Clinical outcomes with delayed mechanical thrombectomy: Descriptive analysis and development of a screening tool.

BACKGROUND
Limited data guides selection of patients with large vessel occlusion ischaemic stroke who may benefit from referral to a distant tertiary centre for mechanical thrombectomy (MT).


METHODS
We undertook a retrospective cohort analysis enrolling patients transferred from regional sites to one of two MT comprehensive stroke units with a time from non-contrast CT Brain (NCCT) to reperfusion of four hours or more. We describe ASPECTS, National Institute of Health Stroke Scale (NIHSS) and mRS in our patients and compare the latter to the extended time window trials. Lastly, we developed and validated a scoring model to help clinicians identify appropriate patients based on variables associated with poor outcomes.


RESULTS
We included 563 patients. 46% of patients received thrombolysis; the median ASPECTS was 8 (IQR 7 to 10), median NIHSS was 16 (IQR 11 to 20). The median symptom to reperfusion time was 390 minutes (IQR 300 to 580minutes). Eight patients (1%) had a symptomatic haemorrhage. We achieved good clinical outcome (defined as mRS ≤2) in 299 patients (54%). Age, diabetes, NIHSS and ASPECT score were used to create a weighted scoring system with a validated AUC 0.83 (95% CI 0.74 to 0.92).


CONCLUSION
Our study shows in highly selected patients that delayed MT many hours after baseline NCCT is associated with good clinical outcomes. However, older patients with diabetes, high NIHSS and low ASPECTS scores may not benefit from transfer in this model of care.