In patients with out-of-hospital cardiac arrest (OHCA) with an initial non-shockable rhythm, the prognostic significance of conversion to a shockable rhythm (or hereafter "conversion") during resuscitation remains unclear. We investigated whether conversion is associated with good neurologic outcome. We included patients with OHCA with medical causes and an initial non-shockable rhythm by using the national OHCA surveillance cohort database of the Korea Centers for Disease Control and Prevention for 2012~2016. The primary outcome was good neurologic outcome at hospital discharge. Of 85,602 patients with an initial non-shockable rhythm, 17.9% experienced conversion. Patients with and those without conversion had good neurologic outcome rates of 3.2% and 1.0%, respectively (p < 0.001). In multiple regression analysis, conversion was associated with good neurologic outcome (adjusted odds ratio (OR) 2.604; 95% confidence interval (CI) 2.248-3.015) in the patients with an initial non-shockable rhythm, and had the association with good neurologic outcome (adjusted OR 3.972, 95% CI 3.167-4.983) in unwitnessed patients by emergency medical services (EMS) without pre-hospital return of spontaneous circulation (ROSC) among the population. In patients with OHCA with an initial non-shockable rhythm, even if with unwitnessed arrest by EMS and no pre-hospital ROSC, continuing resuscitation needs to be considered if conversion to a shockable rhythm occurred.
Keywords: conversion; out-of-hospital cardiac arrest; pre-hospital; return of spontaneous circulation.