- Idiopathic abnormalities that affect ion channels controlling depolarization/repolarization of heart
- Long QT syndrome (congenital)
- Brugada syndrome
- Often present with symptoms/events at young ages (< 40)
- Sometimes precipitated by athletic activity
- Lightheadedness, palpitations, racing heart, SOB
- Syncope, pre-syncope, sudden death
- Abnormalities on baseline EKG