Prevalence and Significance of Impaired Microvascular Tissue Reperfusion Despite Macrovascular Angiographic Reperfusion (No-Reflow)

Background The relevance of impaired microvascular tissue-level reperfusion despite complete upstream macrovascular angiographic reperfusion (no-reflow) in human stroke remains controversial. We investigated the prevalence and clinical-radiological features of this phenomenon, and its associations with outcomes in three international randomized controlled thrombectomy trials with pre-specified follow-up perfusion imaging. Methods In a pooled analysis of the EXTEND-IA (ClinicalTrials.gov number NCT01492725), EXTEND-IA TNK (NCT02388061) and EXTEND-IA TNK Part-two (NCT03340493) trials, patients undergoing thrombectomy with final angiographic extended Thrombolysis In Cerebral Ischemia 2c-3 score for anterior circulation large vessel occlusion and 24-hour follow-up CT or MRI perfusion imaging were included. No-reflow was defined as regions of visually demonstrable persistent hypoperfusion on relative Cerebral Blood Volume or Flow maps within the infarct and verified quantitatively by >15% asymmetry compared to a mirror homologue in the absence of carotid stenosis or re-occlusion. Results Regions of no-reflow were identified in 33 of 130 patients (25.3%), encompassed a median of 60.2% (Interquartile range 47.8-70.7%) of the infarct volume, and involved both subcortical (n=26/33,78.8%) and cortical (n=10/33,30.3%) regions. Patients with no-reflow had a median 25.2% ([Interquartile range 16.4-32.2%],p