Abstract Number ‐ 151: Impact of Stent‐Retriever Tip Design on Distal Embolization during Mechanical Thrombectomy
Authors: Li Jiahui , Tiberi Riccardo , Vargas Daniel , Bhogal Pervinder , Buhk Jan‐Hendrik , Behme Daniel , Tomasello Alejandro , Ribo Marc 
Published: April 2023

Introduction
Mechanical thrombectomy (MT) is a widely performed procedure for acute ischemic stroke (AIS) due to large vessel occlusion. Repeated number of passes, clot fragmentation, and distal embolization during MT lead to worse clinical outcomes. We aim to evaluate the impact of different stent‐retriever (SR) distal tip designs on distal emboli generation during MT.

Methods
Fragment‐prone clot analogs (diameter = 3.53±0.14mm; length = 6.74±0.61mm) were used to create proximal middle cerebral artery (MCA‐M1) occlusions in an in vitro neurovascular model featuring a complete circle of Willis. The anatomical replica was connected to a flow loop with circulating saline at physiological flow rate and temperature; 100‐µm filters were placed at the neurovascular outflow points of the model to collect generated distal emboli. After initial embolization, experiments were randomized into one of the three treatment arms based on SR tip design: open‐end (Open‐SR: Solitaire 6.0×40mm), closed‐end (Closed‐SR: Embotrap II 5.0×33mm), and filter‐end (Filter‐SR: NeVa NET 5.5×37mm). A balloon guide catheter was inflated at the internal carotid artery C1 level immediately after SR deployment, and the SR was pulled out under continuous proximal pump aspiration. A total of 90 cases were performed (30 cases/treatment arm). A single attempt was performed per case and after each pass, distal emboli collected in the outflow filters were analyzed by an image processing algorithm. Successful first pass recanalization (FPR) was confirmed if no residual clot was observed at the initial location or in a distal branch of the model. Primary study endpoints were: FPR rate (%FPR), the size of the largest embolus (largest‐E), the total emboli count (total‐E), the total count of emboli larger than 1mm (total>1mm‐E), and the total area of the filter covered by emboli (area‐E).

Results
FPR was achieved in 57.8% of cases (52/90): Filter‐SR achieved a non‐significantly higher %FPR (70%) than closed‐SR (50%) and open‐SR (53.3%) (p = 0.244). In comparison to open‐ and closed‐SR, filter‐SR significantly reduced the largest‐E (open‐SR = 1.66±0.68mm vs. closed‐SR = 1.77±0.90mm vs. filter‐SR = 1.22±0.77mm; p = 0.013) as well as the total>1mm‐E (open‐SR = 2.27±2.33 vs. closed‐SR = 3.97±5.68 vs. filter‐SR = 0.93±1.28; p = 0.002), and the area‐E (open‐SR = 18.22±14.47mm2 vs. closed‐SR = 23.98±22.39mm2 vs. filter‐SR = 10.14±8.81mm2; p = 0.013). The differences between distal tip designs were not clearly evidenced in the total‐E (open‐SR = 22.7±10.75 vs. closed‐SR = 23.13±13.16 vs. filter‐SR = 20.63±12.77; p = 0.464). No significant differences were found between open‐ and closed‐SR (p>0.05 in all metrics).

Conclusions
When facing fragment‐prone clots with low SR engagement, the filter‐SR significantly reduces the number of large clot fragments (>1mm), the size of the largest embolus, and the overall surface area of clot fragments that embolize distally during an MT procedure.