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

Abstract

Ng et al.1 recently reported a 25% prevalence of hypoperfusion—a >15% reduction of cerebral blood flow (CBF) or cerebral blood volume (CBV) from the mirror region on CT perfusion imaging—within the 24-hour infarct window, despite complete anterior circulation recanalization (TICI 2c/3), which negatively affected functional outcome. These findings contrast with our earlier finding of 6% (2/33) hypoperfused infarcts, where the 24-hour arterial spin labeling (ASL)-CBF images were analyzed according to the Alberta Stroke Program Early CT Score (ASPECTS) template.2 We have reanalyzed our data set considering the entire middle cerebral arterial (MCA) territory, irrespective of ASPECTS. After excluding areas with confluent hemorrhagic transformation or parenchymal hematoma on the 24-hour MRI, consensus by 2 raters (kappa = 0.752) identified only 2 additional patients exhibiting patchy mild-to-moderate hypoperfusion with volumes too small to be reliably measured on ASL images, for a total prevalence of 4 of 33 patients (12%). After excluding patients with missing mRS (n = 2) or associated infarcts outside the MCA territory (n = 5), univariate analysis showed no significant association of “no-reflow” presence with a 3-month mRS of 0–1 or 0–2. A multivariate analysis was precluded by low occurrence of no-reflow. Taken together with this article and another recent report,3 the prevalence of no-reflow after recanalized MCA stroke appears to stand ∼15–20%, depending on the perfusion modality used, and often involves small areas. The true impact on clinical outcome remains unclear.3