Abstract 40: Relationship of Collateral Status With Clinical Outcomes in Endovascular Thrombectomy for Large Core Stroke: A SELECT2 Subanalysis

Abstract

Background: Previous studies demonstrating association of collateral status with clinical outcomes after endovascular thrombectomy (EVT) excluded patients with large core infarcts. We analyzed the association of collateral status with clinical outcomes and EVT treatment effect in SELECT2. Methods: In SELECT2, a central core lab adjudicated CT-angiographic collateral status using collateral scores (CS) by Tan et al. Patients were stratified based on CS into poor (CS 0-1) vs good (CS 2-3) collaterals. The primary outcome was the distribution of modified Rankin Scale score at 90-day follow-up. Models were adjusted for core volume, ASPECTS in addition to age, stroke severity and time to randomization. Results: Of 352 patients, 180 received EVT. Median collateral status was 2(IQR 1-2). Patients presenting <6h after last known well (LKW) (n=100) had poorer collaterals than those presenting at 6-24 hours (n=252), median 1 (1-2) vs 2 (1-2), p<0.001. Collateral status inversely correlated with CTP core volume (Rho=-0.32, p<0.0001), but not with CT ASPECTS (Rho=0.07, p=0.16). Overall, point estimates favored EVT in patients with poor (CS 0-1) [aGenOR: 1.32, 95% CI: 0.98-1.79, p=0.068] and good (CS 2-3) collaterals [aGenOR: 1.97, 95% CI: 1.43-2.72, p<0.001] without significant heterogeneity [p-interaction=0.094]. However, in the earlier 0-6h time window, there was evidence of treatment effect hetermogeneity with a larger treatment effect when good collaterals were present [aGenOR: 4.10, 95% CI: 1.81-9.29] and an absent treatment effect when only poor collaterals were observed [aGenOR: 1.26, 95% CI: 0.79-1.99], p-interaction=0.023. In the late time window, (6-12h), the EVT treatment effect did not differ significantly between poor collaterals (aGenOR: 1.35, 95% CI: 0.91-2.01) and good collaterals (aGenOR: 1.78, 95% CI: 1.24-2.56, p-interaction=0.50). Conclusion: Collateral status was worse in large core patients presenting in early (<6 hours) window; and correlated with ischemic core volume but not ASPECTS. Collaterals status modified EVT treatment effect in the early but not the late time window, in which both good and poor collaterals still benefited from EVT. Clinicaltrials.gov registration: NCT03876457