Association between the no-reflow phenomenon and clinical outcomes after endovascular treatment for acute ischemic stroke: A systematic review and meta-analysis.

Background
The no-reflow phenomenon, characterized by impaired microvascular reperfusion despite successful macrovascular recanalization, has been identified as a potential contributor to poor outcomes in acute ischemic stroke (AIS) treated with endovascular therapy (EVT). This systematic review and meta-analysis aimed to assess the prevalence and clinical impact of no-reflow phenomenon in AIS patients undergoing EVT.Methods
We conducted a systematic review and meta-analysis of randomized controlled trials (RCTs) and observational studies reporting the no-reflow phenomenon after EVT. Databases searched included PubMed, Embase, and CENTRAL (inception to February 9, 2025). Outcomes included no-reflow prevalence, functional outcomes (mRS), early neurological recovery, infarct volume, hemorrhagic complications, and 90-day mortality. Pooled risk ratios (RR) or mean differences (MD) were calculated using random-effects meta-analysis, and heterogeneity was assessed with I2.Results
Eight studies (n = 1483 patients) were included. The pooled prevalence of no-reflow was 20.5% (95% CI 6.2%-49.9%; I2 = 96.9%). Compared with controls, patients with no-reflow had reduced early neurological recovery (RR 0.76; 95% CI 0.64-0.90) and increased risk of hemorrhagic transformation (RR 1.82; 95% CI 1.18-2.79) and symptomatic intracranial hemorrhage (RR 1.88; 95% CI 1.00-3.56). Differences in functional independence (mRS 0-2) and mortality were not statistically significant. Subgroup analyses based on study design revealed divergent patterns, particularly for infarct volume, which was significantly greater in no-reflow patients in post-hoc RCTs but not in the overall analysis.Conclusion
No-reflow affects one in five EVT-treated patients and is associated with adverse neurological and hemorrhagic outcomes. Findings highlight the need for standardized definitions and prospective trials to clarify its clinical impact.