Response to Letter Regarding Article, “Waveform Analysis–Guided Treatment Versus a Standard Shock-First Protocol for the Treatment of Out-of-Hospital Cardiac Arrest Presenting in Ventricular Fibrillation: Results of an International Randomized, Controlled Trial”

We appreciate the correspondence from Drs Ristagno and Li. We also thank them and their colleagues for their many contributions to the resuscitation literature and for the most recent in their series of work on the use of amplitude spectrum area both for the prediction of defibrillation success and as a surrogate marker for cardiopulmonary resuscitation (CPR) quality. Ventricular fibrillation (VF) has long been viewed as a ubiquitous condition best treated with immediate defibrillation, yet the evolution of our understanding of this lethal arrhythmia, the optimal timing for defibrillatory shocks, and the interaction between CPR quality and changes in the VF waveform has only recently begun to flourish. The threshold value chosen for our study1 did, as the authors of the letter suggest, have …