Benefit of First Pass Complete Reperfusion in Thrombectomy is Mediated by Limited Infarct Growth.

Purpose Number of Clot Retrieval Attempts (CRA) to achieve complete reperfusion by mechanical thrombectomy impacts functional outcome in acute ischemic stroke (AIS). Complete reperfusion (expanded Treatment In Cerebral Infarction; eTICI=3) at First-Pass (FP), is associated with highest rates of favorable outcome compared to complete reperfusion by multiple CRA. This study aimed at investigating the relationship between FP complete reperfusion and Infarct Growth (IG). Methods Anterior AIS patients with baseline and 24h MR-Diffusion Weighted Imaging (DWI) were included from two prospective registries. IG was measured by voxel-based segmentation of initial and 24h-DWI lesions. IG and favorable 3-months modified Rankin Scale (mRS≤2) were compared between single and multiple CRA eTICI3, after matching for confounding factors. Mediation analysis tested the association between FP and 3-months mRS with IG as mediating variable. Results 200 patients were included with 118(28.9%) FP complete reperfusion. In case-control analysis, First-Pass population had lower IG than multiple CRA eTICI3 population (8.7ml[5.4-12.9] versus 15.2ml[11-22.6] respectively, p=0.03). Favorable outcome was higher in FP population compared to a matched multiple CRA population (70.9% versus 53.2% respectively, p=0.04). FP eTICI3 was independently associated with favorable outcome in multivariable regression analysis (OR=1.86 95%CI [1.01-4.39] P=0.04). Effect of complete reperfusion at first pass on functional outcome was explained by limited IG in mediation analysis (indirect effect: -0.32 [-0.47 to -0.09]). Conclusion Complete reperfusion at first pass is independently associated with significant decrease in IG compared to complete reperfusion by multiple attempts, explaining better functional outcome.