• Physiologic slowing of sinus node- sinus bradycardia
    • Atheletes
    • Expiration
  • Pathologic slowing of sinus node-
    • Sick sinus syndrome
    • SA block
  • Physiologic or pathologic parasympathetic activation- sinus bradycardia and AV block
    • Increased intracranial or intraocular pressure
    • Vasovagal reflex, carotid reflex
    • Venodilators