Prognostic significance of spontaneous shockable rhythm conversion in adult out-of-hospital cardiac arrest patients with initial non-shockable heart rhythms: A systematic review and meta-analysis.

BACKGROUND: There remains controversy over the prognostic significance of spontaneous shockable rhythm conversion in out-of-hospital cardiac arrest (OHCA) patients with initial non-shockable heart rhythms (pulseless electrical activity [PEA] or asystole). The aim of this study was to examine the association of shockable rhythm conversion with multiple OHCA outcomes, and to explore effect modifiers.

METHODS: A dual-reviewer search was conducted in PubMed and EMBASE databases in March 2017. Data on study design, patient characteristics, outcomes, adjusting and stratifying variables were extracted. Estimates were combined using random-effects models.

RESULTS: Twelve studies involving 1,108,281 OHCA patients with initial non-shockable heart rhythms were identified using pre-specified eligibility criteria. Combined adjusted estimates showed that shockable rhythm conversion was associated with higher odds of pre-hospital return of spontaneous circulation (ROSC) (odds ratio [OR]=1.47, 95% confidence interval [CI] 1.40-1.55). Although shockable rhythm conversion was not associated with survival to hospital discharge (OR=1.36, 95% CI 0.77-2.38), it was associated with higher odds of one-month survival (OR=1.96, 95% CI 1.66-2.31), and one-month favourable neurological outcome (OR=2.69, 95% CI 2.00-3.62). Subgroup analyses found that shockable rhythm conversion from asystole, but not PEA, was associated with pre-hospital ROSC and survival to hospital discharge, and that earlier shockable rhythm conversions, compared to those occurring later during cardiopulmonary resuscitation, were associated with higher odds of one-month favourable neurological outcome.

CONCLUSION: Shockable rhythm conversion from initial non-shockable heart rhythms was associated with better OHCA outcomes, depending on the type of initial heart rhythm, and time of rhythm conversion.