Abstract Body: Background: Patients with acute ischemic stroke and a large vessel occlusion (LVO) admitted to primary stroke centers (PSC) often require inter-facility transfer for thrombectomy. We aimed to study the efficacy and safety of intravenous thrombolysis (IVT) use before transfer.

Methods: We retrospectively analyzed data from two prospective cohorts of acute stroke patients with an anterior circulation LVO transferred for thrombectomy from a PSC, regardless of whether thrombectomy was eventually attempted in the endovascular-capable center. The primary efficacy outcome was good 3-month functional outcome, defined as a modified Rankin scale (mRS) 0-2. Secondary efficacy outcomes were excellent 3-month functional outcome (mRS 0-1) and arterial recanalization during transfer. Safety outcomes were any intracerebral hemorrhage (ICH) and symptomatic ICH (sICH) at 24-36hrs. We used propensity score with overlap weighting to reduce baseline differences between patients treated with IVT vs those without.

Results: A total of 521 patients were included, of whom 260 (50%) received IVT before transfer. The main reasons for withholding IVT were being outside the 4.5hr time-window (56%) and anticoagulants use (21%). Median age was 72 years, 55% were men, median baseline NIHSS was 15 and occlusion site was intracranial carotid in 21%, M1 in 61% and M2 in 18%. Good functional outcome occurred in 37% of patients. After propensity score with overlap weighting, all baseline variables were well balanced between the two groups. Compared with patients not treated with IVT, those receiving IVT more frequently had good functional outcome (OR=2.31; 95%CI 1.52-3.51; P<0.01), excellent functional outcome (OR=1.99; 1.21-3.27; P<0.01), and inter-facility recanalization (OR=5.64; 2.91-10.92; P<0.01). There were no significant between-groups differences for any ICH (OR=1.16; 0.78-1.73; P=0.47) and sICH (OR=0.65; 0.31-1.38; P=0.26).

Conclusion: IVT before inter-facility transfer for thrombectomy is associated with improved functional outcome, without safety concerns. Broadening IVT indications in PSCs may improve clinical recovery.