Emergency medical services (EMS) response time is one of prehospital factors associated with survival rate of patients with out-of-hospital cardiac arrest (OHCA). The objective of this study was to determine whether short EMS response time was associated with improved neurologic outcome of patients with OHCA through prospective analysis.

We performed a prospective observational analysis of collected data from KoCARC registry between October 2015 and December 2016. OHCA patients aged 18 years or older with presumed cardiac etiology by emergency physicians in emergency department were included in this study.

Of 3187 cardiac arrest patients enrolled in the KoCARC registry, 2309 patients were included in the final analysis. Response time threshold was 11.5 min for prehospital return of spontaneous circulation and 7.5 min for survival to discharge and favorable neurologic outcome. Patients in the ≤7.5 min response time group showed increased odds of survival to discharge (OR: 1.54, 95% CI: 1.13–2.10, p = .006) and favorable neurologic recovery (OR: 2.01, 95% CI: 1.36–2.99, p = .001). When response time was decreased by 1 min, all outcomes were improved (survival to discharge, OR: 1.08; 95% CI: 1.04–1.12, p < .001; favorable neurological outcome, OR: 1.14, 95% CI: 1.07–1.21, p < .001).

We found that shorter EMS response time could lead to favorable neurologic outcome in patients with OHCA of presumed cardiac origin. EMS response time threshold associated with improved favorable outcome was ≤7.5 min.