Clinical Change During Inter-Hospital Transfer For Thrombectomy: Incidence, Associated Factors and Relationship With Outcome

Background:Patients with acute ischemic stroke with a large vessel occlusion (LVO) admitted to non endovascular-capable centers often require inter-hospital transfer for thrombectomy. We aimed to describe the incidence of substantial clinical change during transfer, the factors associated with clinical change, and its relationship with 3-month outcome.Methods:We analyzed data from two cohorts of acute stroke patients transferred for thrombectomy to a comprehensive center (Stanford, USA, Nov 2019 to Jan 2023; Montpellier, France, Jan 2015 to Jan 2017), regardless of whether thrombectomy was eventually attempted. Patients were included if they had evidence of an LVO at the referring hospital and had an NIHSS score documented before and immediately after transfer. Inter-hospital clinical change was categorized as improvement (>=4 points and >=25% decrease between the NIHSS score in the referring hospital and upon comprehensive center arrival), deterioration (>=4 points and >=25% increase), or stability (neither improvement nor deterioration). The stable group was considered as the reference, and was compared to the improvement or deterioration groups separately.Results:A total of 504 patients were included, of whom 22% experienced inter-hospital improvement, 14% deterioration, and 64% were stable. Pre-transfer variables independently associated with clinical improvement were intravenous thrombolysis use, more distal occlusions, and lower serum glucose; variables associated with deterioration included more proximal occlusions and higher serum glucose. On post-transfer imaging, clinical improvement was associated with arterial recanalization and smaller infarct growth; and deterioration with larger infarct growth. As compared to stable patients, those with clinical improvement had better 3-month functional outcome (adjusted cOR=2.43; 95%CI 1.59-3.71; P<0.001), while those with deterioration had worse outcome (adjusted cOR=0.60; 95%CI 0.37-0.98; P=0.044).Conclusions:Substantial inter-hospital clinical changes are frequently observed in LVO-related ischemic strokes, with significant impact on functional outcome. There is a need to develop treatments that improves the clinical status during transfer.