Impact of Clot Shape on Successful M1 Endovascular Reperfusion

Abstract

Objectives: The susceptibility-vessel-sign (SVS) allows thrombus visualization, length estimation and composition, and it may impact reperfusion during mechanical thrombectomy (MT). SVS can also describe thrombus shape in the occluded artery: in the straight M1-segment (S-shaped), or in an angulated/traversing a bifurcation segment (A-shaped). We determined whether SVS clot shape influenced reperfusion and outcomes after MT for proximal middle-cerebral-artery (M1) occlusions. Methods: Between May 2015 and March 2018, consecutive patients who underwent MT at one comprehensive stroke center and who had a baseline MRI with a T2^* sequence were included. Clinical, procedural and radiographic data, including clot shape on SVS [angulated/bifurcation (A-SVS) vs. straight (S-SVS)] and length were assessed. Primary outcome was successful reperfusion (TICI 2b-3). Secondary outcome were MT complication rates, MT reperfusion time, and clinical outcome at 90-days. Predictors of outcome were assessed with univariate and multivariate analyses. Results: A total of 62 patients were included. 56% (35/62) had an A-SVS. Clots were significantly longer in the A-SVS group (19 mm vs. 8 mm p = 0.0002). Groups were otherwise well-matched with regard to baseline characteristics. There was a significantly lower rate of successful reperfusion in the A-SVS cohort (83%) compared to the S-SVS cohort (96%) in multivariable analysis [OR 0.04 (95% CI, 0.002-0.58), p = 0.02]. There was no significant difference in long term clinical outcome between groups. Conclusion: Clot shape as determined on T2^* imaging, in patients presenting with M1 occlusion appears to be a predictor of successful reperfusion after MT. Angulated and bifurcating clots are associated with poorer rates of successful reperfusion.

Keywords: clot; endovascular recanalization; magnetic resonance imaging; stroke; thrombectomy.

Figure 1

Illustrations of SVS shape in an angulated (A-shaped) branch [either in an MCA bifurcation [a], or an angulated M1–M2 [b]] or in a straight [S-shaped [c]] branch. (A) Susceptibility vessel sign in a M1 segment seen as a linear hypo-intensity branch, dividing into two clots within the M2 middle cerebral artery branches. (B) Susceptibility vessel sign in a M1 segment seen as a horizontal hypo-intensity in the M1 branch, continuing with a 90° angle in the M1/M2 branch. (C) Susceptibility vessel sign in a M1 segment seen as a linear/straight hypo-intensity in the M1 branch (I).

Figure 2

Flow-chart. Number of patients screened then included according to our inclusion criteria: Initial database 352 patients; among them 172 had a proximal MCA (M1) occlusion; 101 of them were screened by MRI, and 71 were screened by CT scan and excluded; 62 patients had A SVS on their GRE imaging.