results is Poorly Defined

Parameters

  • HKH (Heparinized-Kaolin with Heparinase)
    • Represents a Standard TEG Using Kaolin to Activate Clot Formation
    • Heparinase is Added to Eliminate the Effects of Heparin
    • Represents the Full Effects of Platelets and Fibrinogen
    • May Report CK (Citrated Kaolin-Activated TEG) Instead if Heparinase is Not Added
  • ActF (Activation of Fibrinogen Only)
    • Factor XIIIa is Added to Activate Fibrinogen
    • Only Represents the Effects of Fibrinogen, Not Platelets
  • AA (Arachidonic Acid)
    • Fibrinogen is Activated by Factor XIIIa and Platelets are Activated Through the Arachidonic Acid Receptor (Site of Aspirin Effects)
    • Represents the Effects of Aspirin on Platelet Binding
  • ADP (Adenosine Diphosphate)
    • Fibrinogen is Activated by Factor XIIIa and Platelets are Activated Through the Adenosine Diphosphate Receptor (Site of P2Y12 Inhibitor Effects)
    • Represents the Effects of P2Y12 Inhibitors (Clopidogrel) on Platelet Binding

References

  1. Hartmann J, Murphy M, Dias JD. Viscoelastic Hemostatic Assays: Moving from the Laboratory to the Site of Care-A Review of Established and Emerging Technologies. Diagnostics (Basel). 2020 Feb 21;10(2):118. (License: CC BY-4.0)