Introduction: Intra-arterial therapy has become standard-of-care for stroke patients with large vessel occlusions presenting within 6 hours of symptom onset. Treatment effectiveness at later times is currently unknown. Using data from the CT Perfusion (CTP) to predict Response to recanalization in Ischemic Stroke Project (CRISP), we assessed the effect of time to treatment on the probability of good outcomes.
Hypothesis: Symptom onset-to-reperfusion time is not associated with probability of favorable outcomes in patients with target mismatch who achieve reperfusion.
Methods: All patients enrolled underwent baseline CTP. For this analysis, we included data from patients with target mismatch (ratio of Tmax>6s lesion to core volume of >1.8) who achieved endovascular reperfusion. We determined reperfusion status by early follow-up MRI or CTP, or final TICI score 2b-3 if early follow-up perfusion imaging is unavailable. We defined good functional outcome (GFO) as mRS 0-2 at day 90. We assessed the probability of good outcome as a function of onset-to-reperfusion time using logistic regression, with prespecified adjustment for age and baseline NIHSS.
Results: Following intra-arterial intervention performed within 18 hours, 102 patients with target mismatch achieved reperfusion. Median onset-to-reperfusion time was 6.6 hours (IQR 5.2-9.5). In univariate analysis, onset-to-reperfusion time was not associated with GFO (p=0.19), whereas age and NIHSS were. Similarly, in multivariate analysis, age and NIHSS were associated with GFO, while onset-to-reperfusion time was not. The adjusted relative risk per hour of delay is 0.994 (95% CI 0.97-1.02). GFO was achieved in 71.4% of patients treated within 6 hours, and in 61.7% of patients treated after 6 hours.
Conclusion: The lack of significant association between onset-to-reperfusion time and GFO, and the high proportion of patients achieving good outcomes at 6-18 hours, suggest that endovascular interventions may be beneficial beyond 6 hours with a CTP target mismatch profile, supporting randomized controlled trials of endovascular therapy in the extended time window in selected patients.