Abstract Body: Background
Endovascular treatment (EVT) is an effective treatment for acute ischemic stroke in anterior large vessel occlusions. Despite successful reperfusion, many patients still have unfavorable outcomes even in the presence of favorable arterial collaterals. We determined patient characteristics, treatment details and imaging characteristics associated with favorable outcome in patients with good collaterals who had successful EVT.

Methods
In a post hoc analysis of the prospective CRISP 2 study, we identified patients with successful reperfusion following EVT (TICI 2b-3) and good collaterals (Tan ≥2). These patients were dichotomized into favorable (mRS 0-2) and unfavorable outcome (mRS 3-6) groups. Multivariate analyses were performed to identify clinical, imaging, and treatment predictors of favorable outcome.

Results
92 patients were included, and 31 patients (33.7%) had favorable outcomes. There were no differences in the number of females (16 patients [52%] versus 33 patients [54%]; p=0.821) or age (71 years, [IQR 56-79] versus 68 years [IQR 57-79]; p=0.859) in favorable versus unfavorable groups, respectively. Favorable outcome patients had lower pre-treatment mRS (p<0.001), more frequent administration of intravenous thrombolysis (52% versus 23%; p=0.006), shorter EVT procedure times (27 min (IQR 23-40) versus 46 min (IQR 27-64), and lower NIHSS before EVT (12 [IQR 9-15] versus 16 [IQR 12-20]; p=0.006). There were no differences in the frequency of TICI 3 rates (48% vs. 38%; p=0.325) or first pass effect between the two groups (61% vs. 57%; p=0.719). In a multivariable regression analysis, intravenous thrombolysis administration (OR 3.27 [95% CI: 1.04-10.33]; p = 0.043) and EVT procedure time (OR for every 5 min 0.98 [95% CI: 0.81-0.98]; p = 0.022) were modifiable predictors of favorable outcomes. Lower pre-stroke mRS also predicted favorable outcomes (p = 0.03).

Conclusions
Among patients with good collaterals and successful reperfusion following EVT, favorable outcomes were associated with lower baseline mRS, intravenous thrombolysis administration, and shorter EVT procedure times.