Community approaches to improve resuscitation after out-of-hospital sudden cardiac arrest.

Sudden cardiac arrest (SCA) is a major cause of mortality in North America and other westernized societies, accounting for 10% of all deaths and up to 50% of heart disease–related death.1,2 The condition is characterized by an unexpected cardiovascular collapse due to an underlying cardiac cause.3 This definition, although useful as an intellectual foundation, is challenged by operational translation. The challenge of deriving a working case definition for SCA is important because different approaches for ascertainment and classification can influence efforts aimed at estimating incidence, improving prevention strategies, or directing resuscitation care. For example, various strategies may be used to determine incidence. Death certificates, emergency medical services (EMS) records, witness interviews, medical records, and medical examiner reports can be used singly or in combination to ascertain and classify SCA. Each approach has strengths and limitations. Death certificate ascertainment and classification, for example, are efficient and can be defined by specific objective coding criteria but often overestimate incidence because the approach includes people who do not die suddenly or do not truly die from cardiac causes.4 Conversely, death certificates exclude people who were successfully resuscitated. Thus, the “best” strategy for SCA ascertainment and classification depends in large part on the intent of the effort and available resources. The present clinical summary discusses approaches to improve resuscitation of out-of-hospital SCA and therefore focuses on SCA treated by EMS. From an epidemiological perspective, EMS-treated, out-of-hospital SCA constitutes a subset of all heart disease death events. As such, it excludes in-hospital events and out-of-hospital events that either do not have an emergency response or receive a response but no EMS treatment. The latter circumstance arises typically when there are signs of prolonged, irreversible death or when there is a “do not resuscitate” request and documentation.5 Although community-specific heterogeneity exists with regard to EMS participation in SCA, investigation indicates that EMS attempts to resuscitate people with SCA in 20% of all heart disease death events, 33% of all out-of-hospital heart disease death events, and 50% of death events to which they respond.6,7 In North America and Europe, contemporary estimates reveal an incidence of 55/100 000 person-years for EMS-treated all-rhythm SCA and 15/100 000 personyears for EMS-treated ventricular fibrillation SCA.8,9 Importantly, there has been a decline in SCA incidence, and in particular ventricular fibrillation SCA, in the course of the past generation in many westernized societies that mirrors the decline in overall heart disease mortality.2,10,11 The reduction is likely multifactorial in origin and is generally attributed to improvements in primary and secondary prevention of heart disease as opposed to improvements in resuscitation outcomes.12 Thus, any community strategy to reduce the burden of SCA should continue to place substantial emphasis on prevention. A second paradigm of SCA prevention is early access to medical care after the onset of warning symptoms. Evidence indicates that up to three quarters of people who have SCA experience prodromal symptoms, most commonly chest discomfort or dyspnea, for a median of 60 minutes.13 Individuals delay activating or seeking medical care for a variety of reasons that include their understanding of the symptoms and the severity of the symptoms, with a consequence that some experience SCA. Thus, initiatives that inform and empower laypeople to access the medical system when warning symptoms occur constitute another effective prevention strategy that can decrease mortality due to SCA.14 Despite effective efforts aimed at prevention, SCA continues to occur in substantial numbers. In many instances, the EMS system is activated, and the victim receives attempted resuscitation. On the basis of estimates, nearly 200 000 people receive attempted EMS resuscitation each year in the United States and Canada. On average, only 8% who receive EMS treatment are resuscitated and subsequently discharged alive from the hospital.6 This singular average of SCA survival, however, is a poor gauge of resuscitation care for many communities because there is a remarkable variation in community-specific survival. Survival varies from 0% to 20% for all rhythm EMS-treated arrests and 0% to 45% (median 18%) for ventricular fibrillation arrest.6,8,9 The large numbers of treated SCA and the wide range of survival have potential implications for public health. In the United States and Canada, for example, an additional 7500 lives would be saved if average survival could be increased to 12%, the midway point between the current average and the community-best, all-rhythm survival estimates.6 Efforts