Abstract 165: CT Perfusion Collateral Score Predicts Which Patients Will Maintain a Penumbral Profile on MRI for Greater than 24 Hours

Abstract

Introduction: The DAWN and DEFUSE 3 trials demonstrated efficacy of endovascular treatment in patients selected using perfusion imaging or MR Diffusion Weighted Imaging (DWI) and treated up to 24h after stroke onset. Hypothesis: We hypothesized that a persistent favorable perfusion profile (target mismatch, which indicates the presence of penumbral tissue) exists in some patients beyond 24h from onset and can be predicted by lower baseline hypoperfusion intensity ratio (HIR, proportion of Tmax >6s lesion having >10s delay), which indicates favorable collaterals. Methods: We identified control arm patients from the DEFUSE 3 trial with a DWI and perfusion MRI performed 24h following randomization and defined 3 subgroups: Group 1) patients with spontaneous reperfusion; Group 2) persistent hypoperfusion lesion, but loss of the target mismatch perfusion profile; Group 3) persistent target mismatch profile. We compared group 2 with group 3 in terms of baseline, 24h and clinical outcome variables. Results: 55/90 patients in the medical arm had DWI and perfusion MRI follow-up imaging 24 hours after randomization and were included. 18% had spontaneous reperfusion, 64% had a persisting Tmax lesion with an unfavorable profile, and 18% had a persistent target mismatch profile. Patients with a persistent target mismatch profile had a significantly lower HIR on baseline imaging (0.2 vs 0.4, p<0.01) and significantly less infarct growth (15mL vs 59mL, p<0.001) than patients with loss of the target mismatch profile. The persistent target mismatch was documented a median of 38 hours after last known well time. There was no association between baseline clinical characteristics or clinical outcomes and a persistent favorable profile. Conclusions: Approximately 20% of medical arm patients in DEFUSE 3 had a persistent mismatch at a median of 38 hours after stroke onset. These patients have very slowly expanding infarcts but eventually suffer very poor clinical outcomes. Clinical trials are needed to determine if late patients presenting with penumbral tissue benefit from thrombectomy more than 24 hours from symptom onset.