Impact of number of passes and futile reperfusion in basilar artery occlusion acute ischaemic stroke

INTRODUCTION: Mechanical thrombectomy (MT) is the standard of care in anterior circulation large vessel occlusion. A vital modifiable factor is successful reperfusion. While multiple passes improve the rates of successful reperfusion, previous studies have reported progressively diminishing returns. This study aimed to investigate the relationship between number of passes and outcomes in basilar artery occlusion (BAO). METHODS: This multicentre retrospective cohort study included patients who were treated with MT for acute BAO from eight comprehensive stroke centres between 2015 and 2020. The primary outcome was favourable functional outcome (FFO) defined as modified Rankin Scale (mRS) 0-3 measured at 90 days. Secondary outcomes included spontaneous intracranial haemorrhage and mortality. Patients were stratified according to reperfusion status and the number of passes for further analysis. RESULTS: The adjusted odds ratio (OR) for FFO 90 days for each additional pass of a thrombectomy device was 0.56 ( P = 0.003). When ≤3 passes of the thrombectomy device were made, achieving reperfusion led to higher rates of FFOs. However, when >3 passes of the thrombectomy device were made, achieving reperfusion no longer led to higher rates of FFOs (FFO = 0% in patients who did not achieve reperfusion vs. FFO = 14.5 in patients who achieved reperfusion; P = 0.200). Notably, increasing number of passes was associated with a non-significant trend towards higher rate of parenchymal haemorrhage (OR 1.55, P = 0.055). CONCLUSION: Acute BAO patients treated with up to three passes of a thrombectomy device derived improved functional outcomes from reperfusion compared to those with more than three passes. Further prospective cohort studies are necessary to validate these findings.