Dynamics and state transitions during resuscitation in out-of-hospital cardiac arrest

Background: The state or rhythm during resuscitation, i.e. ventricular fibrillation/tachycardia (VF/VT), asystole (ASY), pulseless electrical. activity (PEA), or return of spontaneous circulation (ROSC) determines management. The state is unstable and will. change either spontaneously (e.g. PEA -> ASY) or by intervention (e.g. VF -> ASY after DC shock); temporary ROSC may also occur. To gain insight into the dynamics of this process, we analyzed the state transitions over time using real-life data. Methods: Detailed recordings from 304 episodes of attempted resuscitation from out-of-hospital cardiac arrests of presumed cardiac etiology were obtained from modified Heartstart (R) 4000 defibrillators. State transitions were visualized and described, and analyzed in terms of a Markov probability model. Results: The median number of state transitions was 5 (range 1-39), and more transitions were observed with VF than PEA or asystole as the initial rhythm. Of 105 patients (35%) who regained ROSC at some point during CPR, only 65 (21 %) achieved sustained ROSC; suggesting an unrealized survival potential. A 3-min transition probability matrix was estimated: for example, a patient early in VF has a probability of 31% to be in ASY, 32% of still being in VF, 5% to have temporary ROSC, and 2% to have sustained ROSC after 3 min. Conclusion: The dynamics of resuscitation can be described in terms of state transitions and a Markov probability model. This framework enables prediction of short-term clinical development, supports informed decisions during CPR, and suggests a novel area for research. (c) 2008 Elsevier Ireland Ltd. All rights reserved.