Some patients with large vessel occlusion (LVO) are first evaluated at primary stroke centers (PSCs) before transfer to a comprehensive stroke center (CSC) for endovascular thrombectomy (EVT). A subgroup of these patients experiences rapid infarct growth, also known as “imaging decay,” during transfer, limiting the benefit from intervention. We evaluated the incidence, predictors and outcomes of imaging decay in this subgroup.

The present study was an analysis of all patients with anterior circulation LVO at PSCs in Northern Alberta and transferred to the CSC in the University of Alberta Hospital in Edmonton for EVT. The Alberta Stroke Program Early CT Score (ASPECTS) decay was defined as ≥ 2 ASPECTS points decrement at CSC compared to PSC. The primary outcome was 90-day home time.

182 patients were included. Median time between baseline and follow-up CTs was 250.5 (IQR 163–324.25) minutes. Out of the 182 patients, 66 patients (36%) had ASPECTS decay, and 32 of 66 patients (48%) underwent EVT. Poor collateral score was strongly associated with ASPECTS decay (OR = 0.35, [0.21–0.59], p < 0.001). Patients with ASPECTS decay have a significantly lower 90-day home time (β = –0.32, [–4.6 to –36.4], P < 0.001) and higher risk of 90-day mortality (OR = 4.9, [2.4–10.0], P < 0.001) and in-hospital death (OR = 3.8, [1.2–12.3], P = 0.03).

For patients with LVO transferred for thrombectomy, a third of our patients developed ASPECTS decay. Collateral blood flow was the main determinant of ASPECTS decay during interfacility transfers. Decay is strongly associated with poor functional outcomes.