Outcomes of Mechanical Thrombectomy in the Early (<6-hour) and Extended (≥6-hour) Time Window Based Solely on Noncontrast CT and CT Angiography: A Propensity Score–Matched Cohort Study

Abstract

BACKGROUND AND PURPOSE: Current stroke care recommendations for patient selection for mechanical thrombectomy in the extended time window demand advanced imaging to determine the stroke core volume and hypoperfusion mismatch, which may not be available at every center. We aimed to determine outcomes in patients selected for mechanical thrombectomy solely on the basis of noncontrast CT and CTA in the early (,6-hour) and extended ($6-hour) time windows. MATERIALS AND METHODS:Consecutive mechanical thrombectomies performed for acute large-vessel occlusion ischemic (ICA, M1, M2) stroke between February 2016 and August 2020 were retrospectively reviewed. Eligibility was based solely on demographics and noncontrast CT (ASPECTS) and CTA, due to the limited availability of perfusion imaging during the study period. Propensity score matching was performed to compare outcomes between time windows. RESULTS:Of 417 mechanical thrombectomies performed, 337 met the inclusion criteria, resulting in 205 (60.8%) and 132 (39.2%) patients in the 0-to 6-and 6-to 24-hour time windows, respectively. The ASPECTS was higher in the early time window (9; interquartile range ¼ 8-10) than the extended time window (9; interquartile range ¼ 7-10; P ¼ .005). Propensity score matching yielded 112 well-matched pairs. Equal rates of TICI 2b/3 revascularization and symptomatic intracranial hemorrhage were observed. A favorable functional outcome (mRS 0-2) at 90 days was numerically more frequent in the early window (45.5% versus 33.9%, P ¼ .091). Mortality was numerically more frequent in the early window (25.9% versus 17.0%, P ¼ .096).CONCLUSIONS: Patients selected for mechanical thrombectomy in the extended time window solely on the basis of noncontrast CT and CTA still achieved decent rates of favorable 90-day functional outcomes, not statistically different from patients in the early time window.

Association between time to treatment and clinical outcomes in endovascular thrombectomy beyond 6 hours without advanced imaging selection

“…We included 3278 patients: 2610 (79.6%) treated within 6 hours (early window), and 668 (20.4%) treated between 6 to 24 hours (late window); 141 patients had significant pre-stroke disability (mRS 3–5) and 179 patients had an NIHSS score <6 on admission; 2196 patients (67.0%) had a documented precise time of stroke onset, while the remainder were documented as last known well. Compared with the early window, patients treated in the late window were younger, had a lower baseline stroke severity (NIHSS) (median 169–20 vs 1813–22), had lower rates of IV-tPA use (33.8% vs 62.9%), were more likely to undergo general anesthesia (61.5% vs 51.5%), and were more likely to be treated using a stent retriever or a combined technique of stent retriever and thromboaspiration (table 1 and online supplemental table 1). No significant differences were observed in the remaining baseline characteristics between the two time windows.…”

“…Previous observational studies assessing overall rates of functional independence (mRS ≤2) in the late EVT window have reported different results at 90-day follow-up, ranging from 20% to 64% using various pre-specified clinical and imaging patient selection criteria 8–11 18 20–23. Some of these investigations incorporated perfusion-based imaging with varying adherence to the DAWN and DEFUSE-3 eligibility criteria,18 20–23 while others used solely NCCT and CTA, but also varied in their selection criteria 8–11.…”

“…Ongoing RCTs are assessing whether treatment benefit with EVT is maintained in patients presenting beyond 6 hours of stroke onset when less restrictive clinical and imaging selection criteria are used 6 7. In the interim, functional and safety outcome data following EVT in the absence of CT perfusion or MR imaging in the late window is limited 8–11. Furthermore, while functional outcomes are highly time sensitive to EVT in the early (<6 hours) window, studies have reported a transition to a slower loss of effectiveness from EVT in the late window 12 13.…”

Evolution of Hypodensity on Non-Contrast CT in Correlation with Collaterals in Anterior Circulation Stroke with Successful Endovascular Reperfusion

“…This issue has been addressed in two recent studies by Hendrix et al [10] and Nguyen et al [11] which showed that there were no significant differences in clinical outcomes in proximal anterior stroke treated with MT in the late time window between patients selected solely with simple NCCT and those selected with advanced imaging. The authors concluded that their findings have the potential to widen the indication for treating patients in the extended window using simpler, less costly, and easier to implement NCCT imaging.…”

“…However, a recent study by Hendrix et al [10] as well as the multicentre international CLEAR trial (published by Nguyen et al in JAMA Neurology) [11] have shown that simple non-contrast CT (NCCT) alone may be just as useful as advanced imaging in selecting stroke patients with late-presenting LVO for MT, which could allow for a more pragmatic selection of patients in the extended window.…”