Single-phase CT angiography predicts ASPECTS decay and may help determine when to repeat CT before thrombectomy.

OBJETIVES: Time is relative in large-vessel occlusion acute ischemic stroke (LVO-AIS). We aimed to evaluate the rate of inter-hospital ASPECTS decay in patients transferred from a primary (PSC) to a comprehensive stroke center (CSC); and to identify patients that should repeat computed tomography (CT) before thrombectomy. MATERIALS AND METHODS: This was a retrospective cohort study of consecutive anterior circulation LVO-AIS transferred patients. The rate of ASPECTS decay was defined as (PSC-ASPECTS - CSC-ASPECTS)/hours elapsed between scans. Single-phase CT angiography (CTA) at the PSC was used to classify the collateral score. We compared patients with futile versus useful CT scan re-evaluation. RESULTS: We included 663 patients, of whom 245 (37.0%) repeated CT at a CSC. The median rate of ASPECTS decay was 0.4/h (0.0-0.9). Patients excluded from thrombectomy after a CT scan repeat (n=64) had a median ASPECTS decay rate of 1.18/h (0.83-1.61). Patients with absent collateral circulation had a median rate of 1.51(0.65-2.19). The collateral score was an independent predictor of the ASPECTS decay rate (aß = -0.35; 95%CI -0.45 - -0.19, p<0.001). Age (aOR: 1.04 95% CI 1.02-1.07, p<0.001), NIHSS (aOR: 1.11 95% CI 1.06-1.15, p<0.001), PSC ASPECTS (aOR: 0.74 95% CI 0.60-0.91, p=0.006) and the CTA collateral score (aOR: 0.14 95% CI 0.08-0.22, p<0.001) were independent predictors of the usefulness of a CT scan repeat. CONCLUSIONS: The rate of ASPECTS decay can be predicted by the CTA collateral score, helping in the selection of patients that would benefit from repeating a CT assessment on arrival at the CSC.