Abstract Body: Background: Intravenous thrombolysis (IVT) and mechanical thrombectomy (MT) are the standard of care for select stroke patients with acute large vessel occlusion (LVO). Fibrinogen levels may drop after IVT, and a significant decrease in fibrinogen is associated with an increased risk of intracranial hemorrhage (ICH). Our Pilot study aimed to explore the relationship between fibrinogen levels and the development of ICH in MT-treated patients and whether bridging with IVT further increases that risk.

Methods: This is a prospective pilot study that enrolled adults presenting to our center with a diagnosis of LVO stroke and eligible to receive MT with or without IVT between April 2020 and May 2023. All patients consented to enrollment.

Results: Forty-one patients were enrolled. Median age was 68 years [IQR 56-79], 58.5% were females and 56.1% were black. Nineteen patients (46.3%) were treated with MT+IVT , and 22 (53.6%) were treated with MT only. There was no difference in baseline characters between both groups. Baseline fibrinogen levels were similar between MT+IVT and MT-only groups [391 vs 352 mg/dL, p=0.4]. Post MT, the MT+IVT group had lower fibrinogen levels compared to the MT-only group [224 vs 303 mg/dL, p<0.001]. Similarly, there was a significant drop in fibrinogen levels between baseline and follow-up in the MT+IVT vs MT-only group [106 vs 39.5 mg/dL, p=0.001]. Eight patients (19.5%) developed ICH; 5 (26.3%) in the MT+IVT group and 3 (13.6%) in the MT-only group. No significant differences were seen in baseline, follow-up, or change in fibrinogen levels between patients who developed ICH and those who did not. However, there was a significantly lower follow-up fibrinogen levels between patients who suffered an ICH in the MT+IVT arm compared to those without ICH in the MT arm (200 vs 301 mg/dL, p=0.006). There was also a negative correlation between the drop in fibrinogen levels and the number of MT passes (Spearman CC -0.33, p=0.03).

Conclusion: This pilot study's preliminary data show that fibrinogen depletion contributes to hemorrhagic transformation in MT-treated patients. This suggests that fibrinogen monitoring in patients undergoing MT after IVT may help identify patients with an increased risk of ICH. Larger studies are needed to explore the cost-effectiveness of monitoring fibrinogen in patients undergoing bridging therapy and the benefit of repleting fibrinogen in this patient population.