Seizure
Breath-holding spell
Hyperventilation syndrome
Pregnancy (especially ectopic)
Hypoglycemia
Cardiac disease
Tet spell
Hypertrophic cardiomyopathy
Brugada Syndrome
Dysrhythmias
Long QT syndrome
Anomalous coronary arteries
Toxicologic exposure (stimulants or depressant)
CO poisoning
Ethanol toxicity
Drugs of abuse
Tet spell
Hypertrophic cardiomyopathy
Brugada Syndrome
Dysrhythmias
Long QT syndrome
Anomalous coronary arteries
CO poisoning
Ethanol toxicity
Drugs of abuse
Syncope 
Seizure
Laryngospasm
Breath-holding spell
Chest pain 
Hyperventilation syndrome
Sedation 
Pregnancy 