Prognostic implications of conversion from nonshockable to shockable rhythms in out-of-hospital cardiac arrest

The prognostic significance of conversion from nonshockable to shockable rhythms in patients with initial nonshockable rhythms who experience out-of-hospital cardiac arrest (OHCA) remains unclear. We hypothesized that the neurological outcomes in those patients would improve with subsequent shock delivery following conversion to shockable rhythms and that the time from initiation of cardiopulmonary resuscitation by emergency medical services personnel to the first defibrillation (shock delivery time) would influence those outcomes. We analyzed the data of 569,937 OHCA adults with initial nonshockable rhythms. The data were collected in a nationwide Utstein-style Japanese database between 2005 and 2010. Patients were divided into subsequently shocked (n =21,944) and subsequently not-shocked (n =547,993) cohorts. The primary study endpoint was 1-month favorable neurological outcome (Cerebral Performance Categories scale, category 1 or 2). In the subsequently shocked cohort, the ratio of 1-month favorable neurological outcome was significantly higher than that in the subsequently not-shocked cohort (1.79% versus 0.60%, P