Correcting High Maximum Amplitude (MA) on Thromboelastography (TEG)
For patients with high Maximum Amplitude (MA) on TEG indicating hypercoagulability, therapeutic anticoagulation with low molecular weight heparin (LMWH) or unfractionated heparin (UFH) is recommended, with LMWH preferred in pregnant patients due to its better safety profile. 1
Understanding High MA on TEG
- Maximum Amplitude (MA) represents the maximum strength of the clot and primarily reflects platelet function and fibrinogen concentration 1
- Increased MA (>70mm) indicates a hypercoagulable state, which increases thrombotic risk 1
- High MA is associated with increased risk of venous thromboembolism (VTE), with studies showing the rate of deep vein thrombosis doubles in trauma patients with hypercoagulable TEG 2
Treatment Algorithm for High MA
First-Line Therapy
- For severe hypercoagulability or high thrombotic risk, initiate therapeutic anticoagulation with LMWH or UFH 1
- LMWH is preferred over UFH in pregnant patients due to better safety profile and more predictable anticoagulant effect 3
- In a study comparing anticoagulants, 40mg enoxaparin (LMWH) showed greater anticoagulant effect than 7500 IU UFH, with 73% of patients becoming hypocoagulable with LMWH versus only 47% with UFH 3
Monitoring Response
- Repeat TEG 15-30 minutes after intervention to assess response 1
- Target MA normalization (typically <70 mm) 1
- The anticoagulant effect on TEG is defined as a difference >25% between plain and heparinase R time samples 3
Special Considerations
Pregnancy
- Pregnancy naturally induces a hypercoagulable state with increased MA values 3
- Women with mild preeclampsia are more hypercoagulable compared to healthy pregnant women 3
- As preeclampsia severity worsens, blood coagulability decreases, particularly in women with platelet counts <100,000/mm³ 3
Obesity
- Studies show a trend of increasing hypercoagulability with increasing body mass index (BMI) 3
- In bariatric surgery patients, 23.3% showed hypercoagulability prior to surgery with G ≥11 dynes/cm² or MA ≥68 mm 4
COVID-19
- COVID-19 patients often demonstrate hypercoagulability on TEG with increased MA values 5
- However, TEG parameters alone may not be sufficient to discriminate for thrombotic events in COVID-19 patients 6
Pitfalls to Avoid
- Anemia can paradoxically show hypercoagulable TEG results due to decreased blood viscosity, potentially exaggerating the MA value 1
- TEG shows high coefficients of variance (7.1-39.9%), so results should be interpreted with caution and in clinical context 1
- Results vary between devices and are not interchangeable between TEG and ROTEM systems 1
- Standard TEG is insensitive to antiplatelet agents and cannot reliably detect platelet dysfunction 1
Risk Assessment and Prevention
- In trauma patients, hypercoagulable TEG remains associated with DVT even after adjustment for relevant covariates, with an odds ratio of 2.41 2
- Consider prophylactic anticoagulation in patients with high MA who have additional risk factors for thrombosis 1
- For transfusion-dependent thalassemia patients, the risk of developing a hypercoagulable state appears higher when the volume of RBCs transfused is less than 154 mL/kg/year 7