Temporal Dynamics of the No-Reflow Phenomenon on Serial Perfusion MRI After Thrombectomy

BACKGROUND AND OBJECTIVES: The no-reflow phenomenon, observed in up to 30% of patients with ischemic stroke despite technically successful thrombectomy, is associated with poor outcomes. However, its temporal evolution remains uncharacterized. Understanding its progression is essential to inform the development of adjunctive therapies aimed at improving outcomes after recanalization. The objective of this study was to characterize the temporal dynamics of no-reflow using serial post-thrombectomy MR perfusion imaging. METHODS: In a multicenter prospective observational study, 67 consecutive adult patients with acute anterior large vessel occlusion underwent serial post-thrombectomy perfusion MRI at 2 hours (time point 1, TP1) and 24-48 hours (time point 2, TP2) after the procedure. Key exclusions were inability to tolerate MRI, expanded Treatment in Cerebral Ischemia (eTICI) scores <2c, and missing or poor-quality imaging. The primary outcome was the presence of no-reflow at TP1 and/or TP2, defined as visually detectable hypoperfusion within the infarct with >15% interside median relative cerebral blood volume or flow reduction after eTICI 2c-3 angiographic reperfusion. No-reflow was assessed globally (across the entire diffusion-weighted imaging-positive lesion at TP2) and within 2 subregions (early ischemic core and infarct growth). The associations between no-reflow patterns, infarct growth, and favorable clinical outcome (modified Rankin Scale [mRS] scores 0-1 at 3 months) were examined as exploratory analyses. RESULTS: = 0.03). DISCUSSION: No-reflow manifests early after technically successful thrombectomy and frequently persists, possibly contributing to infarct growth and worse patient outcomes. Cases of resolution and progression suggest a dynamic and reversible pathology, potentially amenable to timely treatment. TRIAL REGISTRATION INFORMATION: ACTRN12624000629538.