A245 Edema reduction as a key mediator of mechanical thrombectomy benefit in large core stroke

<h3>Introduction</h3> Recently, several trials observed improved functional outcomes for endovascular thrombectomy (EVT) in patients presenting with large ischemic lesions. However, the effect of recanalization on lesion pathophysiology in large strokes is not yet well understood. <h3>Aim of Study</h3> We hypothesized that EVT is linked to edema reduction as major pathophysiological link, independent of lesion size. <h3>Method</h3> The TENSION trial was a randomized, multicenter clinical trial enrolling patients with anterior circulation stroke and ASPECTS scores 3–5. Edema formation was calculated using the difference (∆NWU) of quantitative net water uptake (NWU) based on relative hypoattenuation in baseline and follow-up CT. Lesion extent in baseline and follow-up was assessed using ASPECTS. Mediation analyses were performed with EVT as independent variable and ∆NWU as mediator variable. <h3>Results</h3> For this pilot study, 92 patients were included. The median NWU and ASPECTS in follow-up CT were 26.8% (IQR: 1.9–34.7) and 2 (IQR: 1–3), respectively. Patients undergoing EVT showed significantly lower edema formation from baseline to follow-up (5.9% versus 12.8%, p&lt;0.001). In mediation analysis, 34% of the effect of EVT was mediated by edema reduction, while only 14% was mediated by changes on lesion extent. <h3>Conclusion</h3> EVT significantly modified edema formation from baseline to follow-up imaging independent of the lesion extent. Reduced ischemic water uptake into the ischemic lesion may represent an important link between improved functional outcome following EVT in large strokes. <h3>Conflict of Interest</h3> Yes Personal fees from Acandis, Research grant from DFG, Research grant from ASNR