Despite the proven effectiveness of intravenous thrombolysis (IVT) for patients with acute ischemic stroke (AIS) presenting within 4.5 h of symptom onset, less than 40% receive the treatment. We aimed to understand current reasons for withholding IVT to increase its administration.

We conducted a retrospective single-center analysis of AIS patients arriving within the treatment time window of 4.5 h at the hospital not undergoing IVT. 493 patients of the Swiss Stroke Registry (SSR) met the inclusion criteria between 2020 and 2022. We revisited medical records to identify the reasons for not administering IVT.

958 patients with suspicion of AIS arrived within 4.5 h at the University Hospital Zurich (USZ), 493 (51.5%) did not undergo IVT. The primary reasons for not administering IVT were mild symptoms (41.8%, n  = 167), prior use of Direct-Oral-Anticoagulants (DOACs) (27%, n  = 108), or a demarcated subacute infarction on neuroimaging (8.3%, n  = 41). Among patients with DOAC intake, specific anti-factor-Xa-(aFXa)-activity was not tested in 50% ( n  = 54). The posthoc-imaging analysis classified 41.2% ( n  = 14) of patients among the initially described demarcated infarction on NCCT as early signs of brain ischemia (EIS).

Mild symptoms and prior DOAC intake were the main reasons for withholding IVT in stroke patients arriving within the treatment time window. Furthermore, EIS on neuroimaging classified as a subacute demarcated infarction by the neuroradiologist in charge constituted another important factor to reconsider IVT among other coexisting reasons. Identification of EIS and more data about the safety of IVT despite DOAC therapy have the potential to change clinical routine and enhance the number of patients suitable for IVT.