Baseline National Institutes of Health stroke scale-adjusted time window for intravenous tissue-type plasminogen activator in acute ischemic stroke

Background and purpose: The effect of tissue-type plasminogen activator on functional outcome decreases progressively over time. However, given the differential pattern of arterial occlusion, stroke severity, and speed of ischemic lesion growth among candidates for reperfusion, the time window should be adjusted accordingly. We aimed to identify the impact of time-to-treatment according to stroke severity on functional outcome in patients with acute ischemic stroke.

Methods: We included 581 consecutive patients treated with alteplase according to the European Summary of Product Characteristics criteria. Patients were categorized according to National Institutes of Health Stroke Scale (NIHSS) severity in mild NIHSS (≤8), moderate NIHSS (9-15), and severe stroke NIHSS (≥16). We sequentially analyzed time-to-treatment to achieve favorable outcome (modified Rankin Scale ≤2 at 3 months).

Results: Overall, 19.8% had mild, 30.3% had moderate, and 49.9% had severe stroke. Favorable outcome occurred in 79.1%, 60.8%, and 26.2%, respectively. In patients with mild stroke, younger age (odds ratio [OR], 0.88; 95% confidence intervals [CI], 0.8-0.95), no previous history of stroke (OR, 0.16; 95% CI [0.039-0.65]), and no proximal occlusion (OR, 0.183; 95% CI [0.038-0.89]) independently predicted favorable outcome. In patients with moderate stroke, age (OR, 0.95; 95% CI [0.92-0.98]), no proximal occlusion (OR, 0.362; 95% CI [0.17-0.75]), and time-to-treatment before 120 minutes (OR, 2.70; 95% CI [1.14-6.38]) emerged as independent predictors of favorable outcome. In patients with severe stroke, younger age (OR, 0.96; 95% CI [0.94-0.99]), lower previous modified Rankin Scale (OR, 0.42; 95% CI [0.21-0.82]), and absence of proximal occlusion (OR, 0.48; 95% CI [0.25-0.94]) appeared as independent predictors.

Conclusions: The impact of time-to-treatment on favorable outcome varies widely depending on baseline stroke severity. The window for favorable outcome was ≤120 min for moderate strokes. However, time-to-treatment seemed unrelated to functional outcome in mild and severe stroke.