Predicting the success of defibrillation and cardiopulmonary resuscitation

Ventricular fibrillation (VF) remains the primary rhythm in many instances of sudden cardiac death, and defibrillation by electrical counter-shock represents the treatment of choice for this otherwise lethal arrhythmia. There is no doubt that the duration of VF remains one of the principal determinants for the likelihood of successful defibrillation. When the interval between the estimated onset of VF and the delivery of the first shock is less than 5 min, there is evidence that an immediate electrical shock would be successful [1]. When the duration of untreated VF exceeds 5 min, however, both human and animal studies demonstrate that initial CPR, with chest compression, prior to delivery of a defibrillation attempt, improves the likelihood of restoration of spontaneous circulation (ROSC) [2, 3].