Aims 
Intracoronary thrombus formation is a main cause of acute myocardial infarction in patients with coronary artery disease (CAD) triggered by platelet activation and monocyte differentiation. However, there are no valid data on the differential impact of pre-treatment strategies with antiplatelet agents on thrombus formation. In this study we investigate the impact of periinterventional application of the P2Y12-inhibitors clopidogrel and prasugrel on thrombus architecture and its cell content, highlighting significant changes associated with the antiplatelet pretreatment. 
Methods & Results 
We prospectively analyzed the influence of antiplatelet therapy on thrombus formation in 104 consecutive patients with acute of acute (<24 h) or recent (24 to72 h) ST-segment elevation myocardial infarction (STEMI) undergoing immediate percutaneous intervention and thrombus aspiration by immunohistochemical and histological staining along with RNA-sequencing employing Nanostring analysis. N=52 patients were treated with clopidogrel loading (600 mg) and n=52 patients received prasugrel loading (60 mg) prior PCI.

Interestingly, intracoronary thrombus architecture was significantly altered between patients pretreated with clopidogrel when compared to prasugrel. Fibrin content of thrombi was significantly increased after pretreatment with clopidogrel. Furthermore, levels of myeloperoxidase (MPO) positive cells in intracoronary thrombi were significantly increased in patients with clopidogrel pretreatment indicating an association of antiplatelet pretreatment and inflammatory responses during thrombus formation. In addition, thrombus composition and cell differentiation was dependent on duration of symptom onset in patients with STEMI. To strengthen the finding of altered thromboinflammatory signaling in patients with STEMI, we performed RNA expression analysis. Most strikingly, we observed significant differences among both pretreatment groups regarding altered RNA expression and signalling pathways of thromboinflammatory processes within the thrombotic material, which were independently associated with antiplatelet strategies and not significantly impacted by other possible confounding factors (A). Highlighting significantly altered gene expression (B), a distinct separation of treatment subgroups is displayed and implementing a critical influence of antiplatelet loading strategy on thromboinflammatory cascades in  patients with STEMI (C). To elucidate the impact of antiplatelet loading treatment on RNA expression levels we performed enrichment analysis highlighting altered thromboinflammatory pathways (D) and referring subnetworks in patients with clopidogrel and prasugrel treatment, respectively (E).

Conclusion & Translational Perspective
In this study we reveal that thrombus architecture in patients with acute myocardial infarction is critically associated with antiplatelet pretreatment. Fibrosis and levels of thromboinflammatory markers in intracoronary thrombi are significantly higher after application of clopidogrel compared to prasugrel. RNA expression further indicated critically altered signaling in patients with clopidogrel treatment compared to prasugrel-treated patients. Results of this study may contribute to the understanding of antiplatelet pretreatment remodelling thrombus architecture and thus lower the risk of adverse events.