Cournoyer A, et al. - Researchers examined how the initial rhythm and its subsequent conversion are associated with survival following an out-of-hospital cardiac arrest (OHCA), for the general population and for extracorporeal resuscitation (E-CPR) candidates. From a registry of OHCA in Montreal, Canada, they included 6681 adult patients suffering from a non-traumatic OHCA; an initial shockable rhythm was observed in 1788 (27%), pulseless electrical activity (PEA) and no subsequent shockable rhythm in 1749 (26%), PEA and a subsequent shockable rhythm in 295 (4%), asystole and no subsequent shockable rhythm in 2694 (40%), and asystole and a subsequent shockable rhythm in 155 (2%). For all patients suffering from an OHCA, including the subset of potential E-CPR candidates, they noted a much better prognostic value of the initial rhythm than subsequent rhythms. They observed significantly lower odds of survival to hospital discharge in patients in all other groups vs patients having an initial shockable rhythm.