Abstract WMP21: Underestimation of Ischemic Core on Perfusion CT in Patients With Acute Large Vessel Occlusion: Results From the BEST Prospective Cohort Study

Abstract

Background: The 2018 AHA guidelines recommend patients with acute large vessel occlusion (LVO) be considered for thrombectomy in the 6 to 24-hour window based on perfusion imaging. Within 6 hours, CT perfusion (CTP) core estimates may underestimate volume of irreversible infarction visualized on the unenhanced CT; however this has not been well characterized in later time windows. Methods: Using a multi-center prospective cohort of consecutive patients who underwent thrombectomy for LVO 0-24 hours after last known normal, we correlated baseline CTP core infarct volume (rCBF<30%) and unenhanced CT ASPECTS score, as recorded by local investigators. We compared CTP findings between patients with an unfavorable ASPECTS (<6) against those with a favorable ASPECTS (≥6), and assessed findings over time. Results: Of 443 enrolled patients, 165 who underwent CTP were included (median age 69y [IQR 57-80], 83 [50%] female, with a median ASPECTS of 8 [IQR 6-9] and core of 9cc [IQR 0-28]). ASPECTS and core volume moderately correlated (r=-0.35, p<0.01). An absent core (0cc) was observed in 52/165 (32%) patients, among whom the median ASPECTS score was 8 (IQR 8-10). Of the 28 patients with unfavorable ASPECTS, 3 had a normal core volume (11%, 95%CI 2 - 28%). As time to recanalization progressed, the ASPECTS score worsened (common OR 1.05, 95%CI 1.01-1.09, p=0.02) whereas the core (p=0.66) and penumbra volumes (p=0.70) remained unchanged. After adjustment for age and baseline NIHSS, the decline in ASPECTS remained significant (cOR 1.05, 95%CI 1.01-1.10, p=0.01), while the core (p=0.69) and penumbra volumes (p=0.74) remained unchanged. Conclusion: In this multi-center prospective cohort of patients who underwent thrombectomy, one-third of patients had normal core infarct volumes despite half of these patients showing irreversible infarction on the unenhanced CT (ASPECTS ≤8). As time progresses, the unenhanced CT demonstrates evolution of irreversible infarction, whereas the perfusion core appears static. This finding emphasizes the need to carefully assess both unenhanced CT and CTP when considering thrombectomy eligibility in the late time window, as was required by both DAWN and DEFUSE 3 selection criteria.