Abstract 161: Interfacility Transfer for Mechanical Thrombectomy - Direct to Neuroangiography or CT Angiography First?

Objective: Faster time to mechanical thrombectomy (MT) is associated with better outcome in acute stroke. In patients transferred from other hospitals where a routine CT has already ruled out hemorrhage, transfer direct to angiography (DTA) suite may reduce door to groin time compared to transfer to CT angiography (CTA) first. However, this may result in unnecessary catheter angiography if many patients would have been excluded based on CTA results. We sought to determine how often CTA and repeat head CT changed the decision to proceed to MT. Methods: An internal transfer database at a comprehensive stroke center (CSC) was used to identify patients transferred from outside facilities for consideration of mechanical thrombectomy from July 2016 to May 2017. Detailed clinical and radiographic data was extracted using a standard case report form. Results: Of 187 patients transferred for MT, 171 underwent CT +/- CTA on arrival, 5 went DTA, and 11 were admitted without imaging or intervention. Among those undergoing CT +/- CTA on arrival, MT was aborted in 110 (64%) patients. Of these, 87 (79%) were aborted directly based on imaging findings, with absence of proximal large vessel occlusion (LVO) amenable to MT being the most common reason (69%), followed by rapid clinical improvement or mild deficit (7%). MT was aborted based on imaging findings in 36% of patients with NIHSS≥10 on arrival at CSC, and in 29% of patients with NIHSS≥15. In patients with outside hospital CTA demonstrating proximal LVO (n=48), MT was aborted in 48% on CSC arrival, mostly based on imaging findings (48%) or dramatic clinical improvement (31%). Use of tPA did not substantively modify any of these findings. CSC arrival to groin puncture tended to be shorter in the patients going DTA compared to CTA (median 39 v 54 min, p=0.06). Conclusions: While transfer DTA may be associated with faster door to groin puncture times, this might result in many patients undergoing unnecessary catheter angiography who would have been excluded based on CT +/- CTA findings. Even in transferred patients with severe stroke deficits on arrival, imaging excludes about 1/3 of patients from MT.