Abstract WP160: First-Pass Effect Modification In Proximal Vs Distal M1 Occlusion Thrombectomy

Abstract

Modified first pass effect (mFPE) of TICI 2B or greater is an independent predictor of clinical outcome in patients who undergo mechanical thrombectomy (MT). Location of the occlusion in the M1 segment may affect the mFPE and may influence clinical outcomes. A comparison of mFPE between occlusions of the proximal and distal (sparing lenticulostriate branches) M1 segments of the MCA has yet to be performed. We aim to examine the interaction between first pass effect and clinical outcomes in proximal versus distal M1 occlusions. We performed retrospective analysis of patients who underwent MT between 2014 and 2020. Patients were included if they were treated for M1 occlusion within 24 hours from last seen normal, and achieved successful recanalization (TICI2b or greater). Patients were excluded if they were not successfully recanalized, or if they had other intracranial or multifocal occlusions. A total of 264 patients were included in this analysis. Ninety two patients had proximal M1 occlusions and 172 had distal M1 occlusions. Patients with proximal M1 occlusions had higher NIHSS (median 18 vs. 16, p=0.003), lower ASPECTS (mean 8.5 vs 9, p=0.02), and were less likely to be females (44.6% vs. 62.8%, p=0.006). Modified first pass effect was achieved in 45.3% of distal M1 occlusions compared to 31.9% of proximal (p=0.047). Excellent clinical outcome, defined as mRS of 0-1 at 90 days was higher in distal occlusion group (38.8% vs. 24.7%, p=0.03). Additionally, the proximal occlusion group was more likely to experience any grade of hemorrhagic transformation (HT) (37.4 vs. 23.3, p=0.02). Other baseline characteristics and time metrics did not differ between the two groups. In a multivariate analysis of predictors of excellent outcome in the overall cohort, ASPECTS (OR=1.39, p = 0.026) and proximal occlusion site (OR=0.485, p=0.037) were the only two independent predictors. Therefore, mFPE was not a predictor of excellent outcome when adjusted for exact location of occlusion.