Abstract WP47: Dynamic Changes in MR-Defined Collateral Flow After Acute Ischemic Stroke is Associated With Larger Penumbral Signature and Improved Clinical Outcomes

Abstract

Introduction: Collateral flow is postulated to play an important role in maintaining tissue viability during acute ischemic stroke (AIS), but its direct influence on the ischemic penumbra and eventual tissue outcome is not well understood. Hypothesis: We hypothesized that collateral flow is dynamic during the first 24h after AIS and that successful collateralization is associated with improved outcomes. Methods: We retrospectively analyzed data from a prospectively collected observational MRI study of AIS patients serially imaged at 3h (n=51), 6h (n=45), 24h (n=26), and 1 month (n=36) after stroke onset. Collateral flow was assessed with dynamic susceptibility contrast-enhanced MRI for all time-points, utilizing a previously validated method (Kim et al, 2014; grade 1=poor - grade 4=excellent). Clinical outcome (NIHSS, mRS) and tissue outcome were based on 1-month assessments and FLAIR imaging. Results: Collateral flow was dynamic during the first 24h after stroke onset, changing in 33% of patients between 3-6h, and 68% between 6-24h. Moreover, the majority of patients (62%) showed improved collaterals during the first 24h (at 3h, 12% of patients had grade 1 and 22% grade 4; at 24h, 8% had grade 1 and 35% had grade 4). At 3 and 6h there was an inverse relationship between collateral grades 1 and 4 and percent diffusion-perfusion mismatch (p= 0.0006 and 0.0015, respectively). Patients with grade 4 collaterals at 3h had greater relative improvement in NIHSS at one month compared to grade 1 (p= 0.0363). In addition, those with improving collaterals within the first 24h were more likely to have a good outcome (mRS 0-2; p= 0.0171; Figure). Conclusions: Collateral flow is dynamic in the first 24h post-stroke, and improved collateralization is associated with better radiographic and clinical outcomes