No-reflow phenomenon in stroke patients: a systematic literature review and meta-analysis of clinical data.

BackgroundThe no-reflow phenomenon refers to the absence of microvascular reperfusion despite macrovascular reperfusion.AimThe aim of this analysis was to summarize the available clinical evidence on no-reflow in patients with acute ischemic stroke.MethodsA systematic literature review and a meta-analysis of clinical data on definition, rates and impact of the no-reflow phenomenon after reperfusion therapy was carried out. A predefined research strategy was formulated according to the PICO model and was used to screen for articles in PubMed, MEDLINE and Embase up to September 8, 2022. Whenever possible, quantitative data were summarized using a random-effects model.ResultsThirteen studies with a total of 719 patients were included in the final analysis. Most studies (n=10/13) used variations of the Thrombolysis in Cerebral Infarction scale to evaluate macrovascular reperfusion, whereas microvascular reperfusion and no-reflow were mostly assessed on perfusion maps (n=9/13). In one third of stroke patients with successful macrovascular reperfusion (29%, 95% CI 21-37%) the no-reflow phenomenon was observed. Pooled analysis showed that no-reflow was consistently associated with reduced rates of functional independence (OR 0.21, 95% CI 0.15-0.31).ConclusionThe definition of no-reflow varied substantially across studies but it appears to be a common phenomenon. Some of the no-reflow cases may simply represent remaining vessel occlusions and it remains unclear whether no-reflow is an epiphenomenon of the infarcted parenchyma or causes infarction. Future studies should focus on standardizing the definition of no-reflow with more consistent definitions of successful macrovascular reperfusion and experimental set-ups that could detect the causality of the observed findings.