Predictors of poor outcome despite recanalization: a multiple regression analysis of the NASA registry

Background Mechanical thrombectomy with stent-retrievers results in higher recanalization rates compared with previous devices. Despite successful recanalization rates (Thrombolysis in Cerebral Infarction (TICI) score 2b) of 70-83%, good outcomes by 90-day modified Rankin Scale (mRS) score 2 are achieved in only 40-55% of patients. We evaluated predictors of poor outcomes (mRS >2) despite successful recanalization (TICI 2b) in the North American Solitaire Stent Retriever Acute Stroke (NASA) registry. Methods Logistic regression was used to evaluate baseline characteristics and recanalization outcomes for association with 90-day mRS score of 0-2 (good outcome) vs 3-6 (poor outcome). Univariate tests were carried out for all factors. A multivariable model was developed based on backwards selection from the factors with at least marginal significance (p0.10) on univariate analysis with the retention criterion set at p0.05. The model was refit to minimize the number of cases excluded because of missing covariate values; the c-statistic was a measure of predictive power. Results Of 354 patients, 256 (72.3%) were recanalized successfully. Based on 234 recanalized patients evaluated for 90-day mRS score, 116 (49.6%) had poor outcomes. Univariate analysis identified an increased risk of poor outcome for age 80years, occlusion site of internal carotid artery (ICA)/basilar artery, National Institute of Health Stroke Scale (NIHSS) score 18, history of diabetes mellitus, TICI 2b, use of rescue therapy, not using a balloon-guided catheter or intravenous tissue plasminogen activator (IV t-PA), and >30min to recanalization (p0.05). In multivariable analysis, age 80years, occlusion site ICA/basilar, initial NIHSS score 18, diabetes, absence of IV t-PA, 3 passes, and use of rescue therapy were significant independent predictors of poor 90-day outcome in a model with good predictive power (c-index=0.80). Conclusions Age, occlusion site, high NIHSS, diabetes, no IV t-PA, 3 passes, and use of rescue therapy are associated with poor 90-day outcome despite successful recanalization.