Chapter 15: Sudden Cardiac Arrest/Sudden Cardiac Death

HISTORICAL CONSIDERATIONS, DEFINITIONS, AND EPIDEMIOLOGY OF SUDDEN CARDIAC ARREST

In 1956, Claude Beck and colleagues described a case with resuscitation from out-of-hospital sudden cardiac arrest (SCA).^1-3 The patient, a practicing physician, had long suffered from what he had self-diagnosed as indigestion. He experienced a persistent episode, went to the hospital and was diagnosed with posterolateral myocardial infarction (MI). Given the absence of treatment at that time, he was discharged, but he collapsed just outside the hospital and was retrieved. He underwent thoracotomy, open cardiac massage, then internal defibrillation and recovered.

External defibrillation (both AC and DC) was described in the middle of the twentieth century by Zoll and colleagues⁴ and independently by Gurvich in the Soviet Union.⁵ Accidents related to the electrification of society in part spurred this research.⁶ The success of external defibrillation, applied promptly upon SCA due to ventricular fibrillation (VF), fostered the development of dedicated coronary care units and ambulances equipped with defibrillators.⁶

Cardiac arrest is defined as a cessation of cardiac mechanical activity and an absence of circulation.^2,3 Focusing in on cardiovascular causes of cardiac arrest, it is helpful to subdivide cardiac arrest into medical (cardiac arrest due to cardiac or other medical cause or unknown), traumatic, drug overdose, drowning, electrocution, or asphyxia.^2,7 See Table 15-1. A subset of cardiac arrest is denoted as SCA, a term often used interchangeably with sudden cardiac death (SCD), but with the latter denoting an absence of successful resuscitation. SCD has been defined as “unexpected death without an obvious noncardiac cause occurring within 1 hour of symptom onset” if witnessed or within 24 hours of last being observed in normal or baseline health if unwitnessed.^2,8 The definition, although logical, is difficult to implement on a broad scale, and even in clinical trials, events committees struggle with classification.^9-11 A 1990 consensus conference held at the Utstein Abbey on a Norwegian island, spawned terminology bearing the abbey’s name.¹² SCA classification according to these conventions has included a number of parameters, including the following: site of cardiac arrest (home, public, or other), preceding clinical status, whether witnessed or not, precipitating event, bystander CPR, arrest before or after emergency personnel arrival, initially recorded rhythm, treatment, return of spontaneous circulation (ROSC), hospital admission and discharge outcomes, neurologic status, and others. Most studies have focused on out-of-hospital SCA, as in-hospital cardiac arrest has different epidemiology and outcomes.² Important studies have included the Resuscitation Outcomes Consortium (ROC),¹³ and the Cardiac Arrest Registry to Enhance Survival (CARES).¹⁴ The ROC investigators estimated the incidence of out-of-hospital SCA to be 110.8 per 100,000 population, or 356,500 in the US in 2015.² The Oregon Sudden Unexpected Death Study put forward a slightly lower rate of 76 per 100,000 per year, after excluding noncardiac causes.¹⁵