Immunothrombotic Dysregulation in Pediatric Patients Receiving Veno-arterial ECMO After Cardiac Surgery: Insights From Platelet Activation and T Cell Immune Profiling.

Background: Numerous studies have demonstrated that both cardiopulmonary bypass (CPB) and extracorporeal membrane oxygenation (ECMO) are often associated with adverse outcomes or immune dysregulation when platelet counts decline during support. Moreover, the severity of thrombocytopenia generally correlates with a worse clinical prognosis. However, the underlying mechanisms remain incompletely understood. Previous research has attributed this phenomenon to hemodynamic alterations during CPB and ECMO, as well as anticoagulant-induced abnormal platelet activation. Based on our clinical observations, we question the completeness of this explanation and propose an alternative hypothesis: sustained platelet activation during ECMO serves as an initiating factor that contributes to both progressive thrombocytopenia and immune dysfunction throughout the support period. Methods: We investigated platelet activation status, degranulation capacity, and T cell subset dynamics in patients receiving ECMO support. Flow cytometry was used to assess platelet surface markers, reticulated platelet proportions, and T cell subset distributions. Results: We demonstrate that platelets exhibit excessive activation during ECMO, accompanied by a gradual decline in their degranulation capacity. Notably, even with an increased proportion of newly formed platelets, this functional impairment persists. Furthermore, we observed significant alterations in Helper T cell Type 1 (Th1) and CD8+ T cell populations during ECMO support. Conclusions: Our findings suggest that aberrantly activated platelets during ECMO amplify the specific recognition of platelet antigens by CD8+ T cells via modulating the differentiation bias of CD4+ T cells, particularly Th1 cells, ultimately leading to platelet depletion. These results suggest that early interventions targeting abnormal platelet activation may represent a potentially effective therapeutic strategy to mitigate ECMO-associated thrombocytopenia.