Introduction Successful recanalization by mechanical thrombectomy improves functional outcome of patients with ischemic stroke. However, infarct volume at 24h only partly explains long-term functional outcome [1-4].

Aim of Study A better understanding of the interplay between thrombectomy-related infarct volume reduction and post-acute rehabilitation measures might allow optimized medical management. We hypothesize that the proportion of the treatment effect explained by reduction of infarct volume is higher at earlier time points and decreases at 90-day follow-up due to improvements related to post-acute medical management.

Methods All patients enrolled in the German Stroke Registry(05/2015-12/2019) in our institution were screened. Mediation analysis was conducted to quantify the effect of successful recanalization (mTICI≥2b) on improvement in functional outcome (mRS≤2) explained by infarct volume reduction at discharge and at day 90.

Results 429 patients were included (table 1). At discharge, successful recanalization was associated with a 20 percentage points (pp) [95%CI:13pp-27pp] higher probability of good functional outcome, 71%[49%-98%] of the effect was explained by infarct volume reduction. At day 90, successful recanalization increased probability of good outcome by 23pp[16pp-29pp], 56% of the effect was explained by infarct volume reduction (figure 1)

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Abstract P019 Figure 1

Mediation model structure and results

Conclusion At discharge 71% of the treatment effect was explained by infarct volume reduction, at day 90, the proportion explained was 56%, suggesting significant influence of factors that manifest between discharge and day 90, such as rehabilitation measures and late adverse events. Results reflect the importance of post-acute management until day 90, contributing 15% to the observed improvement in functional outcomes.

Disclosure of Interest yes Helge Kniep and Fabian Flottmann are consultants for Eppdata GmbH. Helge Kniep is shareholder of Eppdata GmbH. Götz Thomalla received fees as consultant from Acandis, Boehringer Ingelheim, Bayer, and Portola, and fees as lecturer from Acandis, Alexion, Amarin, Bayer, Boehringer-Ingelheim, BMS/Pfizer, Daiichii Sankyo and Portola. He serves in the board of the TEA Stroke Study and of ESO. Jens Fiehler is consultant for Cerenovus, Medtronic, Microvention, Penumbra, Phenox, Roche and Tonbridge. He serves in the advisory board of Stryker and Phenox. He is stock holder of Tegus Medical, Eppdata and Vastrax. He serves as Associate Editor at JNIS.