Abstract 1: Survival Increases with CPR Before Defibrillation of Out-of-Hospital Ventricular Fibrillation or Ventricular Tachycardia: Observations from the Resuscitation Outcomes Consortium
Introduction: Immediate defibrillation is the traditional approach to resuscitation of cardiac arrest due to ventricular fibrillation or tachycardia (VF/VT). Priming the heart with compressions may enhance the efficacy of defibrillation. We estimated the effect of the duration of Emergency Medical Services (EMS) cardiopulmonary resuscitation (CPR) prior to the first defibrillation attempt on survival in a cohort of patients with out-of-hospital VF/VT in 10 sites participating in the ROC Epistry.
Methods: Prospective cohort study of non-traumatic cardiac arrest from December 2005 to October 2007. Our analysis included cases with first recorded rhythm VF/VT or “shockable.” Duration of CPR was determined by EMS provider. Multiple regression evaluated survival to hospital discharge as a function of first EMS CPR duration adjusted for age, sex, public location, bystander witnessed, bystander CPR, time to first EMS unit, and study site.
Results: Of 17,942 EMS-treated cardiac arrests, 4,010 (22%) had VF/VT/shockable rhythm. Of these, 2913 (73%) had complete data for analysis. We excluded cases witnessed by EMS (n=347) and with first CPR duration > 315 seconds (n=214). Patients were aged 0 –100 years, 77% were men, 31% occurred in public locations, and 49% received bystander CPR. Time to arrival of first EMS unit was median 7:48 (IQR 5:00, 12:06) minutes. Compared to the reference group of first CPR duration < 45 seconds, there was a strong association for greater survival with more than 46 seconds up to 195 seconds of CPR before first shock. The benefit of CPR before defibrillation was attenuated when the duration of CPR exceeded 195 seconds (Table⇓).
Conclusion: In this observational analysis, up to 195 seconds of CPR prior to defibrillation was associated with significantly improved survival of VF/VT arrest. Randomized trials are needed to evaluate this association given the potential for residual confounding in our analysis and to assess the impact on all initial rhythms.