Identification of Coagulation Phenotypes Using Viscoelastic and Conventional Assays During Veno‐Venous Extracorporeal Membrane Oxygenation: A Hierarchical Clustering Analysis

ABSTRACT Background Veno‐venous extracorporeal membrane oxygenation (V‐V ECMO) is essential for managing severe respiratory failure; however, hemorrhagic and thrombotic complications remain major challenges. Conventional activated partial thromboplastin time (APTT) monitoring may inadequately reflect the complex coagulation changes during ECMO. Although viscoelastic hemostatic assays (VHAs) provide a comprehensive assessment, discrepancy patterns between VHAs and conventional tests in V‐V ECMO patients remain unclear. Objectives This study aimed to identify distinct coagulation phenotypes in patients receiving V‐V ECMO using hierarchical clustering of VHA and conventional coagulation parameters. Methods This retrospective observational study was conducted at a tertiary university hospital in Japan. Patients receiving V‐V ECMO between November 2020 and June 2023 who underwent VHA and conventional coagulation testing were included. Coagulation profiles were clustered using hierarchical analysis of five variables. Cluster validity was assessed, and results were visualized using principal component analysis and generalized additive models. Results A total of 19 patients and 110 VHA measurements were analyzed. Three distinct coagulation phenotypes were identified. Cluster 1 demonstrated concordant prolongation of APTT and citrated kaolin reaction time (CK‐R). Clusters 2 and 3 exhibited disproportionately prolonged CK‐R relative to APTT, with Cluster 3 further characterized by elevated fibrinogen and platelet counts. Anticoagulant use, laboratory markers, and clinical outcomes, including thrombotic and bleeding events, were evaluated. Complication rates did not differ significantly among clusters. Conclusions Hierarchical clustering identified three distinct coagulation profiles among V‐V ECMO patients, highlighting the heterogeneity of ECMO‐related coagulopathy. Thromboelastography‐derived CK‐R may complement APTT monitoring to inform more tailored anticoagulation strategies in this population.