Sudden cardiac death (SCD) is the most common cause of cardiovascular death worldwide, accounting for approximately 300,000 deaths in the U.S. annually, although estimates have ranged from 200,000 to 450,000 deaths. Operationally, SCD is most frequently defined as a cardiac death that occurred within 1 hour of cardiac symptom onset and without another probable cause of death. Studies from epidemiological cohorts from the 1970s through the 1990s suggest...