Hemorrhagic transformation during inter-hospital transfer for thrombectomy: Incidence, associated factors, and relationship with outcome.

Background: Patients with acute ischemic stroke with a large vessel occlusion (AIS-LVO) admitted to primary stroke centers (PSC) often require inter-hospital transfer to a comprehensive stroke center (CSC) for endovascular therapy (EVT). We aimed to determine the incidence of hemorrhagic transformation (HT) occurring during transfer, the factors associated with HT, and its relationship with 3-month outcome.

Methods: We retrospectively analyzed data from two cohorts of AIS-LVO patients transferred from a PSC to a CSC for consideration of EVT. Patients were included if they had evidence of an anterior circulation AIS-LVO at the PSC and had a standard-of-care control brain imaging upon CSC arrival. HT was defined as any new hemorrhagic lesion within brain parenchyma visible on CSC admission imaging. Among HT patients, HT expansion was defined as an absolute volume increase of ⩾6 mL and a relative growth of ⩾33% between admission imaging and 24-h follow-up.

Results: Overall, 566 patients were included, of whom 31 (5.5%) experienced HT during transfer. Inter-hospital HT was independently associated with inter-hospital arterial recanalization (adjusted odds ratio (aOR) = 6.95, 95%CI 2.94-16.39), higher pre-transfer NIHSS score (aOR = 1.08, 95%CI 1.02-1.14), and longer time from symptom onset to CSC arrival (aOR = 1.09, 95%CI 1.04-1.13). HT expansion between CSC arrival and 24 h occurred in 24% of HT cases. Inter-hospital HT was independently associated with modified Rankin scale ⩾3 at 3-month (aOR = 3.54, 95%CI 1.08-11.67, p = 0.038).

Conclusion: HT during inter-hospital transfer for EVT is an uncommon event, yet is associated with a high rate of subsequent expansion and poor 3-month functional outcome. Treatments to reduce HT risk may be considered.