This nationwide Japanese cohort included 442,630 adults with out-of-hospital cardiac arrest and initial pulseless electrical activity; the primary outcome was favourable neurological outcome at one month. Witnessed arrest predicted a favourable outcome (RR 1.65), while longer response time predicted a worse outcome (RR 0.66; 10 versus 5 minutes). Prehospital return of spontaneous circulation was the strongest predictor at hospital arrival (RR 23.31). Conversion to a shockable rhythm had opposite associations by presumed aetiology: favourable in cardiac arrest (RR 1.37), but worse in non-cardiac arrest (RR 0.73).
Prehospital information may support risk stratification after arrest with initial pulseless electrical activity, but its prognostic meaning varies by presumed aetiology. These observational associations do not establish individual prognosis.
Study limitation: The abstract reports no confidence intervals or absolute neurological outcome rates, limiting assessment of precision and clinical magnitude.
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