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 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 Among 29 patients with eTICI 2c-3 (median age, 73 years; 48% female), 6 (21%) showed no-reflow changes at TP1 and 7 (24%) showed global no-reflow at TP2. Between TP1 and TP2, no-reflow persisted in 3 patients, progressed in 1, resolved in 2, and newly developed in 3. Global no-reflow at TP1 was associated with greater infarct growth at TP2 (median difference 25.02 mL, 95% CI 5.60-44.43, p = 0.01). Global no-reflow at TP2 was associated with lower odds of good clinical outcome (mRS score 0-1: odds ratio 0.14, 95% CI 0.02-0.84, p = 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.