Association between shockable rhythm conversion and outcomes in patients with out-of-hospital cardiac arrest and initial non-shockable rhythm, according to the cause of cardiac arrest

Objective: Conversion to shockable rhythm from an initial non-shockable rhythm is associated with good neurologic prognoses in patients with out-of-hospital cardiac arrest (OHCA). We aimed to investigate whether conversion to shockable rhythm has an association with good neurologic outcomes, according to the etiology of cardiac arrest. Methods: We conducted a nationwide, population-based, cohort study using the OHCA data from the Korea Centers for Disease Control and Prevention database in 2012–2016. We included patients with OHCA and an initial non-shockable rhythm. The primary outcome was good neurologic outcome at discharge, etiologies of arrest were categorized to medical, non-medical cause. We analyzed the effect of conversion to a shockable rhythm on outcome according to causes of cardiac arrest using multiple regression analysis. Results: Of 114,628 patients with an initial non-shockable rhythm, 25,042 (21.8%) experienced conversion to a shockable rhythm; 83,437 (72.8%) had medical causes and 31,191(27.2%) had non-medical causes. In all patients with OHCA and initial non-shockable rhythm, adjusted odds ratio (OR) of conversion for good neurologic outcome was 2.051 (95% confidence interval [CI] 1.181–2.297). The medical cause group showed an adjusted OR 1.789 (95% CI 1.586–2.019) of conversion for good neurologic outcome. In non-medical cause group, the adjusted OR of conversion was 0.644 (95% CI 0.372–1.114). Conclusion: Conversion to shockable rhythm had an association with good neurologic outcome in patients with OHCA with initial non-shockable rhythms, especially due to cardiac cause. However, rhythm conversion was not associated with better outcome in patients with non-medical causes.