Published Online
on November 10, 2009

A more recent version of this article appeared on January 1, 2010

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Original Article

Predictors of Survival From Out-of-Hospital Cardiac Arrest

A Systematic Review and Meta-Analysis

Comilla Sasson, MD, MS; Mary A.M. Rogers, MS, PhD; Jason Dahl, MD and Arthur L. Kellermann, MD, MPH

From the Departments of Emergency Medicine (C.S.) and Internal Medicine (M.A.M.R.), University of Michigan, Ann Arbor; the University of Rochester (J.D.), NY; and the Department of Emergency Medicine (A.L.K.), Emory University, Atlanta, Ga.

Correspondence to Comilla Sasson, MD, MS, Robert Wood Johnson Clinical Scholars Program, 1150 W Medical Center Dr, 6312 Medical Science Building 1, Campus Box 5604. Ann Arbor, MI 48109. E-mail comilla{at}umich.edu

Background: Prior studies have identified key predictors of out-of-hospital cardiac arrest (OHCA), but differences exist in the magnitude of these findings. In this meta-analysis, we evaluated the strength of associations between OHCA and key factors (event witnessed by a bystander or emergency medical services [EMS], provision of bystander cardiopulmonary resuscitation [CPR], initial cardiac rhythm, or the return of spontaneous circulation). We also examined trends in OHCA survival over time.

Methods and Results: An electronic search of PubMed, EMBASE, Web of Science, CINAHL, Cochrane DSR, DARE, ACP Journal Club, and CCTR was conducted (January 1, 1950 to August 21, 2008) for studies reporting OHCA of presumed cardiac etiology in adults. Data were extracted from 79 studies involving 142 740 patients. The pooled survival rate to hospital admission was 23.8% (95% CI, 21.1 to 26.6) and to hospital discharge was 7.6% (95% CI, 6.7 to 8.4). Stratified by baseline rates, survival to hospital discharge was more likely among those: witnessed by a bystander (6.4% to 13.5%), witnessed by EMS (4.9% to 18.2%), who received bystander CPR (3.9% to 16.1%), were found in ventricular fibrillation/ventricular tachycardia (14.8% to 23.0%), or achieved return of spontaneous circulation (15.5% to 33.6%). Although 53% (95% CI, 45.0% to 59.9%) of events were witnessed by a bystander, only 32% (95% CI, 26.7% to 37.8%) received bystander CPR. The number needed to treat to save 1 life ranged from 16 to 23 for EMS-witnessed arrests, 17 to 71 for bystander-witnessed, and 24 to 36 for those receiving bystander CPR, depending on baseline survival rates. The aggregate survival rate of OHCA (7.6%) has not significantly changed in almost 3 decades.

Conclusions: Overall survival from OHCA has been stable for almost 30 years, as have the strong associations between key predictors and survival. Because most OHCA events are witnessed, efforts to improve survival should focus on prompt delivery of interventions of known effectiveness by those who witness the event.

Key Words: heart arrest • death, sudden • emergency medical services