Each year, approximately 300,000 persons in the United States experience an out-of-hospital cardiac arrest (OHCA); approximately 92% of persons who experience an OHCA event die. An OHCA is defined as cessation of cardiac mechanical activity that occurs outside of the hospital setting and is confirmed by the absence of signs of circulation. Whereas an OHCA can occur from noncardiac causes (i.e., trauma, drowning, overdose, asphyxia, electrocution, primary respiratory arrests, and other noncardiac etiologies), the majority (70%--85%) of such events have a cardiac cause. The majority of persons who experience an OHCA event, irrespective of etiology, do not receive bystander-assisted cardiopulmonary resuscitation (CPR) or other timely interventions that are known to improve the likelihood of survival to hospital discharge (e.g., defibrillation). Because nearly half of cardiac arrest events are witnessed, efforts to increase survival rates should focus on timely and effective delivery of interventions by bystanders and emergency medical services (EMS) personnel. This is the first report to provide summary data from an OHCA surveillance registry in the United States. This report summarizes surveillance data collected during October 1, 2005-- December 31, 2010. In 2004, CDC established the Cardiac Arrest Registry to Enhance Survival (CARES) in collaboration with the Department of Emergency Medicine at the Emory University School of Medicine. This registry evaluates only OHCA events of presumed cardiac etiology that involve persons who received resuscitative efforts, including CPR or defibrillation. Participating sites collect data from three sources that define the continuum of emergency cardiac care: 911 dispatch centers, EMS providers, and receiving hospitals. OHCA is defined in CARES as a cardiac arrest that occurred in the prehospital setting, had a presumed cardiac etiology, and involved a person who received resuscitative efforts, including CPR or defibrillation. During October 1, 2005--December 31, 2010, a total of 40,274 OHCA records were submitted to the CARES registry. After noncardiac etiology arrests and missing hospital outcomes were excluded from the analysis (n = 8,585), 31,689 OHCA events of presumed cardiac etiology (e.g., myocardial infarction or arrhythmia) that received resuscitation efforts in the prehospital setting were analyzed. The mean age at cardiac arrest was 64.0 years (standard deviation [SD]: 18.2); 61.1% of persons who experienced OHCA were male (n = 19,360). According to local EMS agency protocols, 21.6% of patients were pronounced dead after resuscitation efforts were terminated in the prehospital setting. The survival rate to hospital admission was 26.3%, and the overall survival rate to hospital discharge was 9.6%. Approximately 36.7% of OHCA events were witnessed by a bystander. Only 33.3% of all patients received bystander CPR, and only 3.7% were treated by bystanders with an automated external defibrillator (AED) before the arrival of EMS providers. The group most likely to survive an OHCA are persons who are witnessed to collapse by a bystander and found in a shockable rhythm (e.g., ventricular fibrillation or pulseless ventricular tachycardia). Among this group, survival to discharge was 30.1%. A subgroup analysis was performed among persons who experienced OHCA events that were not witnessed by EMS personnel to evaluate rates of bystander CPR for these persons. After exclusion of 3,400 OHCA events that occurred after the arrival of EMS providers, bystander CPR information was analyzed for 28,289 events. In this group, whites were significantly more likely to receive CPR than blacks, Hispanics, or members of other racial/ethnic populations (p<0.001). Overall survival to hospital discharge of patients whose events were not witnessed by EMS personnel was 8.5%. Of these, patients who received bystander CPR had a significantly higher rate of overall survival (11.2%) than those who did not (7.0%) (p<0.001). CARES data have helped identify opportunities for improvement in OHCA care. The registry is being used continually to monitor prehospital performance and selected aspects of hospital care to improve quality of care and increase rates of survival following OHCA. CARES data confirm that patients who receive CPR from bystanders have a greater chance of surviving OHCA than those who do not. Medical directors and public health professionals in participating communities use CARES data to measure and improve the quality of prehospital care for persons experiencing OHCA. Tracking performance longitudinally allows communities to better understand which elements of their care are working well and which elements need improvement. Education of public officials and community members about the importance of increasing rates of bystander CPR and promoting the use of early defibrillation by lay and professional rescuers is critical to increasing survival rates. Reporting at the state and local levels can enable state and local public health and EMS agencies to coordinate their efforts to target improving emergency response for OHCA events, regardless of etiology, which can lead to improvement in OHCA survival rates.
