Functional outcomes following mechanical thrombectomy beyond 6 hours after acute ischaemic stroke

INTRODUCTION: Mechanical thrombectomy (MT) within 6 hours is the standard treatment for large vessel occlusion stroke. However, the benefit-to-risk ratio of MT becomes increasingly unfavourable in the extended 6- to 24-hour window; current guidelines recommend cerebral perfusion studies (CPS) for patient selection. Although recent trials of extended-window MT have shown promising results, challenges may arise in real-world implementation where CPS are not readily available. This single-centre retrospective review included patients who underwent extended-window MT with or without prior CPS in Hong Kong. METHODS: This study included 480 patients who underwent MT at Queen Mary Hospital between January 2019 and January 2025. Primary outcomes were 3-month modified Rankin Scale, door-to-groin puncture time, recanalisation rate, procedural complications and mortality. Secondary outcomes included differences in 3-month functional status between patients who underwent MT with or without prior CPS. RESULTS: Among the 51 patients who underwent extended-window MT, 37 (72.5%) had anterior circulation stroke. The overall complication rate was 7.8%. Cerebral perfusion studies were performed to guide selection in 15 patients (40.5%) with anterior circulation strokes and were associated with a significantly higher rate of functional independence at 3 months compared with selection based on clinical judgement alone (66.7% vs 27.3%; P=0.018). Use of CPS was also associated with a longer door-to-puncture time (167 vs 89.5 min; P<0.001). CONCLUSION: Cerebral perfusion studies improve patient selection for extended-window MT. Favourable functional outcomes were achieved in a substantial proportion of patients selected on the basis of clinical criteria alone. The study findings provide evidence supporting clinical service development to facilitate CPS adoption and extended-window MT in Hong Kong.