Usually because of an abrupt cerebral hypoperfusion (30-50% from baseline)
Peak age: 15-19 years of age
In younger children, usually due to seizures, breath-holding spell or cardiac disease
Exercise-induced collapse
Chest pain
Previous cardiac surgery
Family history of:
Sudden Death
Cardiac disease at early age
Unexplained deaths
Death due to single-vehicle accident
Drowning
SIDS
Sudden Death
Cardiac disease at early age
Unexplained deaths
Death due to single-vehicle accident
Drowning
SIDS
Syncope 
Seizure
Laryngospasm
Breath-holding spell
Chest pain 
Hyperventilation syndrome
Sedation 
Pregnancy 