Tissue hypoperfusion after endovascular thrombectomy and functional outcome across heterogeneous imaging definitions: a systematic review and meta-analysis

Purpose Successful macrovascular recanalization after endovascular thrombectomy (EVT) does not invariably result in effective tissue reperfusion. Persistent post-EVT tissue hypoperfusion has been associated with poor outcome but is defined heterogeneously across imaging studies. We investigated whether its prognostic relevance remains consistent across different operational definitions. Methods We systematically identified studies enrolling adults with anterior-circulation large vessel occlusion who underwent EVT with successful macrovascular recanalization (mTICI/eTICI≥2b), received post-EVT perfusion imaging and had an explicit imaging-based definition of persistent tissue hypoperfusion, impaired microvascular reperfusion, or no reflow. Studies reporting modified Rankin Scale (mRS)-based functional outcomes at approximately 30 or 90 days were included. Random effects meta-analyses were performed using the Hartung-Knapp adjustment. Results Six studies (404 patients) were included in the quantitative analysis. Despite substantial heterogeneity in perfusion metrics, spatial definitions, imaging timing, and recanalization thresholds, post-EVT hypoperfusion was associated with lower odds of favorable functional outcome (OR 0.28, 95% CI 0.18-0.46). The association was observed for both mRS 0-2 or mRS 0-1 definitions of favorable outcome. No significant subgroup differences were observed according to perfusion metric or recanalization threshold. The direction of the association remained consistent in leave-one-out analyses. Conclusions The prognostic association of post-EVT tissue hypoperfusion persisted despite substantial heterogeneity in its operational definition, suggesting that its clinical relevance may extend beyond any single imaging surrogate of microvascular no reflow. A broader and standardized operational definition may be useful for prognostic assessment and enrichment of patients for future trials.