Early Versus Later Rhythm Analysis in Patients With Out-of-Hospital Cardiac Arrest

Study Questions:

Is survival after out-of-hospital cardiac arrest (OHCA) affected by the duration of manual cardiopulmonary resuscitation (CPR) before initial rhythm analysis?


This prospective study was performed by the Resuscitation Outcomes Consortium in 9,933 patients (mean age 67 years) with OHCA. Upon arrival of emergency medical services (EMS), the patients were randomly assigned to early rhythm analysis (30-60 seconds of CPR before rhythm analysis, n = 5,290) or delayed rhythm analysis (180 seconds of CPR before rhythm analysis, n = 4,643). The primary outcome was survival to hospital discharge with satisfactory functional status.


The median time to rhythm analysis was 42 seconds in the early-analysis group and 180 seconds in the later-analysis group. Survival to hospital discharge with satisfactory functional status was 5.9% in both groups.


The authors concluded that survival after OHCA is not improved by lengthening the amount of EMS-administered CPR from 30-60 seconds to 180 seconds before rhythm analysis.


Some (but not all) prior experimental and clinical studies have demonstrated improved outcomes after OHCA when CPR is performed for 3 minutes before rhythm analysis (and defibrillation if appropriate). This study provides strong evidence against a beneficial effect of additional CPR before initial rhythm analysis. The results suggest that there is no reason to defer rhythm analysis and defibrillation once the chest electrodes are in place.

Clinical Topics: Arrhythmias and Clinical EP, Implantable Devices, EP Basic Science, SCD/Ventricular Arrhythmias

Keywords: Out-of-Hospital Cardiac Arrest, Emergency Medical Services, Cardiopulmonary Resuscitation, Electric Countershock, Heart Arrest, Patient Discharge

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