Effectiveness of collateral status on clinical outcomes in patients with established large infarct: a prospective cohort study.

Background: The specific association of collateral status on outcomes in patients with large ischemic stroke (ASPECTS ≤ 5) remains unclear. This study aimed to investigate the association between collateral status and outcomes in patients who received endovascular therapy (EVT) and assess whether collateral status modifies the effectiveness of bridging intravenous thrombolysis (IVT) before EVT.

Materials And Methods: This subanalysis of a prospective cohort study enrolled patients with large vessel occlusion and ASPECTS 0-5 from 38 stroke centers across China between November 2021 and February 2023. Collateral status was graded using the American Society of Interventional and Therapeutic Neuroradiology/Society of Interventional Radiology (ASITN/SIR). The primary outcome was favorable functional outcomes at 90 days (defined as modified Rankin Scale [mRS] scores of 0-3). Safety outcomes included the incidence of symptomatic intracranial hemorrhage (ICH) within 48 h, mortality within 90 days, and any ICH within 48 h.

Results: Among 490 patients who received EVT, 34.5% (169 of 490) achieved moderate collateral and 16.7% (82 of 490) achieved good collateral. Compared to patients with poor collateral, good and moderate collateral were associated with higher odds of favorable functional outcomes and reduced rates of ICH and mortality. The effectiveness of bridging IVT prior to EVT was modified by collateral status (p for interaction = 0.039). Specifically, in patients with moderate collateral, IVT prior to EVT was associated with higher odds of favorable functional improvement (adjusted OR: 2.387, 95% CI: 1.052-5.416, p = 0.037).

Conclusion: In patients with large ischemic stroke undergoing EVT, good collateral status was associated with favorable functional outcomes, while those with moderate collateral may benefit from bridging therapy.