The best timing for defibrillation in shockable cardiac arrest

High quality cardiopulmonary resuscitation (CPR, i.e. chest compressions and ventilations) and prompt defibrillation when appropriate (i.e. in ventricular fibrillation and pulseless ventricular tachycardia, VF/VT) are currently the best early treatment for cardiac arrest (CA). In cases of prolonged CA due to shockable rhythms, it is reasonable to presume that a period of CPR before defibrillation could partially revert the metabolic and hemodynamic deteriorations imposed to the heart by the no flow state, thus increasing the chances of successful defibrillation. Despite supporting early evidences in CA cases in which Emergency Medical System response time was longer than 5 minutes, recent studies have failed to confirm a survival benefit of routine CPR before defibrillation. These data have imposed a change in guidelines from 2005 to 2010. To take in account all the variables encountered when treating CA (heart condition before CA, time elapsed, metabolic and hemodynamic changes, efficacy of CPR, responsiveness to defibrillation attempt), it would be very helpful to have a real-time and non invasive tool able to predict the chances of defibrillation success. Recent evidences have suggested that ECG waveform analysis of VF, such as the derived Amplitude Spectrum Area, can fit the purpose of monitoring the CPR effectiveness and predicting the responsiveness to defibrillation. While awaiting clinical studies confirming this promising approach, CPR performed according to high quality standard and with minimal interruptions together with early defibrillation are the best immediate way to achieve resuscitation in CA due to shochable rhythms..