Abstract WP117: Improvement of Collateral Status in Thrombectomy-Eligible Stroke Patients During Inter-Hospital Transfer: Association With Clinical Factors and Outcome

Abstract

Background: Ischemic stroke patients who are eligible for endovascular therapy (EVT), can be transferred from a primary stroke center (PSC) to an EVT-capable comprehensive stroke center (CSC). Little is known about the dynamics of the collateral circulation in this time-window. We aimed to explore changes in collateral status during inter-hospital transfer among patients with poor collaterals on presentation to the PSC. Methods: Data from patients with an anterior circulation large vessel occlusion (LVO), transferred to two CSCs were prospectively collected. A CT perfusion was obtained at the PSC followed by an MRI immediately on arrival at the CSC. The hypoperfusion intensity ratio (HIR), a measure of collateral blood flow, was calculated as the ratio of the Tmax volumes of >10s and >6s. Only patients with stable LVO at the CSC and poor collateral status at the PSC (HIR ≥ 0.40) were included. An HIR < 0.40 in the CSC and a difference ≥ 0.10 was considered as HIR improvement. Results: Data from 104 patients with perfusion imaging at both PSC and CSC, were analyzed. Of them, we included 59 patients with an HIR ≥ 0.40 at the PSC. Sixteen (27%) patients experienced HIR improvement during transfer (Figure 1) . A smaller baseline core volume was independently associated with HIR improvement (OR for every 10 ml increase = 0.46 {95%CI 0.21-0.81}; p=0.03). Collateral improvement was associated with slower infarct growth during transfer (2.45 {95%CI 1.03-3.62} vs 7.77 {95%CI 4.56-17.86} ml/h; p<0.01) and a better functional outcome at 90 days post stroke (median mRS 3 {IQR 1-5} vs 4 {IQR 4-6}; p=0.01). Conclusion: During inter-hospital transfer spontaneous improvement in collateral status, as measured by HIR, is commonly seen, and associated with a smaller infarct core at the PSC, slower infarct growth during transfer, and better functional outcomes. Future neuroprotective trials targeted at collateral improvement, might consider the use of the HIR change as a surrogate outcome marker.