Purpose The Penumbra Pivotal Stroke Trial reported a 25% good outcome rate (modified Rankin Scale (mRS) ≤2) despite 81% recanalization rate. We evaluated whether a good initial non-contrast CT (Alberta Stroke Programe Early CT Score (ASPECTS) >7) and a short time to recanalization predicted good clinical outcome in this trial.

Materials and methods Data were from the Penumbra Pivotal Stroke Trial. Baseline scans were evaluated by two experienced readers blinded to clinical outcomes using an ASPECTS scoring system. ASPECTS was dichotomized into >7 and ≤7 for the primary analysis. Data on the degree of recanalization based on TIMI scores, stroke onset to recanalization time and CT to recanalization time were obtained. The primary clinical outcome was mRS ≤2 at 3 months.

Results Median baseline NIHSS was 18 (range 8–34) and median baseline ASPECTS was 6 (range 0–10). 81.2% achieved recanalization (TIMI 2–3) and 27.1% good clinical outcome. There was no difference in baseline characteristics between the groups with ASPECTS >7 and ≤7 except in history of hypertension (more common in the >7 group, p=0.01). No difference in TIMI 2–3 recanalization (83.9% vs 79.6%; p=0.8), onset to recanalization (390 vs 359 min; p=0.6) or CT to recanalization time (223.8 vs 208 min; p=0.6) was noted between these two groups. Good clinical outcome however was significantly higher in the >7 group compared with the ≤7 group (50% vs 15%, risk ratio 3.3, 95% CI 1.6 to 6.8; p=0.0001). No patient with an ASPECTS score ≤4 (n=28) or without recanalization (TIMI 0–1) (n=16) had good clinical outcome. There was evidence of an interaction between baseline ASPECTS (dichotomized as >7 and ≤7) and onset to recanalization time (dichotomized as ≤300 min and >300 min) in predicting good clinical outcome (p=0.06).

Conclusion Patients with a low baseline CT (ASPECTS ≤4) do not benefit from recanalization at any time point. Patients who do not recanalize do not benefit at all. Fast recanalization may benefit even patients with evident damage on the CT scan (ASPECTS >4). Only patients with very favorable scans (ASPECTS >7) benefit when recanalization is late. Patients benefit the most when they are recanalized rapidly and have a favorable baseline CT scans (ASPECTS>7).