Abstract Body: Introduction
Current guidelines suggest using intravenous thrombolysis (IVT) for patients experiencing acute ischemic stroke within 4.5 hours of symptom onset. Nevertheless, recent clinical trials have explored the possibility of extending the IVT treatment window. Our aim was to identify factors influencing the treatment decision-making for extended-window intravenous thrombolysis (ewIVT) and the impact on different outcomes.

Methods
Retrospective analysis of a prospectively acquired stroke center registry of acute ischemic stroke (AIS) patients. Awakening patients or those treated between 4.5 and 9 hours from symptom onset and presenting with a LVO or positive mismatch on brain computed tomography perfusion were evaluated. We compared IVT treated and non-treated patients and identified factors related with treatment decision. Patients that underwent thrombectomy, had ASPECTS<7 or formal ESO guideline exclusion criteria were excluded. The efficacy outcomes were the 3-months modified Rankin Scale (mRS) 0-1 or return to baseline mRS and an improvement of two points in the 24hrs-NIHSS or a 24hrs-NIHSS of 0. The safety outcome was the rate of symptomatic intracranial hemorrhage (SICH).

Results
We included 79 patients (Table 1.) Twenty-two patients (27.8%) received IVT. IVT patients had similar stroke severity at baseline (median NIHSS 4.5 (2.0-6.0) vs. 4.0 (IQR 2.0-6.5); P=0.596) (Figure 1.) but presented higher ASPECTS (median 10.0 (IQR 10.0-10.0) vs. 10.0 (IQR 9.0-10.0); P=0.010) and more often had aphasia (63.6% vs. 24.6%, P=0.001). An adjusted logistic regression showed that main predictors of IVT treatment were aphasia (aOR 6.59, 95% CI 1.22-35.57; P=0.028) and favorable ASPECTS (aOR 7.05 95%CI 1.43-34.68 P=0.016). At 24 hours, 77.3% of patients in the IVT group experienced a NIHSS improvement, as compared with 36.8% in the control group (aOR 5.02, 95%CI 1.33-18.90; P=0.017). No patient in the IVT group presented with a SICH (3.6% in the control group). However, the mRS at 3 months was more favorable in the control group; 64.0% vs. 56.3% in the IVT group (aOR 0.19, 95% CI 0.03-1.19; P=0.076).

Conclusions
Presence of aphasia and ASPECTS were the main determinants of ewIVT. IVT was safe and induced early clinical improvement in AIS patients treated after 4.5 hours. Population and health-professionals’ education is crucial to promote treatment in these subgroups of patients and improve patient outcomes.