Understanding Etiologies of Cardiac Arrest: Seeking Definitional Clarity.

Cardiac arrest leading to death and sudden cardiac death (SCD) may refer implicitly to situations in which death is unexpected and primarily of cardiac cause. National and international societies have published differing definitions for the various terms relating to cardiac arrest and SCD. We highlight the controversies in defining SCD, including the lack of a universal definition, the heterogeneity in the operationalization of the term "sudden," and limitations of time-based systems of SCD classification. We discuss the importance of a standardized methodology for classifying cardiac arrest as recommended by the World Health Organization (WHO) that should include use of multisource evidence (eg, coroner, autopsy, and toxicology reports) for confirming or refuting a cardiac cause of arrest. We reveal how a universal definition of SCD has been incorrectly attributed to the WHO and how this has been perpetuated in the literature. We make the case that definitional clarity is essential to understanding epidemiology, evaluating novel treatments, forming international collaboration, and innovating public health prevention strategies. We propose a practical schema to categorize cardiac arrest events to describe and study this population more accurately.