Early versus later rhythm analysis in patients with out-of-hospital cardiac arrest

Abstract

Background: In a departure from the previous strategy of immediate defibrillation, the 2005 resuscitation guidelines from the American Heart Association-International Liaison Committee on Resuscitation suggested that emergency medical service (EMS) personnel could provide 2 minutes of cardiopulmonary resuscitation (CPR) before the first analysis of cardiac rhythm. We compared the strategy of a brief period of CPR with early analysis of rhythm with the strategy of a longer period of CPR with delayed analysis of rhythm.

Methods: We conducted a cluster-randomized trial involving adults with out-of-hospital cardiac arrest at 10 Resuscitation Outcomes Consortium sites in the United States and Canada. Patients in the early-analysis group were assigned to receive 30 to 60 seconds of EMS-administered CPR and those in the later-analysis group were assigned to receive 180 seconds of CPR, before the initial electrocardiographic analysis. The primary outcome was survival to hospital discharge with satisfactory functional status (a modified Rankin scale score of ≤3, on a scale of 0 to 6, with higher scores indicating greater disability).

Results: We included 9933 patients, of whom 5290 were assigned to early analysis of cardiac rhythm and 4643 to later analysis. A total of 273 patients (5.9%) in the later-analysis group and 310 patients (5.9%) in the early-analysis group met the criteria for the primary outcome, with a cluster-adjusted difference of -0.2 percentage points (95% confidence interval, -1.1 to 0.7; P=0.59). Analyses of the data with adjustment for confounding factors, as well as subgroup analyses, also showed no survival benefit for either study group.

Conclusions: Among patients who had an out-of-hospital cardiac arrest, we found no difference in the outcomes with a brief period, as compared with a longer period, of EMS-administered CPR before the first analysis of cardiac rhythm. (Funded by the National Heart, Lung, and Blood Institute and others; ROC PRIMED ClinicalTrials.gov number, NCT00394706.).

Figure 1. Subgroup Analyses of the Primary Outcome

Shown are the results of analyses of the primary outcome (survival to hospital discharge with a score on the modified Rankin scale of ≤3, on a scale of 0 to 6, with higher scores indicating greater disability), according to prespecified subgroups and post hoc exploratory subgroups. The impedance threshold device (ITD) study group refers to a concurrent study (involving most of the patients who were enrolled in this study), in which the use of an active ITD during cardiopulmonary resuscitation (CPR) was compared with the use of a sham ITD. The abbreviation mITT denotes modified intention to treat, VF ventricular fibrillation, and VT ventricular tachycardia.

Figure 2. Rate of the Primary Outcome, According to Actual Time to Analysis of Cardiac Rhythm

The primary outcome was survival to hospital discharge with a score on the modified Rankin scale of 3 or less. The rate of the primary outcome is shown according to the actual time to the analysis of cardiac rhythm, regardless of the study group, among patients who received cardiopulmonary resuscitation (CPR) from a bystander (Panel A) and among patients who did not receive CPR from a bystander (Panel B). In each panel, the rates are shown for patients in whom the first rhythm was ventricular fibrillation (VF) or ventricular tachycardia (VT) (thick solid lines, with 95% confidence intervals indicated by thin solid lines) and for patients in whom the first rhythm was neither VF nor VT (thick broken lines, with 95% confidence intervals indicated by thin broken lines).