• death within 1 hour of onset of any symptom


  • general population
    • 0.36–1.28 per 1,000 person-years
  • athletes
    • young athletes (< 35 years old) ranges 0.7–3 per 100,000 athletes
    • in older athletes (≥ 35 years old) reported to be higher than in young athletes and increases with increasing age

Cardiac conditions with increased risk of sudden cardiac death (SCD)

  • coronary artery disease (CAD)
  • nonischemic cardiomyopathy
  • valvular heart disease
  • congenital heart disease
  • arrhythmogenic right ventricular dysplasia
  • anomalous coronary artery origin
  • primary electrophysiologic conditions
    • congenital long QT syndrome
    • short-QT syndrome
    • Wolff-Parkinson-White syndrome
    • idiopathic ventricular fibrillation
    • Brugada syndrome
    • catecholaminergic polymorphic ventricular tachycardia (CPVT)

Possible risk factors

  • higher baseline C-reactive protein levels
  • ma huang, an herbal ephedra source
  • long-term cocaine use
  • possible genetic risk factors
    • common variant at chromosome 9p21
    • homozygosity for Gln27Glu single nucleotide polymorphism in beta-2 adrenergic receptor (ADRB2)
    • RyR2-encoded cardiac ryanodine receptor mutation
    • mutation of cardiac troponin T

Continue Reading


  • ventricular fibrillation most common cause of SCD
  • SCD may also be caused by other cardiac tachycardias, bradycardias, or pulseless electrical activity
  • commotio cordis is a phenomenon of sudden death caused by blunt nonpenetrating impact to left chest
    • 70 identified or suspected cases
    • 128 cases in US Commotio Cordis Registry
  • 69% of women with SCD have no history of cardiac disease, but most have ≥ 1 risk factor for cardiac disease


  • possible pathophysiology of SCD
    • predisposition to SCD due to stable cardiac abnormalities
    • abnormal myocardial substrate triggered by ≥1 precipitating factor
    • combination of susceptible myocardium and precipitating factor results in
      • ventricular fibrillation
      • pulseless ventricular tachycardia
      • pulseless electrical activity
      • asystole
    • sudden cardiac arrest occurs, followed by death if resuscitation not initiated and successful
  • acute coronary lesions, including plaque disruption and thrombi, reported to be found in 20%-80% of autopsies of persons with SCD

Making the diagnosis

  • natural death due to cardiac causes occurring within 1 hour of symptom onset and
    • excluding trauma as mechanism for death
    • timing and mode of death unexpected