Prehospital Cardiac Arrest: Early and Long-Term Clinical and Electrophysiologic Characteristics

Abstract

Unexpected cardiac arrest in an out-of-hospital environment is a worldwide problem of enormous magnitude. Estimates for the United States alone suggest that 300,000 to 600,000 sudden deaths occur each year, with the broad range of estimates reflecting various definitions of “sudden death” (1). Until recently, studies of the nature and characteristics of sudden death victims remained entirely in the realm of epidemiologists and pathologists, since prehospital cardiac arrest was virtually 100% fatal. The clinical characteristics of patients dying suddenly and unexpectedly in the community were derived retrospectively from pathologic data, and the electrophysiologic characteristics were speculated upon from other clinical settings. The development of community-based emergency medical systems during the past decade, however, has led to the survival of a significant percentage of prehospital cardiac arrest victims; and, at the same time, has provided clinical investigators with the ability to study the clinical and electrophysiologic characteristics of individuals who have survived an unexpected, out-of-hospital cardiac arrest (2–4). Moreover, since survivors of prehospital cardiac arrest are at high risk for a recurrent cardiac arrest (approximately 30%) in the first year after the initial event (3, 4), it is also possible to study the characteristics of patients at risk for a future event.