First-Pass Reperfusion by Mechanical Thrombectomy in Acute M1 Occlusion: The Size of Retriever Matters

Introduction: Single-pass complete reperfusion using stent retrievers has been shown to improve functional outcome in patients with large vessel occlusion strokes. The aim of this study was to investigate the optimal size of stent retrievers to achieve one-pass complete reperfusion by mechanical thrombectomy. Methods: The study evaluated the results of aspiration-assisted mechanical thrombectomy of acute isolated occlusion of the middle cerebral artery in the M1 segment with a novel 5 x 40-mm stent retriever compared to the usual 4 x 20-mm device. Reperfusion status was quantified using the Thrombolysis In Cerebral Infarction (TICI) scale. We hypothesized that thrombectomy of M1 occlusions with 5 x 40-mm stent retriever yields higher rates of complete first-pass reperfusion (FP) (TICI >= 2c after one pass) and successful or modified FP (mFP) (TICI >= 2b after one pass) than thrombectomy with 4 x 20. We included isolated M1 occlusions treated with pRESET 5 x 40 (phenox) as first-choice device for thrombectomy and compared with M1 occlusions treated with pRESET 4 x 20. We excluded patients with additional occlusions or tandem stenosis or who received an intracranial stent or angioplasty as a part of the endovascular treatment. Results: One hundred thirteen patients were included in the 4 x 20 group and 57 patients in the 5 x 40 group. The 5 x 40 group achieved higher FP compared to 4 x 20 group [61.4% (35 of 57 patients) vs. 40.7% (46 of 113), respectively; adjusted odds ratio (OR) and 95% confidence interval (95% CI) = 2.20 (1.08-4.48), p = 0.030] and a higher mFP [68.4%, 39 of 57 patients vs. 48.7%, 55 of 113; adjusted OR (95% CI) = 2.11 (1.04-4.28), p = 0.037]. Frequency of successful reperfusion (TICI >= 2b) was similar in both groups (100 vs. 97.3%), but frequency of complete reperfusion (TICI >= 2c) was higher in the 5 x 40 group [82.5 vs. 61.9%, adjusted OR (95% CI) = 2.47 (1.01-6.04), p = 0.047]. Number of passes to achieve reperfusion was lower in the 5 x 40 group than in the 4 x 20 group [1.6 +/- 1.1 vs. 2 +/- 1.4, p = 0.033; adjusted incidence rate ratio (95% CI) = 0.84 (0.69-1.03), p = 0.096]. Modified Rankin scale at 90 days was similar in 5 x 40 and 4 x 20 groups. Conclusions: The size of stent retriever matters in acute M1 occlusions treated with aspiration-assisted mechanical thrombectomy. A longer stent retriever with a larger nominal diameter achieves a higher complete and successful FP and higher successful reperfusion compared to a shorter stent retriever.