Related Experiment Video
Updated: Mar 20, 2026
The Stroke Preclinical Assessment Network Multi-laboratory Model of Thromboembolic Stroke with Thrombolysis: TE-MCAo
Published on: December 19, 2025
The role of collateral circulation in extended-window mechanical thrombectomy: a systematic review and meta-analysis
Khalil St Brice1, Tariq Parker2, Emmanuel Mensah3
1Faculty of Medical Sciences, University of the West Indies, St. Augustine, Trinidad and Tobago.
Background:
Endovascular thrombectomy (EVT) has transformed acute ischemic stroke (AIS) management due to large vessel occlusion (LVO), markedly improving outcomes within 6 h of symptom onset. The DAWN and DEFUSE-3 trials extended EVT eligibility to 6-24 h, shifting selection from time-based to imaging-based criteria. However, the role of collateral circulation in this extended-window remains uncertain. This study evaluated whether collateral status influences EVT outcomes beyond six hours from symptom onset.
Methods:
A systematic review and meta-analysis was conducted per PRISMA guidelines, including randomized controlled trials (RCTs) comparing EVT to medical management in the extended window (6-24 h). Collateral status was categorized as good or poor based on definitions used in the original studies. Eligible studies enrolled AIS patients with LVO and collateral grading. The primary outcome was functional independence (modified Rankin Scale score 0-2 at 90 days). A random-effects model was used to calculate pooled odds ratios (ORs), with subgroup analyses based on collateral status (good vs. poor).
Results:
Five RCTs involving 718 patients (EVT = 358, medical management = 360) were included. EVT significantly improved functional independence (OR 5.38, 95% CI: 3.73-7.76, P = 0.0002, I2 = 0%). Only two trials reported outcomes stratified by collateral status (EVT = 142, medical management = 142). EVT improved functional independence in both patients with good collaterals (OR 6.09; P = 0.005) and poor collaterals (OR 8.67; P = 0.04), with no statistically significant difference between subgroups (P = 0.65).
Conclusion:
EVT significantly improves functional independence (mRS 0-2 at 90 days) in extended window (6-24 h) mechanical thrombectomy, and available subgroup data suggest this benefit may extend to both good and poor collaterals. These results support offering EVT based on overall clinical and imaging context. The generalizability of these findings is limited due to the small number of studies.
Registration:
This review was not registered in PROSPERO.
