High Maximum Amplitude (MA) on TEG Indicates Hypercoagulability
A high MA on thromboelastography indicates a hypercoagulable state, reflecting increased clot strength primarily from elevated fibrinogen levels and enhanced platelet-fibrinogen interactions, which correlates with increased thrombotic risk. 1
Understanding Maximum Amplitude
MA represents the maximum strength of the clot, measured as the widest point on the TEG tracing, and reflects the combined contribution of fibrinogen and platelet function to clot firmness 1, 2
Normal MA values typically range from 50-70 mm, with values above this range indicating hypercoagulability 1
Increased MA directly correlates with enhanced thrombotic risk, as demonstrated in multiple clinical contexts including trauma, stroke, and malignancy 1, 3, 4
Clinical Significance and Thrombotic Risk
Elevated MA is an independent predictor of thromboembolic events across multiple patient populations 1
In trauma patients, admission MA >65 mm carries an odds ratio of 3.5 for developing pulmonary embolism, increasing to 5.8 for MA >72 mm 4
In ischemic stroke patients, higher MA levels independently predict unfavorable one-year functional outcomes (OR = 1.192), along with increased risk of recurrent ischemic events 3
Among patients with musculoskeletal tumors, 60% demonstrate preoperative hypercoagulability on TEG, with 16% of these patients developing symptomatic postoperative deep vein thrombosis compared to 0% in those with normal TEG profiles 5
Pathophysiology of Elevated MA
High MA primarily reflects elevated fibrinogen levels, with strong correlation between fibrinogen concentration and MA values (R=0.431) 6
Fibrinogen levels can predict clot strength (G) ≥11 dynes/cm² with moderate accuracy (AUC=0.680) 6
Enhanced platelet aggregation and platelet-fibrinogen interactions contribute to increased clot strength, though standard TEG is relatively insensitive to antiplatelet agents 2, 7
Special Clinical Contexts
Pregnancy and Obstetrics
Pregnancy naturally increases MA values due to physiologic hypercoagulability, with progressive increases throughout gestation 8, 1
Women with mild preeclampsia demonstrate greater hypercoagulability than healthy pregnant women, though paradoxically, as preeclampsia severity worsens and platelet counts fall below 100,000/mm³, coagulability decreases 1
TEG measurements show increased coagulability in preeclampsia, with MA being superior to standard laboratory tests in evaluating this condition 8
Obesity and Bariatric Surgery
In bariatric surgery patients, 23.3% demonstrate preoperative hypercoagulability (G ≥11 dynes/cm²) and 28.3% have MA ≥68 mm at baseline 6
Increasing BMI shows a trend toward greater hypercoagulability, though the hypercoagulable effect of term pregnancy appears greater in magnitude than obesity alone 1
Malignancy
- Patients with musculoskeletal tumors show high rates of hypercoagulability, with older age, female sex, and soft tissue disease (versus bony disease) being independent risk factors 5
Management Approach
For severe hypercoagulability with high thrombotic risk, initiate therapeutic anticoagulation with low molecular weight heparin (LMWH), particularly in pregnant patients where LMWH is preferred over unfractionated heparin 1
In pregnancy, 40 mg enoxaparin demonstrates greater anticoagulant effect than 7500 IU unfractionated heparin, with 73% of patients becoming hypocoagulable versus only 47% with UFH 1
The anticoagulant effect on TEG is defined as a difference >25% between plain and heparinase R time samples 1
Repeat TEG 15-30 minutes after any anticoagulation intervention to assess response 1
Critical Pitfalls to Avoid
Anemia can paradoxically show hypercoagulable TEG results (including elevated MA) due to decreased blood viscosity, potentially masking true coagulopathy or exaggerating hypercoagulability 1, 2
TEG shows high coefficients of variance (7.1-39.9% for TEG parameters), requiring interpretation in clinical context rather than relying on isolated values 1, 2
Results are not interchangeable between TEG and ROTEM devices—CFF MA values differ significantly from FIBTEM MCF values even at identical fibrinogen concentrations 1
Standard TEG is insensitive to antiplatelet agents and cannot reliably detect platelet dysfunction, limiting its utility in assessing antiplatelet therapy effectiveness 2, 7
TEG is performed at 37°C and cannot assess effects of hypothermia on coagulation 2
Risk Stratification Based on MA Values
MA >68 mm defines hypercoagulability in most clinical contexts, though specific thresholds may vary by clinical scenario 6
MA >65 mm in trauma patients warrants heightened surveillance for venous thromboembolism 4
Consider more aggressive thromboprophylaxis regimens in patients with markedly elevated MA, particularly those with additional risk factors such as malignancy, advanced age, or immobility 5