Background Determining infarct progression rate in acute ischemic stroke (AIS) is important for patient triage, treatment decision-making, and outcome prognostication.

Objective To estimate infarct progression rate in patients with AIS with large vessel occlusion (LVO) and determine its predictors and impact on clinical outcome.

Methods Data are from the ESCAPE-NA1 Trial. Patients with AIS with time from last known well to randomization <6 hours and near-complete reperfusion following endovascular treatment were included. Infarct growth rate (mL/h) was estimated by dividing 24 hour infarct volume (measured by non-contrast CT or diffusion-weighted magnetic resonance imaging) by time from last known well to reperfusion. Multivariable linear regression was used to assess the association of patient baseline variables with log-transformed infarct progression rate. The association of infarct progression rate and good outcome (modified Rankin Scale score 0–2) was determined using multivariable logistic regression.

Results Four hundred and nine patients were included in the study. Median infarct progression rate was 4.74 mL/h (IQR 1.25–14.84). Collateral status (β: −0.81 (95% CI −1.20 to −0.41)), Alberta Stroke Program Early CT Score (ASPECTS, β: −0.34 (95% CI −0.46 to −0.23)), blood glucose(β: 0.09 (95% CI 0.02 to 0.16)), and National Institutes of Health Stroke Scale (NIHS score (β: 0.07 (95% CI 0.04 to 0.10)) were associated with log-transformed infarct progression rate. Clinical and imaging baseline variables explained 23% of the variance in infarct progression rate. Infarct progression rate was significantly associated with good outcome (aOR per 1 mL/h increase: 0.96 (95% CI 0.95 to 0.98)).

Conclusion In this sample of patients presenting within the early time window with LVO and near-complete recanalization, infarct progression rate was significantly associated with good outcome. A significant association between ASPECTS, collateral status, blood glucose, and NIHSS score was observed, but baseline imaging and clinical characteristics explained only a small proportion of the interindividual variance. More research on measurable factors affecting infarct growth is needed.