Timing and Relevance of Clinical Improvement After Mechanical Thrombectomy in Patients With Acute Ischemic Stroke.

Background and Purpose- The clinical course in patients with ischemic stroke treated with mechanical thrombectomy (MT) is heterogeneous. We aimed to study the relevance of the timing of clinical improvement in the prediction of long-term outcome in patients treated with MT. Methods- We studied a cohort of 423 patients with anterior circulation stroke treated with MT, of whom 334 patients (79.0%) achieved good outcome (modified Rankin Scale score of 0-2 at 90-day follow-up). National Institutes of Health Stroke Scale scores were assessed before MT, at the end of MT (d0), at day 1 (d1), and at day 7 or discharge (d7). We explored the predictive value for good outcome of different cutoffs based on absolute and percentage changes in the National Institutes of Health Stroke Scale at each assessment (d0, d1, and d7) and selected the corresponding most informative cutoffs to define substantial clinical improvement (SCI) over time. Then, we classified patients in SCI subgroups according to the delay from MT to SCI (SCI-d0, SCI-d1, and SCI-d7) and analyzed their adjusted odds ratio for good outcome compared with patients not presenting SCI (no-SCI). Additionally, we identified the independent factors predicting SCI-d0 in multivariate models. Results- The most informative cutoffs were 30% at d0, 40% at d1, and 70% at d7. The adjusted odds ratios (95% CI) for good outcome were 47.4 (22.1-101.7, n=172) for SCI-d0, 27.7 (11.8-65.0, n=76) for SCI-d1, and 12.6 for SCI-d7 (95% CI, 3.8-41.4, n=17) compared with no-SCI (n=158). The independent factors predicting SCI-d0 were successful reperfusion (odds ratio, 25.79; 95% CI, 12.92-51.47) and shorter time to treatment (odds ratio per hour 0.90; 95% CI, 0.85-0.96). Conclusions- Shorter delay to clinical improvement is strongly related to better chances of a long-term good outcome, and an improvement >30% in National Institutes of Health Stroke Scale score at the end of MT represents a reliable prognostic marker for clinicians and also for clinical research.