Abstract WP5: Reperfusion Reduces Brain Edema in Patients With Acute Ischemic Stroke. A MR CLEAN Substudy

Introduction: The main objective of this study was to elucidate the relation between reperfusion and brain edema. The secondary objective was to evaluate if brain edema partially mediated worse outcome in patients without reperfusion, or in patients with delayed reperfusion or a lower ASPECTS. Methods: MR CLEAN was a prospective, randomized, multicenter clinical trial of endovascular treatment (EVT) compared to conventional care. In this exploratory post hoc study, 462 of 500 patients were included. Brain edema was assessed by midline shift (MLS) measured on follow-up CT scans. Reperfusion status was assessed by the modified thrombolysis in cerebral infarction (mTICI) score in the EVT arm. The modified Arterial Occlusive Lesion (mAOL) score was used to evaluate the recanalization status in both arms. The associations between MLS and modified Rankin Scale (mRS), and MLS with reperfusion or recanalization were performed in univariable and multivariable analyses. Mediation analyses were performed to determine whether MLS was partially responsible for worse functional outcome in the groups without reperfusion or recanalization, and in the groups with delayed reperfusion or lower ASPECTS. Results: Reperfusion and recanalization were associated with reduced likelihood of having MLS (acOR 0.26, 95%CI 0.13-0.51, p < 0.001; acOR 0.38, 95%CI 0.24-0.60, p < 0.001 respectively). Accordingly, the presence of MLS was associated with an increased risk of worse 90-day outcome (acOR 3.89, CI 2.71-5.61, p < 0.001). In mediation analysis, MLS was partially responsible for worse mRS scores in patients without reperfusion or recanalization, and in those with delayed reperfusion or lower ASPECTS (MLS changed the logistic regression coefficients by 30.3%, 12.6%, 33.3%, and 64.2%, respectively). Conclusion: Successful reperfusion or recanalization reduces brain edema, reflected by MLS. The presence of MLS mediated part of the worse functional outcomes in patients without reperfusion or in those patients with delayed reperfusion or a lower ASPECTS. This study confirms a pleiotropic benefit of reperfusion that extends beyond the concept of rescuing ischemic brain tissue at risk for infarction.