Impact of emergency medical services on the prognosis in acute ischemic stroke patients receiving reperfusion therapy or usual treatment: a prospective cohort study

BACKGROUND: The impact of Emergency Medical Service (EMS) on the prognosis of patients with acute ischemic stroke (AIS) remains controversial. METHODS: This prospective cohort study enrolled AIS patients admitted to the emergency department of the Central Hospital of Dalian University of Technology between August 1, 2024, and July 31, 2025. Inverse probability weighting (IPW) adjusted for baseline characteristics, and modified Poisson regression determined the association between EMS transport and the primary outcome, defined as the modified Rankin Scale score of 0-1 at the 3-month follow-up. Post-hoc analyses compared differences in key clinical indicators between groups. Subgroup analyses for primary outcome explored variations among populations with distinct characteristics. RESULTS: Among the 773 patients included, 236 were in the EMS-transported group and 537 in the self-transported group. There was no significant difference between the two groups regarding the possibility of good functional recovery [weighted risk ratio (RR) = 1.37, 95% confidence intervals (CI) = 0.98-1.93]. Post hoc analysis indicated shorter onset-to-door time (ODT) but longer door-to-needle time (DNT) in the EMS-transported group. Subgroup analysis revealed the lower possibility of good functional recovery in patients with a history of coronary heart disease (weighted RR = 4.74, 95% CI = 1.83-12.32; P for interaction = 0.007) and non-smokers (weighted RR = 1.63, 95% CI = 1.11-2.40; P for interaction = 0.039) via EMS transport. CONCLUSIONS: Based on IPW, EMS-transported group showed shorter ODT and longer DNT, with no significant functional improvement. Targeted pre-hospital education and risk-stratified response mechanism within hospitals may be warranted.