Early versus Later Rhythm Analysis in Patients with Out-of-Hospital Cardiac Arrest
Out-of-hospital cardiac arrest is a common and lethal problem, leading to an estimated 330,000 deaths each year in the United States and Canada. Overall, the rate of survival to hospital discharge among patients with an out-of-hospital cardiac arrest who are treated by emergency medical services (EMS) personnel is low but varies greatly, with rates ranging from 3.0% to 16.3%. This variation in the rate of survival can be attributed partly to local variations in the five key links in the chain of survival: rapid EMS access, early cardiopulmonary resuscitation (CPR), early defibrillation, early advanced cardiac life support, and effective care after resuscitation. Concerted efforts by EMS personnel to strengthen these links have led to only a slight increase in survival rates in recent years.
Malegra
The traditional approach to out-of-hospital cardiac arrest has been to emphasize early analysis of cardiac rhythm, with delivery of defibrillatory shocks, if indicated, as quickly as possible. It has been suggested, however, that many patients may benefit from a period of CPR before the first analysis of rhythm. The 2005 resuscitation guidelines from the American Heart Association–International Liaison Committee on Resuscitation (AHA–ILCOR) departed from its previous “shock first” strategy by suggesting that responders could provide 2 minutes of CPR before analysis of cardiac rhythm. These changes in the guidelines are supported by the findings of three clinical studies but are not supported by two others, and in the 2010 guidelines, the recommendation was modified to say that “there is inconsistent evidence to support or refute” such a delay in the analysis of cardiac rhythm. Therefore, the preferred initial approach remains uncertain. Our objective was to compare two approaches to the timing of CPR by EMS personnel — a brief period of manual chest compressions and ventilations with prompt initiation of rhythm analysis and defibrillation (early analysis) versus a longer period of compressions and ventilations before the first analysis of cardiac rhythm (later analysis).
Study Design and Oversight
A detailed description of the methods has been published previously. The Resuscitation Outcomes Consortium (ROC) is a clinical trial consortium comprising 10 U.S. and Canadian universities and their regional EMS systems. The ROC investigators designed the Prehospital Resuscitation Impedance Valve and Early Versus Delayed Analysis (ROC PRIMED) trial to study two randomized comparisons. The first comparison, in which early analysis of cardiac rhythm was compared with later rhythm analysis, is the subject of this article. The second, concurrent comparison, in which the use of an impedance threshold device (ITD) was compared with the use of a sham ITD, is reported elsewhere in this issue of the Journal. Most patients were enrolled simultaneously in both the early-analysis-versus-later-analysis component and the active-ITD-versus-sham-ITD component of the ROC PRIMED trial, although the two components had slightly different eligibility criteria.