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The Thromboembolism Heparinization and AntithrombiN Observational Study (THANOS-1).
Christiana K Prucnal1,2,3,4, Grace Wang1, Weixing Huang5
1Center for Vascular Emergencies, Department of Emergency Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts, USA.
Research and Practice in Thrombosis and Haemostasis
|February 27, 2026
Summary
Acquired antithrombin (AT) deficiency is common in acute pulmonary embolism (PE) patients, affecting over a quarter. Low AT levels correlate with adverse outcomes and longer hospital stays, but the link to anticoagulation effectiveness requires further study.
Area of Science:
- Cardiology
- Hematology
- Critical Care Medicine
Background:
- Acute pulmonary embolism (PE) impacts hemodynamics and coagulation.
- PE may induce an acquired antithrombin (AT) deficiency, potentially limiting heparin efficacy.
- The prevalence and clinical impact of acquired AT deficiency post-PE are not well-established.
Purpose of the Study:
- To determine the proportion of PE patients with acquired AT deficiency (defined as <80% functional activity).
- To investigate associations between acquired AT deficiency and clinical factors or outcomes.
- Secondary analyses explored AT activity thresholds of <90%, <100%, and <110%.
Main Methods:
- Prospective, observational study design.
- Included patients diagnosed with acute PE without heparin contraindications.
- Measured AT activity within 24 hours of PE diagnosis; outcomes extracted from medical records.
Main Results:
- 200 patients analyzed (60% male, mean age 62).
- 27% had <80% AT activity, 56% <90%, and 80% <100%.
- Low AT activity (<80%) linked to longer hospital stay, ICU admission, and adverse outcomes, but not subtherapeutic anticoagulation.
Conclusions:
- Acquired AT deficiency is a frequent complication of acute PE, seen in at least 27% of patients.
- Low AT levels are associated with adverse clinical outcomes and increased hospital resource utilization.
- The relationship between low AT levels and subtherapeutic anticoagulation requires further investigation.
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