Abstract 6: Response to Thrombolysis Treatment in Ischemic Stroke Patients With and Without Arterial Occlusion on Computed Tomographic Angiography: The Third International Stroke Trial

Abstract

Background: The Third International Stroke Trial (IST-3) is a multicenter, randomised open label blinded outcome assessment controlled trial (RCT) testing i.v. thrombolysis (rt-PA) given within 6 hours of ischemic stroke: 3035 patients in whom indications for rt-PA were uncertain were randomised to rt-PA 0.9mg/kg or control after plain brain imaging. We also collected CT angiography (CTA) scans from centers where this was routinely performed. We tested whether the presence or absence of arterial occlusion on CTA influenced the effect of rt-PA on 6-month Oxford Handicap Score (OHS). Methods: We included all IST-3 patients with pre-randomisation CTA. One observer analysed all CTAs blind to follow-up imaging and all clinical data. We tested the association between CTA-identified arterial occlusion and 6-month OHS, with and without rt-PA, in an ordinal regression model with age, National Institutes of Health Stroke Scale (NIHSS) and time from onset as covariates. Odds ratios (OR) for the effect of rt-PA on OHS in those with vs without CTA arterial occlusion were compared. Results: Pre-randomisation CTA was performed in 272/3035 patients (44.5% male, median age 81 years, IQR 71-86). CTA showed arterial occlusion in 42% (115/272). CTA-demonstrated arterial occlusion at randomisation reduced the odds of good outcome (OR 0.43, 95%CI 0.25-0.76, p=0.003). The effect of rt-PA on good outcome did not differ significantly between patients with (OR 1.60, 0.71-3.63, p=0.260) vs. without (OR 0.89, 0.50-1.57, p=0.684) CTA occlusion (p-value for difference 0.249) although the direction of effect differed. Conclusion: Patients with arterial occlusion on CTA had worse 6-month outcome but we did not find a significant rt-PA-occlusion interaction in these patients. However the sample size limits detection of a modest interaction. The suggestion that patients with occlusion might benefit more could be tested in individual meta-analysis to achieve a larger sample size.