What are the causes of sudden cardiac death (SCD) in patients with structurally normal hearts?

Causes of sudden cardiac death in patients with structurally normal hearts

• lon channel diseases of the heart such as long QT syndrome or Brugada's syndrome 
• Accessory pathways such as Wolf--Parkinson--White syndrome 
• Commotio Cordis 
• Focal myocarditis 
• Atypical right ventricular cardiomyopathy that may not be recognized by the pathologist 
• Drugs such as amphetamines 
• Electrolyte disturbances

[Source: Rapid review of clinical medicine for MRCP part 2, 2nd Edition, by Sanjay Sharma and Rashmi Kaushal; Question 353]