Supplementary Material for: Determination of the Onset-to-Reperfusion Time Threshold in Mechanical Thrombectomy Patients with Good Collateral Flow

Introduction: Mechanical thrombectomy (MT) is an effective treatment for acute ischemic stroke caused by large vessel occlusion. Prior investigations have shown that a well developed collateral circulation preserves the ischemic penumbra more effectively than inadequate collateral flow. As a result, stroke patients with robust collaterals generally achieve more favorable functional outcomes after MT. However, it remains unclear how long robust collateral flow can preserve the penumbra. This study aimed to determine the onset-to-reperfusion time threshold within which good collaterals improve outcomes. Methods: We retrospectively analyzed patients with acute ischemic stroke who achieved successful reperfusion (expanded Thrombolysis in Cerebral Infarction ≥ 2b) after MT between 2017 and 2023. Collateral status was graded with the ASITN/SIR scale and categorizing patients into good collateral (grades 2–4) and poor collateral (grades 0–1) group. The primary endpoint was excellent functional outcome, defined as a 90 day modified Rankin Scale (mRS) score of 0–1. We used receiver operating characteristic curve analysis to predict excellent outcomes, determining cut-off points for onset-to-reperfusion time using the Youden index. Additionally, the onset-to-reperfusion time was divided into quartiles based on the distribution of all cases, and excellent outcome rates were compared across these quartiles. Results: A total of 77 patients were included (good collateral group, 46; Poor collateral group, 31), with a median onset-to-reperfusion time of 310 min (interquartile range, 200–621 min). In the good collateral group, the cutoff time for achieving excellent outcomes was 235 min (sensitivity, 88%; specificity, 62%). The good collateral group showed significantly higher excellent outcome rates than the PC group at the shortest interval (< 200 min). Conclusion: In patients with good collateral flow who achieved reperfusion after MT, the onset-to-reperfusion time threshold associated with an excellent outcome was 235 min. The 235 min cut off may serve as a practical target for onset to reperfusion timing in patients with favorable collateral circulation undergoing MT.