Platform Presentation The Joint Annual Meeting of the Stroke Society of Australasia (SSA) and Smartstrokes 2023

Large Vessel Occlusion with Milder Severity associated with Better Collaterals and Less Harm From Thrombectomy Transfer Delays (#55)

Hannah Rowling 1 , Dominic Italiano 2 , Leonid Churilov 3 , Logesh Palanikumar 4 , Jackson Harvey 4 , Timothy Kleinig 4 , Mark Parsons 5 , Peter Mitchell 2 5 , Stephen Davis 2 5 , Nyika Kruyt 1 , Bruce Campbell 2 5 , Henry Zhao 2 5
  1. Leiden University Medical Centre, Leiden, South Holland, Netherlands
  2. Department of Medicine, The University of Melbourne, Melbourne, VIC, Australia
  3. Melbourne Medical School, The University of Melbourne, Melbourne, VIC, Australia
  4. Department of Neurology, Royal Adelaide Hospital, Adelaide, SA, Australia
  5. Royal Melbourne Hospital, Parkville, VIC, Australia

Background: Inter-hospital transfer delays for endovascular thrombectomy are associated with poorer outcomes but the harmful effects may be different for patients with milder baseline severity due to potentially better collateral circulation.

Aims: We examined whether patients with large vessel occlusion (LVO) and milder baseline severity had differences in 1) markers of collateral circulation and 2) the relative harm of transfer delays on outcome, compared to patients with clinically more severe baseline deficits.

Methods: We used in-hospital registry data from The Royal Melbourne and Royal Adelaide Hospitals to identify all directly presenting and transferred LVO patients undergoing endovascular thrombectomy, divided into those with milder baseline deficits (NIHSS <10) and severe baseline deficits (NIHSS ≥10). Baseline CT-perfusion markers of collateral circulation and the association between transfer status and functional outcome (using the 90-day modified Rankin Scale) were analysed.

Results: A total of 1210 LVO patients were included of which 273 (22.6%) had milder severity. Milder LVO patients showed smaller median ischemic core volumes (12.6 [IQR 0.0-17.9] vs 27.5 [IQR 6.5-37.1] mL, p<0.001)), higher median perfusion mismatch ratio (148.3 [IQR 5.0-500.0] vs 66.2 [IQR 3.6-17.2], p<0.001) and lower median hypoperfusion intensity ratio (0.25 [IQR 0.18-0.38] vs 0.40 [IQR 0.22-0.57], p<0.001). Transferred patients had a lower odd of excellent outcome than primary presenters, when deficits were severe deficits (aOR 0.759 [95% CI 0.576-0.999]) but not when deficits were milder (aOR 1.357 [95% CI 0.764-2.409], p-interaction=0.122).

Conclusion: Patients with LVO and milder baseline severity showed better imaging markers of collateral circulation. Secondary transfer delays for thrombectomy were only associated with poorer 90-day functional outcomes in higher-severity patients. Our results have implications for pre-hospital LVO screening tools where failure to detect lower severity LVO may not deleteriously affect outcome.