Comparison of 4 mm-sized and 3 mm-sized Stent Retrievers in Mechanical Thrombectomy for M2 Occlusion

Introduction: A stent retriever (SR) is widely used in mechanical thrombectomy (MT) for M2 segment occlusion. However, the suitable size of SR in M2 occlusion remains unclear. Therefore, we aimed to compare 4 mm-sized SR with 3 mm-sized SR in M2 occlusion. Methods: Patients who underwent MT with SR for M2 occlusion were dichotomized into 4×20 mm SR and 3×20 mm SR groups. Then, 1:1 propensity score matching was performed. The M2 segment was divided into proximal and distal segments according to the occlusion site. Subgroup analysis was then performed for each cohort. Results: A total of 111 patients were enrolled, with 4×20 mm SR and 3×20 mm SR applied in 72 (64.9%) and 39 (35.1%) cases, respectively. In propensity score matching, mean number of stent passages for reperfusion was significantly lower in the 4×20 mm SR group than in the 3×20 mm SR group (1.5 ± 0.8 vs. 2.1 ± 1.1; p = 0.004). First-pass reperfusion (FPR) was more highly achieved in the 4×20 mm SR group than in the 3×20 mm SR group (52.6% vs. 42.1%; p = 0.007). In both proximal and distal occlusion cohorts, the 4 mm SR group showed lower mean number of SR passage (p = 0.004 and p = 0.003, respectively) and higher FPR rate than the 3 mm SR group (p = 0.003 and p = 0.007, respectively). Conclusion: In MT for M2 occlusion, 4×20 mm SR enables an effective procedure with lesser SR passage for reperfusion and a higher rate of FPR than 3×20 mm SR.