Predictors of functional outcome after thrombectomy for M2 occlusions: a large scale experience from clinical practice

Mechanical thrombectomy (MT) for acute ischemic stroke with medium vessel occlusions is still a matter of debate. We sought to identify factors associated with clinical outcome after MT for M2-occlusions based on data from the German Stroke Registry-Endovascular Treatment (GSR-ET). All patients prospectively enrolled in the GSR-ET from 05/2015 to 12/2021 were analyzed (NCT03356392). Inclusion criteria were primary M2-occlusions and availability of relevant clinical data. Factors associated with excellent/good outcome (modified Rankin scale mRS 0-1/0-2), poor outcome/death (mRS 5-6) and mRS-increase pre-stroke to day 90 were determined in multivariable logistic regression. 1348 patients were included. 1128(84%) had successful recanalization, 595(44%) achieved good outcome, 402 (30%) had poor outcome. Successful recanalization (odds ratio [OR] 4.27 [95% confidence interval 3.12-5.91], p<0.001), higher Alberta stroke program early CT score (OR 1.25 [1.18-1.32], p<0.001) and i.v. thrombolysis (OR 1.28 [1.07-1.54], p<0.01) increased probability of good outcome, while age (OR 0.95 [0.94-0.95], p<0.001), higher pre-stroke-mRS (OR 0.36 [0.31-0.40], p<0.001), higher baseline NIHSS (OR 0.89 [0.88-0.91], p<0.001), diabetes (OR 0.52 [0.42-0.64], p<0.001), higher number of passes (OR 0.75 [0.70-0.80], p<0.001) and intracranial hemorrhage (OR 0.26 [0.14-0.46], p<0.001) decreased the probability of good outcome. Additional predictors of mRS-increase pre-stroke to 90d were dissections, perforations (OR 1.59 [1.11-2.29], p<0.05) and clot migration, embolization (OR 1.67 [1.21-2.30], p<0.01). Corresponding to large-vessel-occlusions, younger age, low pre-stroke-mRS, low severity of acute clinical disability, i.v. thrombolysis and successful recanalization were associated with good outcome while diabetes and higher number of passes decreased probability of good outcome after MT in M2 occlusions. Treatment related complications increased probability of mRS increase pre-stroke to 90d.