Abstract TP90: Computed Tomography Perfusion Mismatch is Stable Over Time From Onset After Stroke Due to Underestimation of Core Infarct in Late Time Window

Abstract

Background: Automated computed tomography perfusion (CTP) imaging is proven effective at selecting patients with acute large vessel occlusion (LVO) for endovascular intervention in the extended time window (>6 hours after last known normal [LKN]). However, there are limited data on the likelihood of identifying core infarct-penumbral mismatch in the late time window. Hypothesis: Automated CTP mismatch ratios (Time-to-maximum residue function [T max ] >6s: relative cerebral blood flow [rCBF] <30%) using RAPID software will decrease as time from LKN increases. Methods: We reviewed a retrospective registry of consecutive patients with LVO who underwent CTP within 24h of LKN at 3 academic hospitals between 06/2017 - 12/2017. Unenhanced CT and CTP parameters were compared between patients who presented within 12h of LKN versus 12-24h of LKN. Results: Among 60 included patients, the median age was 78 years (IQR 64-84), 36 (60.0%) were female, and 39 (65.0%) underwent thrombectomy. Patients who presented at 12-24h had poorer ASPECTS scores than patients who presented <12h from LKN (median score 7 [IQR 5-8] vs. 8 [IQR 6-9], p=0.092), but the mismatch ratios were not significantly different (median 5.95 [IQR 2.64-9.11] vs. 3.28 [IQR 2.19-7.70], p=0.509). Longer delay from LKN were associated with a lower ASPECTS score (adjusted β -0.12 points/hr, 95%CI -0.21 - -0.04, p=0.006), which was driven by patients with witnessed symptom onset (adjusted p=0.009; Figure), but no significant change in rCBF <30% (adjusted p=0.360) irrespective of whether symptom onset was witnessed (adjusted p=0.847; Figure). Conclusions: As time progresses in acute anterior LVO, the unenhanced CT may be more sensitive than rCBF<30% for detecting the volume of irreversibly damaged tissue. Figure caption: ASPECTS and rCBF <30% over time. Blue dots indicate patients with witnessed onset (with fitted dashed line), red circles indicate patients with unwitnessed onset (with fitted solid line).