Does variability in automated perfusion software outputs for acute ischemic stroke matter? Reanalysis of EXTEND perfusion imaging.

AIMS We reprocessed the Extending the time for Thrombolysis in Emergency Neurological Deficits (EXTEND) perfusion imaging with a different automated software with the aim of comparing mismatch eligibility and outcomes. METHODS EXTEND baseline perfusion imaging data were reprocessed using autoMIStar software to identify patients who were eligible based on the same target mismatch criteria as per the original trial. RESULTS From the 225 patients fulfilling RAPID-based mismatch criteria randomized in the EXTEND study, 196 (87%) patients met the revised mismatch criteria. Most common reasons for not meeting revised criteria were core >70 ml (n = 9), and no perfusion lesion/lack of penumbral tissue (n = 20). The revised perfusion lesion volumes were significantly smaller compared to the original RAPID volumes (median 68 ml IQR 34-102 ml vs. 42 ml 16-92 ml, p = 0.036). Of the patients who met the revised mismatch criteria, 40% receiving alteplase had modified Rankin Scale (mRS) 0-1 at 3-month compared to 28% with placebo (Adjusted Odds Ratio (OR) = 2.23, CI 1.08-4.58, p = 0.028). In contrast, in the original mismatch cohort, 35% receiving alteplase had mRS 0-1 at 3-month compared to 30% with placebo (adjusted OR = 1.88, p = 0.056). CONCLUSIONS These data reinforce the benefit of alteplase in the later time window, and suggest that differences in automated perfusion imaging software outputs may be clinically relevant.