Structural Associations and Causes

1. Coronary heart disease (chronic, or acute coronary syndromes)
2. Myocardial hypertrophy (e.g., hypertrophic cardiomyopathy)
3. Dilated cardiomyopathy
4. Inflammatory (e.g., myocarditis) and infiltrative disorders
5. Valvular heart diseases
6. Electrophysiologic abnormalities (e.g., Wolff-Parkinson-White syndrome)
7. Inherited disorders associated with electrophysiological abnormalities (e.g., congenital long QT syndromes, right ventricular dysplasia, Brugada syndrome, catecholaminergic polymorphic ventricular tachycardia)

Functional Contributing Factors

1. Transient ischemia
2. Low cardiac output states (heart failure, shock)
3. Systemic metabolic abnormalities
   1. Electrolyte imbalance (e.g., hypokalemia)
   2. Hypoxemia, acidosis
4. Neurologic disturbances (e.g., CNS injury)
5. Toxic responses
   1. Proarrhythmic drug effects
   2. Cardiac toxins (e.g., cocaine, digitalis intoxication)